From 560c9fbff3b80ea8f79192db3c2728356d2ae4a6 Mon Sep 17 00:00:00 2001
From: soky srm <sokysrm@gmail.com>
Date: Wed, 25 Mar 2026 10:50:23 +0100
Subject: [PATCH] Family sharing (#1272)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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* Initial account sharing changes

* Update schema.rb

* Update schema.rb

* Change sharing UI to modal

* UX fixes and sharing controls

* Scope include in finances better

* Update totals.rb

* Update totals.rb

* Scope reports to finance account scope

* Update impersonation_sessions_controller_test.rb

* Review fixes

* Update schema.rb

* Update show.html.erb

* FIX db validation

* Refine edit permissions

* Review items

* Review

* Review

* Add application level helper

* Critical review

* Address remaining review items

* Fix modals

* more scoping

* linter

* small UI fix

* Fix: Sync broadcasts push unscoped balance sheet to all users

* Update sync_complete_event.rb

 The fix removes the sidebar broadcasts (which rendered unscoped account groups using family.balance_sheet without user context)
  along with the now-unused sidebar_targets, account_group, and family_balance_sheet private methods.

  The sidebar will still update correctly — when the sync completes, Family::SyncCompleteEvent#broadcast fires family.broadcast_refresh, which triggers a
  morph-based page refresh for each user with their own authenticated session, rendering properly scoped sidebar content.
---
 app/components/DS/dialog.html.erb             |   2 +-
 .../account_sharings_controller.rb            |  62 ++++
 app/controllers/accounts_controller.rb        |  21 +-
 app/controllers/application_controller.rb     |  10 +
 .../concerns/accountable_resource.rb          |  32 +-
 .../concerns/entryable_resource.rb            |  32 +-
 app/controllers/holdings_controller.rb        |  20 +-
 app/controllers/import/uploads_controller.rb  |   4 +-
 app/controllers/imports_controller.rb         |   4 +-
 app/controllers/pages_controller.rb           |  12 +-
 .../pending_duplicate_merges_controller.rb    |   8 +-
 app/controllers/properties_controller.rb      |  16 +-
 app/controllers/reports_controller.rb         |  53 ++--
 app/controllers/splits_controller.rb          |  10 +-
 app/controllers/trades_controller.rb          |  34 ++-
 .../transaction_attachments_controller.rb     |  22 +-
 .../transaction_categories_controller.rb      |   9 +-
 .../transactions/bulk_deletions_controller.rb |  18 +-
 app/controllers/transactions_controller.rb    | 103 ++++++-
 .../transfer_matches_controller.rb            |  14 +-
 app/controllers/transfers_controller.rb       |  49 ++-
 app/controllers/users_controller.rb           |  15 +-
 app/controllers/valuations_controller.rb      |  40 ++-
 app/models/account.rb                         |  75 ++++-
 app/models/account/sync_complete_event.rb     |  35 ---
 app/models/account_share.rb                   |  47 +++
 app/models/balance_sheet.rb                   |  11 +-
 app/models/balance_sheet/account_totals.rb    |  28 +-
 .../balance_sheet/classification_group.rb     |   2 +-
 .../balance_sheet/net_worth_series_builder.rb |  14 +-
 app/models/current.rb                         |  15 +
 app/models/family.rb                          |  18 +-
 app/models/family/sync_complete_event.rb      |  27 +-
 app/models/income_statement.rb                |  22 +-
 app/models/income_statement/category_stats.rb |   9 +-
 app/models/income_statement/family_stats.rb   |   9 +-
 app/models/income_statement/totals.rb         |  17 +-
 app/models/investment_flow_statement.rb       |  13 +-
 app/models/investment_statement.rb            |  19 +-
 app/models/invitation.rb                      |  10 +
 app/models/transaction/search.rb              |  11 +-
 app/models/user.rb                            |  28 ++
 app/policies/account_policy.rb                |  38 +++
 app/views/account_sharings/show.html.erb      |  92 ++++++
 app/views/accounts/_account.html.erb          |  34 ++-
 .../accounts/_accountable_group.html.erb      |   3 +
 app/views/accounts/index/_account_groups.erb  |   1 +
 app/views/accounts/show/_activity.html.erb    |  42 +--
 app/views/accounts/show/_header.html.erb      |   3 +
 app/views/accounts/show/_menu.html.erb        |  42 +--
 app/views/imports/new.html.erb                |   2 +-
 app/views/pages/dashboard.html.erb            |   3 +-
 app/views/settings/preferences/show.html.erb  |  19 ++
 app/views/trades/_form.html.erb               |   2 +-
 .../create.turbo_stream.erb                   |   2 +-
 .../destroy.turbo_stream.erb                  |   2 +-
 app/views/transactions/_attachments.html.erb  |  24 +-
 app/views/transactions/_form.html.erb         |   2 +-
 .../searches/filters/_account_filter.html.erb |   2 +-
 app/views/transactions/show.html.erb          | 288 +++++++++---------
 config/locales/views/account_sharings/en.yml  |  29 ++
 config/locales/views/accounts/en.yml          |   2 +
 config/locales/views/settings/en.yml          |   5 +
 config/routes.rb                              |   2 +
 ...60324100000_add_account_sharing_support.rb |  21 ++
 ...0001_backfill_account_owners_and_shares.rb |  34 +++
 ...dd_check_constraints_to_sharing_columns.rb |   6 +
 ...003_change_accounts_owner_fk_to_nullify.rb |  11 +
 db/schema.rb                                  |  27 +-
 .../impersonation_sessions_controller_test.rb |   2 +-
 .../transactions_controller_test.rb           |   4 +-
 test/fixtures/account_shares.yml              |  13 +
 test/fixtures/accounts.yml                    |  10 +
 test/models/account_share_test.rb             |  61 ++++
 test/models/account_test.rb                   |  93 ++++++
 75 files changed, 1520 insertions(+), 401 deletions(-)
 create mode 100644 app/controllers/account_sharings_controller.rb
 create mode 100644 app/models/account_share.rb
 create mode 100644 app/policies/account_policy.rb
 create mode 100644 app/views/account_sharings/show.html.erb
 create mode 100644 config/locales/views/account_sharings/en.yml
 create mode 100644 db/migrate/20260324100000_add_account_sharing_support.rb
 create mode 100644 db/migrate/20260324100001_backfill_account_owners_and_shares.rb
 create mode 100644 db/migrate/20260324100002_add_check_constraints_to_sharing_columns.rb
 create mode 100644 db/migrate/20260324100003_change_accounts_owner_fk_to_nullify.rb
 create mode 100644 test/fixtures/account_shares.yml
 create mode 100644 test/models/account_share_test.rb

diff --git a/app/components/DS/dialog.html.erb b/app/components/DS/dialog.html.erb
index 3487ed89e..307303970 100644
--- a/app/components/DS/dialog.html.erb
+++ b/app/components/DS/dialog.html.erb
@@ -2,7 +2,7 @@
   <%= tag.dialog class: "w-full h-full bg-transparent theme-dark:backdrop:bg-alpha-black-900 backdrop:bg-overlay pt-[env(safe-area-inset-top)] pb-[env(safe-area-inset-bottom)] #{(drawer? || responsive?) ? "lg:p-3" : "lg:p-1"}", **merged_opts do %>
     <%= tag.div class: dialog_outer_classes do %>
       <%= tag.div class: dialog_inner_classes, data: { DS__dialog_target: "content" } do %>
-        <div class="grow py-4 space-y-4 flex flex-col <%= 'overflow-auto' if scrollable %>">
+        <div class="grow py-4 space-y-4 flex flex-col <%= "overflow-auto" if scrollable %>">
           <% if header? %>
             <%= header %>
           <% end %>
diff --git a/app/controllers/account_sharings_controller.rb b/app/controllers/account_sharings_controller.rb
new file mode 100644
index 000000000..f04bcee6e
--- /dev/null
+++ b/app/controllers/account_sharings_controller.rb
@@ -0,0 +1,62 @@
+class AccountSharingsController < ApplicationController
+  before_action :set_account
+
+  def show
+    @family_members = Current.family.users.where.not(id: @account.owner_id).where(active: true)
+    @account_shares = @account.account_shares.includes(:user).index_by(&:user_id)
+  end
+
+  def update
+    # Non-owners can update their own include_in_finances preference
+    if !@account.owned_by?(Current.user) && params[:update_finance_inclusion].present?
+      share = @account.account_shares.find_by!(user: Current.user)
+      include_value = params.permit(:include_in_finances)[:include_in_finances]
+      share.update!(include_in_finances: ActiveModel::Type::Boolean.new.cast(include_value))
+      redirect_back_or_to account_path(@account), notice: t("account_sharings.update.finance_toggle_success")
+      return
+    end
+
+    unless @account.owned_by?(Current.user)
+      redirect_to account_path(@account), alert: t("account_sharings.update.not_owner")
+      return
+    end
+
+    eligible_members = Current.family.users.where.not(id: @account.owner_id).where(active: true)
+
+    AccountShare.transaction do
+      sharing_members_params.each do |member_params|
+        user = eligible_members.find_by(id: member_params[:user_id])
+        next unless user
+
+        share = @account.account_shares.find_by(user: user)
+
+        if ActiveModel::Type::Boolean.new.cast(member_params[:shared])
+          permission = AccountShare::PERMISSIONS.include?(member_params[:permission]) ? member_params[:permission] : (share&.permission || "read_only")
+          if share
+            share.update!(permission: permission)
+          else
+            @account.account_shares.create!(user: user, permission: permission, include_in_finances: true)
+          end
+        elsif share
+          share.destroy!
+        end
+      end
+    end
+
+    redirect_back_or_to accounts_path, notice: t("account_sharings.update.success")
+  end
+
+  private
+
+    def set_account
+      @account = Current.user.accessible_accounts.find(params[:account_id])
+    end
+
+    def sharing_members_params
+      return [] unless params.dig(:sharing, :members)
+
+      params.require(:sharing).permit(
+        members: [ :user_id, :shared, :permission ]
+      )[:members]&.values || []
+    end
+end
diff --git a/app/controllers/accounts_controller.rb b/app/controllers/accounts_controller.rb
index 5fcb3df66..60dc96853 100644
--- a/app/controllers/accounts_controller.rb
+++ b/app/controllers/accounts_controller.rb
@@ -1,10 +1,15 @@
 class AccountsController < ApplicationController
-  before_action :set_account, only: %i[sync sparkline toggle_active set_default remove_default show destroy unlink confirm_unlink select_provider]
+  include StreamExtensions
+
+  before_action :set_account, only: %i[show sparkline sync set_default remove_default]
+  before_action :set_manageable_account, only: %i[toggle_active destroy unlink confirm_unlink select_provider]
   include Periodable
 
   def index
+    @accessible_account_ids = Current.user.accessible_accounts.pluck(:id)
     @manual_accounts = family.accounts
           .listable_manual
+          .where(id: @accessible_account_ids)
           .order(:name)
     @plaid_items = family.plaid_items.ordered.includes(:syncs, :plaid_accounts)
     @simplefin_items = family.simplefin_items.ordered.includes(:syncs)
@@ -200,7 +205,19 @@ class AccountsController < ApplicationController
     end
 
     def set_account
-      @account = family.accounts.find(params[:id])
+      @account = Current.user.accessible_accounts.find(params[:id])
+    end
+
+    def set_manageable_account
+      @account = Current.user.accessible_accounts.find(params[:id])
+      permission = @account.permission_for(Current.user)
+      unless permission.in?([ :owner, :full_control ])
+        respond_to do |format|
+          format.html { redirect_to account_path(@account), alert: t("accounts.not_authorized") }
+          format.turbo_stream { stream_redirect_to(account_path(@account), alert: t("accounts.not_authorized")) }
+        end
+        nil
+      end
     end
 
     # Builds sync stats maps for all provider types to avoid N+1 queries in views
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 310abfcd0..79c92d76c 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -81,4 +81,14 @@ class ApplicationController < ActionController::Base
     def show_demo_warning?
       demo_host_match?
     end
+
+    def accessible_accounts
+      Current.accessible_accounts
+    end
+    helper_method :accessible_accounts
+
+    def finance_accounts
+      Current.finance_accounts
+    end
+    helper_method :finance_accounts
 end
diff --git a/app/controllers/concerns/accountable_resource.rb b/app/controllers/concerns/accountable_resource.rb
index 003d61edc..fcf51dbe9 100644
--- a/app/controllers/concerns/accountable_resource.rb
+++ b/app/controllers/concerns/accountable_resource.rb
@@ -2,9 +2,10 @@ module AccountableResource
   extend ActiveSupport::Concern
 
   included do
-    include Periodable
+    include Periodable, StreamExtensions
 
-    before_action :set_account, only: [ :show, :edit, :update ]
+    before_action :set_account, only: [ :show ]
+    before_action :set_manageable_account, only: [ :edit, :update ]
     before_action :set_link_options, only: :new
   end
 
@@ -39,11 +40,14 @@ module AccountableResource
     rescue Date::Error
       nil
     end || (Time.zone.today - 2.years)
-    @account = Current.family.accounts.create_and_sync(
-      account_params.except(:return_to, :opening_balance_date),
-      opening_balance_date: opening_balance_date
-    )
-    @account.lock_saved_attributes!
+    Account.transaction do
+      @account = Current.family.accounts.create_and_sync(
+        account_params.except(:return_to, :opening_balance_date).merge(owner: Current.user),
+        opening_balance_date: opening_balance_date
+      )
+      @account.lock_saved_attributes!
+      @account.auto_share_with_family! if Current.family.share_all_by_default?
+    end
 
     redirect_to account_params[:return_to].presence || @account, notice: t("accounts.create.success", type: accountable_type.name.underscore.humanize)
   end
@@ -87,7 +91,19 @@ module AccountableResource
     end
 
     def set_account
-      @account = Current.family.accounts.find(params[:id])
+      @account = Current.user.accessible_accounts.find(params[:id])
+    end
+
+    def set_manageable_account
+      @account = Current.user.accessible_accounts.find(params[:id])
+      permission = @account.permission_for(Current.user)
+      unless permission.in?([ :owner, :full_control ])
+        respond_to do |format|
+          format.html { redirect_to account_path(@account), alert: t("accounts.not_authorized") }
+          format.turbo_stream { stream_redirect_to(account_path(@account), alert: t("accounts.not_authorized")) }
+        end
+        nil
+      end
     end
 
     def account_params
diff --git a/app/controllers/concerns/entryable_resource.rb b/app/controllers/concerns/entryable_resource.rb
index 443b04832..11b34d83b 100644
--- a/app/controllers/concerns/entryable_resource.rb
+++ b/app/controllers/concerns/entryable_resource.rb
@@ -5,13 +5,15 @@ module EntryableResource
     include StreamExtensions, ActionView::RecordIdentifier
 
     before_action :set_entry, only: %i[show update destroy]
+
+    helper_method :can_edit_entry?, :can_annotate_entry?
   end
 
   def show
   end
 
   def new
-    account = Current.family.accounts.find_by(id: params[:account_id])
+    account = accessible_accounts.find_by(id: params[:account_id])
 
     @entry = Current.family.entries.new(
       account: account,
@@ -29,11 +31,18 @@ module EntryableResource
   end
 
   def destroy
-    account = @entry.account
+    unless can_edit_entry?
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @entry.destroy!
     @entry.sync_account_later
 
-    redirect_back_or_to account_path(account), notice: t("account.entries.destroy.success")
+    redirect_back_or_to account_path(@entry.account), notice: t("account.entries.destroy.success")
   end
 
   private
@@ -42,6 +51,21 @@ module EntryableResource
     end
 
     def set_entry
-      @entry = Current.family.entries.find(params[:id])
+      @entry = Current.family.entries
+                 .joins(:account)
+                 .merge(Account.accessible_by(Current.user))
+                 .find(params[:id])
+    end
+
+    def entry_permission
+      @entry_permission ||= @entry&.account&.permission_for(Current.user)
+    end
+
+    def can_edit_entry?
+      entry_permission.in?([ :owner, :full_control ])
+    end
+
+    def can_annotate_entry?
+      entry_permission.in?([ :owner, :full_control, :read_write ])
     end
 end
diff --git a/app/controllers/holdings_controller.rb b/app/controllers/holdings_controller.rb
index 24f7c9726..98e30a03c 100644
--- a/app/controllers/holdings_controller.rb
+++ b/app/controllers/holdings_controller.rb
@@ -1,8 +1,11 @@
 class HoldingsController < ApplicationController
+  include StreamExtensions
+
   before_action :set_holding, only: %i[show update destroy unlock_cost_basis remap_security reset_security sync_prices]
+  before_action :require_holding_write_permission!, only: %i[update destroy unlock_cost_basis remap_security reset_security]
 
   def index
-    @account = Current.family.accounts.find(params[:account_id])
+    @account = accessible_accounts.find(params[:account_id])
   end
 
   def show
@@ -137,7 +140,20 @@ class HoldingsController < ApplicationController
 
   private
     def set_holding
-      @holding = Current.family.holdings.find(params[:id])
+      @holding = Current.family.holdings
+                   .joins(:account)
+                   .merge(Account.accessible_by(Current.user))
+                   .find(params[:id])
+    end
+
+    def require_holding_write_permission!
+      permission = @holding.account.permission_for(Current.user)
+      unless permission.in?([ :owner, :full_control ])
+        respond_to do |format|
+          format.html { redirect_back_or_to account_path(@holding.account), alert: t("accounts.not_authorized") }
+          format.turbo_stream { stream_redirect_back_or_to(account_path(@holding.account), alert: t("accounts.not_authorized")) }
+        end
+      end
     end
 
     def holding_params
diff --git a/app/controllers/import/uploads_controller.rb b/app/controllers/import/uploads_controller.rb
index 3d8d44732..3cf58ffda 100644
--- a/app/controllers/import/uploads_controller.rb
+++ b/app/controllers/import/uploads_controller.rb
@@ -19,7 +19,7 @@ class Import::UploadsController < ApplicationController
     elsif @import.is_a?(SureImport)
       update_sure_import_upload
     elsif csv_valid?(csv_str)
-      @import.account = Current.family.accounts.find_by(id: import_account_id)
+      @import.account = accessible_accounts.find_by(id: import_account_id)
       @import.assign_attributes(raw_file_str: csv_str, col_sep: upload_params[:col_sep])
       @import.save!(validate: false)
 
@@ -78,7 +78,7 @@ class Import::UploadsController < ApplicationController
       end
 
       ActiveRecord::Base.transaction do
-        @import.account = Current.family.accounts.find(import_account_id)
+        @import.account = accessible_accounts.find(import_account_id)
         @import.raw_file_str = QifParser.normalize_encoding(csv_str)
         @import.save!(validate: false)
         @import.generate_rows_from_csv
diff --git a/app/controllers/imports_controller.rb b/app/controllers/imports_controller.rb
index d8f581c1b..4a3cc0492 100644
--- a/app/controllers/imports_controller.rb
+++ b/app/controllers/imports_controller.rb
@@ -8,7 +8,7 @@ class ImportsController < ApplicationController
     account_id = params.dig(:pdf_import, :account_id) || params.dig(:import, :account_id)
 
     if account_id.present?
-      account = Current.family.accounts.find_by(id: account_id)
+      account = accessible_accounts.find_by(id: account_id)
       unless account
         redirect_back_or_to import_path(@import), alert: t("imports.update.invalid_account", default: "Account not found.")
         return
@@ -67,7 +67,7 @@ class ImportsController < ApplicationController
     type = params.dig(:import, :type).to_s
     type = "TransactionImport" unless Import::TYPES.include?(type)
 
-    account = Current.family.accounts.find_by(id: params.dig(:import, :account_id))
+    account = accessible_accounts.find_by(id: params.dig(:import, :account_id))
     import = Current.family.imports.create!(
       type: type,
       account: account,
diff --git a/app/controllers/pages_controller.rb b/app/controllers/pages_controller.rb
index 29a00cdf8..e0802c1c5 100644
--- a/app/controllers/pages_controller.rb
+++ b/app/controllers/pages_controller.rb
@@ -11,7 +11,7 @@ class PagesController < ApplicationController
 
     @balance_sheet = Current.family.balance_sheet
     @investment_statement = Current.family.investment_statement
-    @accounts = Current.family.accounts.visible.with_attached_logo
+    @accounts = Current.user.accessible_accounts.visible.with_attached_logo
 
     family_currency = Current.family.currency
 
@@ -90,7 +90,7 @@ class PagesController < ApplicationController
           title: "pages.dashboard.cashflow_sankey.title",
           partial: "pages/dashboard/cashflow_sankey",
           locals: { sankey_data: @cashflow_sankey_data, period: @period },
-          visible: Current.family.accounts.any?,
+          visible: @accounts.any?,
           collapsible: true
         },
         {
@@ -98,7 +98,7 @@ class PagesController < ApplicationController
           title: "pages.dashboard.outflows_donut.title",
           partial: "pages/dashboard/outflows_donut",
           locals: { outflows_data: @outflows_data, period: @period },
-          visible: Current.family.accounts.any? && @outflows_data[:categories].present?,
+          visible: @accounts.any? && @outflows_data[:categories].present?,
           collapsible: true
         },
         {
@@ -106,7 +106,7 @@ class PagesController < ApplicationController
           title: "pages.dashboard.investment_summary.title",
           partial: "pages/dashboard/investment_summary",
           locals: { investment_statement: @investment_statement, period: @period },
-          visible: Current.family.accounts.any? && @investment_statement.investment_accounts.any?,
+          visible: @accounts.any? && @investment_statement.investment_accounts.any?,
           collapsible: true
         },
         {
@@ -114,7 +114,7 @@ class PagesController < ApplicationController
           title: "pages.dashboard.net_worth_chart.title",
           partial: "pages/dashboard/net_worth_chart",
           locals: { balance_sheet: @balance_sheet, period: @period },
-          visible: Current.family.accounts.any?,
+          visible: @accounts.any?,
           collapsible: true
         },
         {
@@ -122,7 +122,7 @@ class PagesController < ApplicationController
           title: "pages.dashboard.balance_sheet.title",
           partial: "pages/dashboard/balance_sheet",
           locals: { balance_sheet: @balance_sheet },
-          visible: Current.family.accounts.any?,
+          visible: @accounts.any?,
           collapsible: true
         }
       ]
diff --git a/app/controllers/pending_duplicate_merges_controller.rb b/app/controllers/pending_duplicate_merges_controller.rb
index 460f9894e..3e1d68786 100644
--- a/app/controllers/pending_duplicate_merges_controller.rb
+++ b/app/controllers/pending_duplicate_merges_controller.rb
@@ -17,6 +17,12 @@ class PendingDuplicateMergesController < ApplicationController
   end
 
   def create
+    permission = @transaction.entry.account.permission_for(Current.user)
+    unless permission.in?([ :owner, :full_control ])
+      redirect_back_or_to transactions_path, alert: t("accounts.not_authorized")
+      return
+    end
+
     # Manually merge the pending transaction with the selected posted transaction
     unless merge_params[:posted_entry_id].present?
       redirect_back_or_to transactions_path, alert: "Please select a posted transaction to merge with"
@@ -54,7 +60,7 @@ class PendingDuplicateMergesController < ApplicationController
 
   private
     def set_transaction
-      entry = Current.family.entries.find(params[:transaction_id])
+      entry = Current.accessible_entries.find(params[:transaction_id])
       @transaction = entry.entryable
 
       unless @transaction.is_a?(Transaction) && @transaction.pending?
diff --git a/app/controllers/properties_controller.rb b/app/controllers/properties_controller.rb
index c222d5a74..563738efb 100644
--- a/app/controllers/properties_controller.rb
+++ b/app/controllers/properties_controller.rb
@@ -2,6 +2,7 @@ class PropertiesController < ApplicationController
   include AccountableResource, StreamExtensions
 
   before_action :set_property, only: [ :balances, :address, :update_balances, :update_address ]
+  before_action :require_property_write_permission!, only: [ :update_balances, :update_address ]
 
   def new
     @account = Current.family.accounts.build(accountable: Property.new)
@@ -9,8 +10,9 @@ class PropertiesController < ApplicationController
 
   def create
     @account = Current.family.accounts.create!(
-      property_params.merge(currency: Current.family.currency, balance: 0, status: "draft")
+      property_params.merge(currency: Current.family.currency, balance: 0, status: "draft", owner: Current.user)
     )
+    @account.auto_share_with_family! if Current.family.share_all_by_default?
 
     redirect_to balances_property_path(@account)
   end
@@ -100,7 +102,17 @@ class PropertiesController < ApplicationController
     end
 
     def set_property
-      @account = Current.family.accounts.find(params[:id])
+      @account = accessible_accounts.find(params[:id])
       @property = @account.property
     end
+
+    def require_property_write_permission!
+      permission = @account.permission_for(Current.user)
+      unless permission.in?([ :owner, :full_control ])
+        respond_to do |format|
+          format.html { redirect_back_or_to account_path(@account), alert: t("accounts.not_authorized") }
+          format.turbo_stream { stream_redirect_back_or_to(account_path(@account), alert: t("accounts.not_authorized")) }
+        end
+      end
+    end
 end
diff --git a/app/controllers/reports_controller.rb b/app/controllers/reports_controller.rb
index d76a82c12..83c9b0f76 100644
--- a/app/controllers/reports_controller.rb
+++ b/app/controllers/reports_controller.rb
@@ -124,10 +124,10 @@ class ReportsController < ApplicationController
       @investment_metrics = build_investment_metrics
 
       # Investment flows (contributions/withdrawals)
-      @investment_flows = InvestmentFlowStatement.new(Current.family).period_totals(period: @period)
+      @investment_flows = InvestmentFlowStatement.new(Current.family, user: Current.user).period_totals(period: @period)
 
       # Flags for view rendering
-      @has_accounts = Current.family.accounts.any?
+      @has_accounts = accessible_accounts.any?
     end
 
     def preferences_params
@@ -145,7 +145,7 @@ class ReportsController < ApplicationController
           title: "reports.net_worth.title",
           partial: "reports/net_worth",
           locals: { net_worth_metrics: @net_worth_metrics },
-          visible: Current.family.accounts.any?,
+          visible: accessible_accounts.any?,
           collapsible: true
         },
         {
@@ -153,7 +153,7 @@ class ReportsController < ApplicationController
           title: "reports.trends.title",
           partial: "reports/trends_insights",
           locals: { trends_data: @trends_data },
-          visible: Current.family.transactions.any?,
+          visible: @has_accounts,
           collapsible: true
         },
         {
@@ -182,7 +182,7 @@ class ReportsController < ApplicationController
             start_date: @start_date,
             end_date: @end_date
           },
-          visible: Current.family.transactions.any?,
+          visible: @has_accounts,
           collapsible: true
         }
       ]
@@ -353,7 +353,7 @@ class ReportsController < ApplicationController
         .where.not(kind: Transaction::BUDGET_EXCLUDED_KINDS)
         .includes(entry: :account, category: :parent)
 
-      # Apply filters
+      # Apply filters (includes finance account scoping)
       transactions = apply_transaction_filters(transactions)
 
       # Get trades in the period (matching income_statement logic)
@@ -364,6 +364,8 @@ class ReportsController < ApplicationController
         .where(entries: { entryable_type: "Trade", excluded: false, date: @period.date_range })
         .includes(entry: :account, category: :parent)
 
+      trades = apply_entry_filters(trades)
+
       # Get sort parameters
       sort_by = params[:sort_by] || "amount"
       sort_direction = params[:sort_direction] || "desc"
@@ -558,49 +560,60 @@ class ReportsController < ApplicationController
       }
     end
 
-    def apply_transaction_filters(transactions)
+    def apply_transaction_filters(scope)
+      scope = apply_entry_filters(scope)
+
+      # Filter by tag (Transaction-specific — trades don't have taggings)
+      if params[:filter_tag_id].present?
+        scope = scope.joins(:taggings).where(taggings: { tag_id: params[:filter_tag_id] })
+      end
+
+      scope
+    end
+
+    # Filters applicable to both transactions and trades (entry-level + category)
+    def apply_entry_filters(scope)
+      # Scope to user's finance accounts
+      finance_account_ids = Current.user&.finance_accounts&.pluck(:id) || []
+      scope = scope.where(entries: { account_id: finance_account_ids })
+
       # Filter by category (including subcategories)
       if params[:filter_category_id].present?
         category_id = params[:filter_category_id]
         # Scope to family's categories to prevent cross-family data access
         subcategory_ids = Current.family.categories.where(parent_id: category_id).pluck(:id)
         all_category_ids = [ category_id ] + subcategory_ids
-        transactions = transactions.where(category_id: all_category_ids)
+        scope = scope.where(category_id: all_category_ids)
       end
 
       # Filter by account
       if params[:filter_account_id].present?
-        transactions = transactions.where(entries: { account_id: params[:filter_account_id] })
-      end
-
-      # Filter by tag
-      if params[:filter_tag_id].present?
-        transactions = transactions.joins(:taggings).where(taggings: { tag_id: params[:filter_tag_id] })
+        scope = scope.where(entries: { account_id: params[:filter_account_id] })
       end
 
       # Filter by amount range
       if params[:filter_amount_min].present?
-        transactions = transactions.where("ABS(entries.amount) >= ?", params[:filter_amount_min].to_f)
+        scope = scope.where("ABS(entries.amount) >= ?", params[:filter_amount_min].to_f)
       end
 
       if params[:filter_amount_max].present?
-        transactions = transactions.where("ABS(entries.amount) <= ?", params[:filter_amount_max].to_f)
+        scope = scope.where("ABS(entries.amount) <= ?", params[:filter_amount_max].to_f)
       end
 
       # Filter by date range (within the period)
       if params[:filter_date_start].present?
         filter_start = Date.parse(params[:filter_date_start])
-        transactions = transactions.where("entries.date >= ?", filter_start) if filter_start >= @start_date
+        scope = scope.where("entries.date >= ?", filter_start) if filter_start >= @start_date
       end
 
       if params[:filter_date_end].present?
         filter_end = Date.parse(params[:filter_date_end])
-        transactions = transactions.where("entries.date <= ?", filter_end) if filter_end <= @end_date
+        scope = scope.where("entries.date <= ?", filter_end) if filter_end <= @end_date
       end
 
-      transactions
+      scope
     rescue Date::Error
-      transactions
+      scope
     end
 
     def build_transactions_breakdown_for_export
diff --git a/app/controllers/splits_controller.rb b/app/controllers/splits_controller.rb
index 3fab45a1b..c7b264af5 100644
--- a/app/controllers/splits_controller.rb
+++ b/app/controllers/splits_controller.rb
@@ -1,5 +1,6 @@
 class SplitsController < ApplicationController
   before_action :set_entry
+  before_action :require_split_write_permission!, only: %i[create update destroy]
 
   def new
     @categories = Current.family.categories.alphabetically
@@ -82,7 +83,14 @@ class SplitsController < ApplicationController
   private
 
     def set_entry
-      @entry = Current.family.entries.find(params[:transaction_id])
+      @entry = Current.accessible_entries.find(params[:transaction_id])
+    end
+
+    def require_split_write_permission!
+      permission = @entry.account.permission_for(Current.user)
+      unless permission.in?([ :owner, :full_control ])
+        redirect_back_or_to transactions_path, alert: t("accounts.not_authorized")
+      end
     end
 
     def resolve_to_parent!
diff --git a/app/controllers/trades_controller.rb b/app/controllers/trades_controller.rb
index e3061a719..8dc280e70 100644
--- a/app/controllers/trades_controller.rb
+++ b/app/controllers/trades_controller.rb
@@ -5,7 +5,7 @@ class TradesController < ApplicationController
 
   # Defaults to a buy trade
   def new
-    @account = Current.family.accounts.find_by(id: params[:account_id])
+    @account = accessible_accounts.find_by(id: params[:account_id])
     @model = Current.family.entries.new(
       account: @account,
       currency: @account ? @account.currency : Current.family.currency,
@@ -15,7 +15,16 @@ class TradesController < ApplicationController
 
   # Can create a trade, transaction (e.g. "fees"), or transfer (e.g. "withdrawal")
   def create
-    @account = Current.family.accounts.find(params[:account_id])
+    @account = accessible_accounts.find(params[:account_id])
+
+    unless @account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @model = Trade::CreateForm.new(create_params.merge(account: @account)).create
 
     if @model.persisted?
@@ -37,6 +46,14 @@ class TradesController < ApplicationController
   end
 
   def update
+    unless can_edit_entry?
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     if @entry.update(update_entry_params)
       @entry.lock_saved_attributes!
       @entry.mark_user_modified!
@@ -69,6 +86,14 @@ class TradesController < ApplicationController
   end
 
   def unlock
+    unless @entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @entry.unlock_for_sync!
     flash[:notice] = t("entries.unlock.success")
 
@@ -77,7 +102,10 @@ class TradesController < ApplicationController
 
   private
     def set_entry_for_unlock
-      trade = Current.family.trades.find(params[:id])
+      trade = Current.family.trades
+                .joins(entry: :account)
+                .merge(Account.accessible_by(Current.user))
+                .find(params[:id])
       @entry = trade.entry
     end
 
diff --git a/app/controllers/transaction_attachments_controller.rb b/app/controllers/transaction_attachments_controller.rb
index 6aa39bffd..2a9ff5567 100644
--- a/app/controllers/transaction_attachments_controller.rb
+++ b/app/controllers/transaction_attachments_controller.rb
@@ -1,6 +1,7 @@
 class TransactionAttachmentsController < ApplicationController
   before_action :set_transaction
   before_action :set_attachment, only: [ :show, :destroy ]
+  before_action :set_permissions, only: [ :create, :destroy ]
 
   def show
     disposition = params[:disposition] == "attachment" ? "attachment" : "inline"
@@ -8,6 +9,11 @@ class TransactionAttachmentsController < ApplicationController
   end
 
   def create
+    unless @can_upload
+      redirect_back_or_to transaction_path(@transaction), alert: t("accounts.not_authorized")
+      return
+    end
+
     attachments = attachment_params
 
     if attachments.present?
@@ -60,6 +66,11 @@ class TransactionAttachmentsController < ApplicationController
   end
 
   def destroy
+    unless @can_delete
+      redirect_back_or_to transaction_path(@transaction), alert: t("accounts.not_authorized")
+      return
+    end
+
     @attachment.purge
     message = t("transactions.attachments.attachment_deleted")
     respond_to do |format|
@@ -77,13 +88,22 @@ class TransactionAttachmentsController < ApplicationController
   private
 
     def set_transaction
-      @transaction = Current.family.transactions.find(params[:transaction_id])
+      @transaction = Current.family.transactions
+                       .joins(entry: :account)
+                       .merge(Account.accessible_by(Current.user))
+                       .find(params[:transaction_id])
     end
 
     def set_attachment
       @attachment = @transaction.attachments.find(params[:id])
     end
 
+    def set_permissions
+      permission = @transaction.entry.account.permission_for(Current.user)
+      @can_upload = permission.in?([ :owner, :full_control, :read_write ])
+      @can_delete = permission.in?([ :owner, :full_control ])
+    end
+
     def attachment_params
       if params.has_key?(:attachments)
         Array(params.fetch(:attachments, [])).reject(&:blank?).map do |param|
diff --git a/app/controllers/transaction_categories_controller.rb b/app/controllers/transaction_categories_controller.rb
index d8fc64e96..1acffed57 100644
--- a/app/controllers/transaction_categories_controller.rb
+++ b/app/controllers/transaction_categories_controller.rb
@@ -2,7 +2,14 @@ class TransactionCategoriesController < ApplicationController
   include ActionView::RecordIdentifier
 
   def update
-    @entry = Current.family.entries.transactions.find(params[:transaction_id])
+    @entry = Current.accessible_entries.transactions.find(params[:transaction_id])
+
+    permission = @entry.account.permission_for(Current.user)
+    unless permission.in?([ :owner, :full_control, :read_write ])
+      redirect_back_or_to transaction_path(@entry), alert: t("accounts.not_authorized")
+      return
+    end
+
     @entry.update!(entry_params)
 
     transaction = @entry.transaction
diff --git a/app/controllers/transactions/bulk_deletions_controller.rb b/app/controllers/transactions/bulk_deletions_controller.rb
index 99951d26d..37a85ed88 100644
--- a/app/controllers/transactions/bulk_deletions_controller.rb
+++ b/app/controllers/transactions/bulk_deletions_controller.rb
@@ -1,7 +1,11 @@
 class Transactions::BulkDeletionsController < ApplicationController
   def create
     # Exclude split children from bulk delete - they must be deleted via unsplit on parent
-    entries_scope = Current.family.entries.where(parent_entry_id: nil)
+    # Only allow deletion from accounts where user has owner or full_control permission
+    writable_account_ids = writable_accounts.pluck(:id)
+    entries_scope = Current.family.entries
+                      .where(account_id: writable_account_ids)
+                      .where(parent_entry_id: nil)
     destroyed = entries_scope.destroy_by(id: bulk_delete_params[:entry_ids])
     destroyed.map(&:account).uniq.each(&:sync_later)
     redirect_back_or_to transactions_url, notice: "#{destroyed.count} transaction#{destroyed.count == 1 ? "" : "s"} deleted"
@@ -11,4 +15,16 @@ class Transactions::BulkDeletionsController < ApplicationController
     def bulk_delete_params
       params.require(:bulk_delete).permit(entry_ids: [])
     end
+
+    # Accounts where the user can delete entries (owner or full_control)
+    def writable_accounts
+      Current.family.accounts
+        .left_joins(:account_shares)
+        .where(
+          "accounts.owner_id = :uid OR (account_shares.user_id = :uid AND account_shares.permission = :perm)",
+          uid: Current.user.id,
+          perm: "full_control"
+        )
+        .distinct
+    end
 end
diff --git a/app/controllers/transactions_controller.rb b/app/controllers/transactions_controller.rb
index 096c313e5..43c4c9ff0 100644
--- a/app/controllers/transactions_controller.rb
+++ b/app/controllers/transactions_controller.rb
@@ -15,7 +15,8 @@ class TransactionsController < ApplicationController
 
   def index
     @q = search_params
-    @search = Transaction::Search.new(Current.family, filters: @q)
+    accessible_account_ids = Current.user.accessible_accounts.pluck(:id)
+    @search = Transaction::Search.new(Current.family, filters: @q, accessible_account_ids: accessible_account_ids)
 
     base_scope = @search.transactions_scope
                        .reverse_chronological
@@ -90,7 +91,16 @@ class TransactionsController < ApplicationController
   end
 
   def create
-    account = Current.family.accounts.find(params.dig(:entry, :account_id))
+    account = Current.user.accessible_accounts.find(params.dig(:entry, :account_id))
+
+    unless account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @entry = account.entries.new(entry_params)
 
     if @entry.save
@@ -111,7 +121,7 @@ class TransactionsController < ApplicationController
   end
 
   def update
-    if @entry.update(entry_params)
+    if @entry.update(permitted_entry_params)
       transaction = @entry.transaction
 
       if needs_rule_notification?(transaction)
@@ -155,7 +165,15 @@ class TransactionsController < ApplicationController
   end
 
   def merge_duplicate
-    transaction = Current.family.transactions.includes(entry: :account).find(params[:id])
+    transaction = accessible_transactions.includes(entry: :account).find(params[:id])
+
+    unless transaction.entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(transaction.entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(transaction.entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
 
     if transaction.merge_with_duplicate!
       flash[:notice] = t("transactions.merge_duplicate.success")
@@ -171,7 +189,15 @@ class TransactionsController < ApplicationController
   end
 
   def dismiss_duplicate
-    transaction = Current.family.transactions.includes(entry: :account).find(params[:id])
+    transaction = accessible_transactions.includes(entry: :account).find(params[:id])
+
+    unless transaction.entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(transaction.entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(transaction.entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
 
     if transaction.dismiss_duplicate_suggestion!
       flash[:notice] = t("transactions.dismiss_duplicate.success")
@@ -187,9 +213,17 @@ class TransactionsController < ApplicationController
   end
 
   def convert_to_trade
-    @transaction = Current.family.transactions.includes(entry: :account).find(params[:id])
+    @transaction = accessible_transactions.includes(entry: :account).find(params[:id])
     @entry = @transaction.entry
 
+    unless @entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     unless @entry.account.investment?
       flash[:alert] = t("transactions.convert_to_trade.errors.not_investment_account")
       redirect_back_or_to transactions_path
@@ -200,9 +234,17 @@ class TransactionsController < ApplicationController
   end
 
   def create_trade_from_transaction
-    @transaction = Current.family.transactions.includes(entry: :account).find(params[:id])
+    @transaction = accessible_transactions.includes(entry: :account).find(params[:id])
     @entry = @transaction.entry
 
+    unless @entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     # Pre-transaction validations
     unless @entry.account.investment?
       flash[:alert] = t("transactions.convert_to_trade.errors.not_investment_account")
@@ -277,6 +319,14 @@ class TransactionsController < ApplicationController
   end
 
   def unlock
+    unless @entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @entry.unlock_for_sync!
     flash[:notice] = t("entries.unlock.success")
 
@@ -284,7 +334,15 @@ class TransactionsController < ApplicationController
   end
 
   def mark_as_recurring
-    transaction = Current.family.transactions.includes(entry: :account).find(params[:id])
+    transaction = accessible_transactions.includes(entry: :account).find(params[:id])
+
+    unless transaction.entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(transaction.entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(transaction.entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
 
     # Check if a recurring transaction already exists for this pattern
     existing = Current.family.recurring_transactions.find_by(
@@ -334,10 +392,16 @@ class TransactionsController < ApplicationController
   end
 
   private
+    def accessible_transactions
+      Current.family.transactions
+        .joins(entry: :account)
+        .merge(Account.accessible_by(Current.user))
+    end
+
     def duplicate_source
       return @duplicate_source if defined?(@duplicate_source)
       @duplicate_source = if params[:duplicate_entry_id].present?
-        source = Current.family.entries.find_by(id: params[:duplicate_entry_id])
+        source = Current.family.entries.joins(:account).merge(Account.accessible_by(Current.user)).find_by(id: params[:duplicate_entry_id])
         source if source&.transaction?
       end
     end
@@ -364,7 +428,7 @@ class TransactionsController < ApplicationController
     end
 
     def set_entry_for_unlock
-      transaction = Current.family.transactions.find(params[:id])
+      transaction = accessible_transactions.find(params[:id])
       @entry = transaction.entry
     end
 
@@ -398,6 +462,25 @@ class TransactionsController < ApplicationController
       entry_params
     end
 
+    # Filters entry_params based on the user's permission on the account.
+    # read_write users can only annotate (category, tags, notes, merchant).
+    # read_only users cannot update anything.
+    def permitted_entry_params
+      case entry_permission
+      when :owner, :full_control
+        entry_params
+      when :read_write
+        # Annotate only: category, tags, merchant, notes
+        ep = entry_params.slice(:notes)
+        if entry_params[:entryable_attributes].present?
+          ep[:entryable_attributes] = entry_params[:entryable_attributes].slice(:id, :category_id, :merchant_id, :tag_ids)
+        end
+        ep
+      else
+        {} # read_only — no edits allowed
+      end
+    end
+
     def search_params
       cleaned_params = params.fetch(:q, {})
               .permit(
diff --git a/app/controllers/transfer_matches_controller.rb b/app/controllers/transfer_matches_controller.rb
index ea9425039..5792db0be 100644
--- a/app/controllers/transfer_matches_controller.rb
+++ b/app/controllers/transfer_matches_controller.rb
@@ -2,11 +2,17 @@ class TransferMatchesController < ApplicationController
   before_action :set_entry
 
   def new
-    @accounts = Current.family.accounts.visible.alphabetically.where.not(id: @entry.account_id)
+    @accounts = accessible_accounts.visible.alphabetically.where.not(id: @entry.account_id)
     @transfer_match_candidates = @entry.transaction.transfer_match_candidates
   end
 
   def create
+    permission = @entry.account.permission_for(Current.user)
+    unless permission.in?([ :owner, :full_control ])
+      redirect_back_or_to transactions_path, alert: t("accounts.not_authorized")
+      return
+    end
+
     @transfer = build_transfer
     Transfer.transaction do
       @transfer.save!
@@ -32,7 +38,7 @@ class TransferMatchesController < ApplicationController
 
   private
     def set_entry
-      @entry = Current.family.entries.find(params[:transaction_id])
+      @entry = Current.accessible_entries.find(params[:transaction_id])
     end
 
     def transfer_match_params
@@ -41,7 +47,7 @@ class TransferMatchesController < ApplicationController
 
     def build_transfer
       if transfer_match_params[:method] == "new"
-        target_account = Current.family.accounts.find(transfer_match_params[:target_account_id])
+        target_account = accessible_accounts.find(transfer_match_params[:target_account_id])
 
         missing_transaction = Transaction.new(
           entry: target_account.entries.build(
@@ -60,7 +66,7 @@ class TransferMatchesController < ApplicationController
         transfer.status = "confirmed"
         transfer
       else
-        target_transaction = Current.family.entries.find(transfer_match_params[:matched_entry_id])
+        target_transaction = Current.accessible_entries.find(transfer_match_params[:matched_entry_id])
 
         transfer = Transfer.find_or_initialize_by(
           inflow_transaction: @entry.amount.negative? ? @entry.transaction : target_transaction.transaction,
diff --git a/app/controllers/transfers_controller.rb b/app/controllers/transfers_controller.rb
index 21d68bb78..b7c571d85 100644
--- a/app/controllers/transfers_controller.rb
+++ b/app/controllers/transfers_controller.rb
@@ -7,7 +7,7 @@ class TransfersController < ApplicationController
     @transfer = Transfer.new
     @from_account_id = params[:from_account_id]
 
-    @accounts = Current.family.accounts
+    @accounts = accessible_accounts
     .alphabetically
     .includes(
       :account_providers,
@@ -20,10 +20,23 @@ class TransfersController < ApplicationController
   end
 
   def create
+    # Validate user has write access to both accounts
+    source_account = accessible_accounts.find(transfer_params[:from_account_id])
+    destination_account = accessible_accounts.find(transfer_params[:to_account_id])
+
+    unless source_account.permission_for(Current.user).in?([ :owner, :full_control ]) &&
+           destination_account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to transactions_path, alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(transactions_path, alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @transfer = Transfer::Creator.new(
       family: Current.family,
-      source_account_id: transfer_params[:from_account_id],
-      destination_account_id: transfer_params[:to_account_id],
+      source_account_id: source_account.id,
+      destination_account_id: destination_account.id,
       date: Date.parse(transfer_params[:date]),
       amount: transfer_params[:amount].to_d
     ).create
@@ -41,6 +54,16 @@ class TransfersController < ApplicationController
   end
 
   def update
+    outflow_account = @transfer.outflow_transaction.entry.account
+    permission = outflow_account.permission_for(Current.user)
+    unless permission.in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to transactions_url, alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(transactions_url, alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     Transfer.transaction do
       update_transfer_status
       update_transfer_details unless transfer_update_params[:status] == "rejected"
@@ -53,16 +76,32 @@ class TransfersController < ApplicationController
   end
 
   def destroy
+    # Require write permission on at least the outflow account
+    outflow_account = @transfer.outflow_transaction.entry.account
+    permission = outflow_account.permission_for(Current.user)
+    unless permission.in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to transactions_url, alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(transactions_url, alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @transfer.destroy!
     redirect_back_or_to transactions_url, notice: t(".success")
   end
 
   private
     def set_transfer
-      # Finds the transfer and ensures the family owns it
+      # Finds the transfer and ensures the user has access to it
+      accessible_transaction_ids = Current.family.transactions
+        .joins(entry: :account)
+        .merge(Account.accessible_by(Current.user))
+        .select(:id)
+
       @transfer = Transfer
                     .where(id: params[:id])
-                    .where(inflow_transaction_id: Current.family.transactions.select(:id))
+                    .where(inflow_transaction_id: accessible_transaction_ids)
                     .first!
     end
 
diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
index fd0c33f6e..937452e95 100644
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -12,7 +12,7 @@ class UsersController < ApplicationController
 
   def update
     @user = Current.user
-    return if moniker_change_requested? && !ensure_admin
+    return if admin_family_change_requested? && !ensure_admin
 
     if email_changed?
       if @user.initiate_email_change(user_params[:email])
@@ -109,7 +109,7 @@ class UsersController < ApplicationController
       params.require(:user).permit(
         :first_name, :last_name, :email, :profile_image, :redirect_to, :delete_profile_image, :onboarded_at,
         :show_sidebar, :default_period, :default_account_order, :show_ai_sidebar, :ai_enabled, :theme, :set_onboarding_preferences_at, :set_onboarding_goals_at, :locale,
-        family_attributes: [ :name, :currency, :country, :date_format, :timezone, :locale, :month_start_day, :moniker, :id ],
+        family_attributes: [ :name, :currency, :country, :date_format, :timezone, :locale, :month_start_day, :moniker, :default_account_sharing, :id ],
         goals: []
       )
     end
@@ -118,11 +118,14 @@ class UsersController < ApplicationController
       @user = Current.user
     end
 
-    def moniker_change_requested?
-      requested_moniker = params.dig(:user, :family_attributes, :moniker)
-      return false if requested_moniker.blank?
+    def admin_family_change_requested?
+      family_attrs = params.dig(:user, :family_attributes)
+      return false if family_attrs.blank?
 
-      requested_moniker != Current.family.moniker
+      moniker_changed = family_attrs[:moniker].present? && family_attrs[:moniker] != Current.family.moniker
+      sharing_changed = family_attrs[:default_account_sharing].present? && family_attrs[:default_account_sharing] != Current.family.default_account_sharing
+
+      moniker_changed || sharing_changed
     end
 
     def ensure_admin
diff --git a/app/controllers/valuations_controller.rb b/app/controllers/valuations_controller.rb
index 5234c0bea..e8c08736c 100644
--- a/app/controllers/valuations_controller.rb
+++ b/app/controllers/valuations_controller.rb
@@ -2,7 +2,16 @@ class ValuationsController < ApplicationController
   include EntryableResource, StreamExtensions
 
   def confirm_create
-    @account = Current.family.accounts.find(params.dig(:entry, :account_id))
+    @account = accessible_accounts.find(params.dig(:entry, :account_id))
+
+    unless @account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @entry = @account.entries.build(entry_params.merge(currency: @account.currency))
 
     @reconciliation_dry_run = @entry.account.create_reconciliation(
@@ -15,7 +24,16 @@ class ValuationsController < ApplicationController
   end
 
   def confirm_update
-    @entry = Current.family.entries.find(params[:id])
+    @entry = Current.accessible_entries.find(params[:id])
+
+    unless @entry.account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     @account = @entry.account
     @entry.assign_attributes(entry_params.merge(currency: @account.currency))
 
@@ -30,7 +48,15 @@ class ValuationsController < ApplicationController
   end
 
   def create
-    account = Current.family.accounts.find(params.dig(:entry, :account_id))
+    account = accessible_accounts.find(params.dig(:entry, :account_id))
+
+    unless account.permission_for(Current.user).in?([ :owner, :full_control ])
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
 
     result = account.create_reconciliation(
       balance: entry_params[:amount],
@@ -49,6 +75,14 @@ class ValuationsController < ApplicationController
   end
 
   def update
+    unless can_edit_entry?
+      respond_to do |format|
+        format.html { redirect_back_or_to account_path(@entry.account), alert: t("accounts.not_authorized") }
+        format.turbo_stream { stream_redirect_back_or_to(account_path(@entry.account), alert: t("accounts.not_authorized")) }
+      end
+      return
+    end
+
     # Notes updating is independent of reconciliation, just a simple CRUD operation
     @entry.update!(notes: entry_params[:notes]) if entry_params[:notes].present?
 
diff --git a/app/models/account.rb b/app/models/account.rb
index 45a4635e4..54e44b27b 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -1,11 +1,16 @@
 class Account < ApplicationRecord
   include AASM, Syncable, Monetizable, Chartable, Linkable, Enrichable, Anchorable, Reconcileable, TaxTreatable
 
+  before_validation :assign_default_owner, on: :create
+
   validates :name, :balance, :currency, presence: true
 
   belongs_to :family
+  belongs_to :owner, class_name: "User", optional: true
   belongs_to :import, optional: true
 
+  has_many :account_shares, dependent: :destroy
+  has_many :shared_users, through: :account_shares, source: :user
   has_many :import_mappings, as: :mappable, dependent: :destroy, class_name: "Import::Mapping"
   has_many :entries, dependent: :destroy
   has_many :transactions, through: :entries, source: :entryable, source_type: "Transaction"
@@ -36,6 +41,24 @@ class Account < ApplicationRecord
     manual.where.not(status: :pending_deletion)
   }
 
+  # All accounts a user can access (owned + shared with them)
+  scope :accessible_by, ->(user) {
+    left_joins(:account_shares)
+      .where("accounts.owner_id = :uid OR account_shares.user_id = :uid", uid: user.id)
+      .distinct
+  }
+
+  # Accounts that count in a user's financial calculations
+  scope :included_in_finances_for, ->(user) {
+    left_joins(:account_shares)
+      .where(
+        "accounts.owner_id = :uid OR " \
+        "(account_shares.user_id = :uid AND account_shares.include_in_finances = true)",
+        uid: user.id
+      )
+      .distinct
+  }
+
   has_one_attached :logo, dependent: :purge_later
 
   delegated_type :accountable, types: Accountable::TYPES, dependent: :destroy
@@ -138,8 +161,9 @@ class Account < ApplicationRecord
         end
       end
 
+      family = simplefin_account.simplefin_item.family
       attributes = {
-        family: simplefin_account.simplefin_item.family,
+        family: family,
         name: simplefin_account.name,
         balance: balance,
         cash_balance: cash_balance,
@@ -165,8 +189,9 @@ class Account < ApplicationRecord
 
       cash_balance = balance
 
+      family = enable_banking_account.enable_banking_item.family
       attributes = {
-        family: enable_banking_account.enable_banking_item.family,
+        family: family,
         name: enable_banking_account.name,
         balance: balance,
         cash_balance: cash_balance,
@@ -344,4 +369,50 @@ class Account < ApplicationRecord
       raise "Unknown account type: #{accountable_type}"
     end
   end
+
+  def owned_by?(user)
+    user.present? && owner_id == user.id
+  end
+
+  def shared_with?(user)
+    owned_by?(user) ||
+      if account_shares.loaded?
+        account_shares.any? { |s| s.user_id == user.id }
+      else
+        account_shares.exists?(user: user)
+      end
+  end
+
+  def shared?
+    account_shares.any?
+  end
+
+  def permission_for(user)
+    return :owner if owned_by?(user)
+    account_shares.find_by(user: user)&.permission&.to_sym
+  end
+
+  def share_with!(user, permission: "read_only", include_in_finances: true)
+    account_shares.create!(user: user, permission: permission, include_in_finances: include_in_finances)
+  end
+
+  def unshare_with!(user)
+    account_shares.where(user: user).destroy_all
+  end
+
+  def auto_share_with_family!
+    records = family.users.where.not(id: owner_id).pluck(:id).map do |user_id|
+      { account_id: id, user_id: user_id, permission: "read_write",
+        include_in_finances: true, created_at: Time.current, updated_at: Time.current }
+    end
+
+    AccountShare.insert_all(records, unique_by: %i[account_id user_id]) if records.any?
+  end
+
+  private
+
+    def assign_default_owner
+      return if owner.present?
+      self.owner = Current.user || family&.users&.find_by(role: %w[admin super_admin]) || family&.users&.order(:created_at)&.first
+    end
 end
diff --git a/app/models/account/sync_complete_event.rb b/app/models/account/sync_complete_event.rb
index d26b62f83..79e8ec16c 100644
--- a/app/models/account/sync_complete_event.rb
+++ b/app/models/account/sync_complete_event.rb
@@ -16,16 +16,6 @@ class Account::SyncCompleteEvent
       locals: { account: account }
     )
 
-    # Replace the groups this account belongs to in both desktop and mobile sidebars
-    sidebar_targets.each do |(tab, mobile_flag)|
-      account.broadcast_replace_to(
-        account.family,
-        target: account_group.dom_id(tab: tab, mobile: mobile_flag),
-        partial: "accounts/accountable_group",
-        locals: { account_group: account_group, open: true, all_tab: tab == :all, mobile: mobile_flag }
-      )
-    end
-
     # If this is a manual, unlinked account (i.e. not part of a Plaid Item),
     # trigger the family sync complete broadcast so net worth graph is updated
     unless account.linked?
@@ -35,29 +25,4 @@ class Account::SyncCompleteEvent
     # Refresh entire account page (only applies if currently viewing this account)
     account.broadcast_refresh
   end
-
-  private
-    # Returns an array of [tab, mobile?] tuples that should receive an update.
-    # We broadcast to both the classification-specific tab and the "all" tab,
-    # for desktop (mobile: false) and mobile (mobile: true) variants.
-    def sidebar_targets
-      return [] unless account_group.present?
-
-      [
-        [ account_group.classification.to_sym, false ],
-        [ :all, false ],
-        [ account_group.classification.to_sym, true ],
-        [ :all, true ]
-      ]
-    end
-
-    def account_group
-      family_balance_sheet.account_groups.find do |group|
-        group.accounts.any? { |a| a.id == account.id }
-      end
-    end
-
-    def family_balance_sheet
-      account.family.balance_sheet
-    end
 end
diff --git a/app/models/account_share.rb b/app/models/account_share.rb
new file mode 100644
index 000000000..8737df625
--- /dev/null
+++ b/app/models/account_share.rb
@@ -0,0 +1,47 @@
+class AccountShare < ApplicationRecord
+  belongs_to :account
+  belongs_to :user
+
+  PERMISSIONS = %w[full_control read_write read_only].freeze
+
+  validates :permission, inclusion: { in: PERMISSIONS }
+  validates :user_id, uniqueness: { scope: :account_id }
+  validate :cannot_share_with_owner
+  validate :user_in_same_family
+
+  scope :with_permission, ->(permission) { where(permission: permission) }
+
+  def full_control?
+    permission == "full_control"
+  end
+
+  def read_write?
+    permission == "read_write"
+  end
+
+  def read_only?
+    permission == "read_only"
+  end
+
+  def can_annotate?
+    full_control? || read_write?
+  end
+
+  def can_edit?
+    full_control?
+  end
+
+  private
+
+    def cannot_share_with_owner
+      if account && user && account.owner_id == user_id
+        errors.add(:user, "is already the owner of this account")
+      end
+    end
+
+    def user_in_same_family
+      if account && user && user.family_id != account.family_id
+        errors.add(:user, "must be in the same family")
+      end
+    end
+end
diff --git a/app/models/balance_sheet.rb b/app/models/balance_sheet.rb
index e8f5f8442..6dd2db3ac 100644
--- a/app/models/balance_sheet.rb
+++ b/app/models/balance_sheet.rb
@@ -3,10 +3,11 @@ class BalanceSheet
 
   monetize :net_worth
 
-  attr_reader :family
+  attr_reader :family, :user
 
-  def initialize(family)
+  def initialize(family, user: nil)
     @family = family
+    @user = user || Current.user
   end
 
   def assets
@@ -55,15 +56,15 @@ class BalanceSheet
     end
 
     def account_totals
-      @account_totals ||= AccountTotals.new(family, sync_status_monitor: sync_status_monitor)
+      @account_totals ||= AccountTotals.new(family, user: user, sync_status_monitor: sync_status_monitor)
     end
 
     def net_worth_series_builder
-      @net_worth_series_builder ||= NetWorthSeriesBuilder.new(family)
+      @net_worth_series_builder ||= NetWorthSeriesBuilder.new(family, user: user)
     end
 
     def sorted(accounts)
-      account_order = Current.user&.account_order
+      account_order = user&.account_order
       order_key = account_order&.key || "name_asc"
 
       case order_key
diff --git a/app/models/balance_sheet/account_totals.rb b/app/models/balance_sheet/account_totals.rb
index 2a1f63761..10f6f94ee 100644
--- a/app/models/balance_sheet/account_totals.rb
+++ b/app/models/balance_sheet/account_totals.rb
@@ -1,6 +1,7 @@
 class BalanceSheet::AccountTotals
-  def initialize(family, sync_status_monitor:)
+  def initialize(family, user: nil, sync_status_monitor:)
     @family = family
+    @user = user
     @sync_status_monitor = sync_status_monitor
   end
 
@@ -13,10 +14,11 @@ class BalanceSheet::AccountTotals
   end
 
   private
-    attr_reader :family, :sync_status_monitor
+    attr_reader :family, :user, :sync_status_monitor
 
-    AccountRow = Data.define(:account, :converted_balance, :is_syncing) do
+    AccountRow = Data.define(:account, :converted_balance, :is_syncing, :included_in_finances) do
       def syncing? = is_syncing
+      def included_in_finances? = included_in_finances
 
       # Allows Rails path helpers to generate URLs from the wrapper
       def to_param = account.to_param
@@ -24,7 +26,19 @@ class BalanceSheet::AccountTotals
     end
 
     def visible_accounts
-      @visible_accounts ||= family.accounts.visible.with_attached_logo
+      @visible_accounts ||= begin
+        scope = family.accounts.visible.with_attached_logo
+        scope = scope.accessible_by(user) if user
+        scope
+      end
+    end
+
+    def finance_account_ids
+      @finance_account_ids ||= if user
+        family.accounts.included_in_finances_for(user).pluck(:id).to_set
+      else
+        nil
+      end
     end
 
     # Wraps each account in an AccountRow with its converted balance and sync status.
@@ -33,15 +47,17 @@ class BalanceSheet::AccountTotals
         AccountRow.new(
           account: account,
           converted_balance: converted_balance_for(account),
-          is_syncing: sync_status_monitor.account_syncing?(account)
+          is_syncing: sync_status_monitor.account_syncing?(account),
+          included_in_finances: finance_account_ids.nil? || finance_account_ids.include?(account.id)
         )
       end
     end
 
     # Returns the cache key for storing visible account IDs, invalidated on data updates.
     def cache_key
+      shares_version = user ? AccountShare.where(user: user).maximum(:updated_at)&.to_i : nil
       family.build_cache_key(
-        "balance_sheet_account_ids",
+        [ "balance_sheet_account_ids", user&.id, shares_version ].compact.join("_"),
         invalidate_on_data_updates: true
       )
     end
diff --git a/app/models/balance_sheet/classification_group.rb b/app/models/balance_sheet/classification_group.rb
index 32e64214c..968d4b6c0 100644
--- a/app/models/balance_sheet/classification_group.rb
+++ b/app/models/balance_sheet/classification_group.rb
@@ -21,7 +21,7 @@ class BalanceSheet::ClassificationGroup
   end
 
   def total
-    accounts.sum(&:converted_balance)
+    accounts.select { |a| a.respond_to?(:included_in_finances?) ? a.included_in_finances? : true }.sum(&:converted_balance)
   end
 
   def syncing?
diff --git a/app/models/balance_sheet/net_worth_series_builder.rb b/app/models/balance_sheet/net_worth_series_builder.rb
index f3e61a995..7c29a6ece 100644
--- a/app/models/balance_sheet/net_worth_series_builder.rb
+++ b/app/models/balance_sheet/net_worth_series_builder.rb
@@ -1,6 +1,7 @@
 class BalanceSheet::NetWorthSeriesBuilder
-  def initialize(family)
+  def initialize(family, user: nil)
     @family = family
+    @user = user
   end
 
   def net_worth_series(period: Period.last_30_days)
@@ -17,15 +18,22 @@ class BalanceSheet::NetWorthSeriesBuilder
   end
 
   private
-    attr_reader :family
+    attr_reader :family, :user
 
     def visible_account_ids
-      @visible_account_ids ||= family.accounts.visible.with_attached_logo.pluck(:id)
+      @visible_account_ids ||= begin
+        scope = family.accounts.visible
+        scope = scope.included_in_finances_for(user) if user
+        scope.pluck(:id)
+      end
     end
 
     def cache_key(period)
+      shares_version = user ? AccountShare.where(user: user).maximum(:updated_at)&.to_i : nil
       key = [
         "balance_sheet_net_worth_series",
+        user&.id,
+        shares_version,
         period.start_date,
         period.end_date
       ].compact.join("_")
diff --git a/app/models/current.rb b/app/models/current.rb
index 86b9e97ac..612c2af76 100644
--- a/app/models/current.rb
+++ b/app/models/current.rb
@@ -16,4 +16,19 @@ class Current < ActiveSupport::CurrentAttributes
   def true_user
     session&.user
   end
+
+  def accessible_accounts
+    return family&.accounts unless user
+    user.accessible_accounts
+  end
+
+  def finance_accounts
+    return family&.accounts unless user
+    user.finance_accounts
+  end
+
+  def accessible_entries
+    return family&.entries unless user
+    family.entries.joins(:account).merge(Account.accessible_by(user))
+  end
 end
diff --git a/app/models/family.rb b/app/models/family.rb
index a43b118a2..0ba8dc8b2 100644
--- a/app/models/family.rb
+++ b/app/models/family.rb
@@ -20,6 +20,7 @@ class Family < ApplicationRecord
 
   MONIKERS = [ "Family", "Group" ].freeze
   ASSISTANT_TYPES = %w[builtin external].freeze
+  SHARING_DEFAULTS = %w[shared private].freeze
 
   has_many :users, dependent: :destroy
   has_many :accounts, dependent: :destroy
@@ -49,6 +50,7 @@ class Family < ApplicationRecord
   validates :month_start_day, inclusion: { in: 1..28 }
   validates :moniker, inclusion: { in: MONIKERS }
   validates :assistant_type, inclusion: { in: ASSISTANT_TYPES }
+  validates :default_account_sharing, inclusion: { in: SHARING_DEFAULTS }
 
 
   def moniker_label
@@ -59,6 +61,10 @@ class Family < ApplicationRecord
     moniker_label == "Group" ? "Groups" : "Families"
   end
 
+  def share_all_by_default?
+    default_account_sharing == "shared"
+  end
+
   def uses_custom_month_start?
     month_start_day != 1
   end
@@ -115,12 +121,12 @@ class Family < ApplicationRecord
     AutoMerchantDetector.new(self, transaction_ids: transaction_ids).auto_detect
   end
 
-  def balance_sheet
-    @balance_sheet ||= BalanceSheet.new(self)
+  def balance_sheet(user: Current.user)
+    BalanceSheet.new(self, user: user)
   end
 
-  def income_statement
-    @income_statement ||= IncomeStatement.new(self)
+  def income_statement(user: Current.user)
+    IncomeStatement.new(self, user: user)
   end
 
   # Returns the Investment Contributions category for this family, creating it if it doesn't exist.
@@ -190,8 +196,8 @@ class Family < ApplicationRecord
     end
   end
 
-  def investment_statement
-    @investment_statement ||= InvestmentStatement.new(self)
+  def investment_statement(user: Current.user)
+    InvestmentStatement.new(self, user: user)
   end
 
   def eu?
diff --git a/app/models/family/sync_complete_event.rb b/app/models/family/sync_complete_event.rb
index 925384605..ef10e14dc 100644
--- a/app/models/family/sync_complete_event.rb
+++ b/app/models/family/sync_complete_event.rb
@@ -6,28 +6,11 @@ class Family::SyncCompleteEvent
   end
 
   def broadcast
-    # Dashboard partials can occasionally raise when rendered from background jobs
-    # (e.g., if intermediate series values are nil during a sync). Make broadcasts
-    # resilient so a post-sync UI refresh never causes the overall sync to report an error.
-    begin
-      family.broadcast_replace(
-        target: "balance-sheet",
-        partial: "pages/dashboard/balance_sheet",
-        locals: { balance_sheet: family.balance_sheet }
-      )
-    rescue => e
-      Rails.logger.error("Family::SyncCompleteEvent balance_sheet broadcast failed: #{e.message}\n#{e.backtrace&.join("\n")}")
-    end
-
-    begin
-      family.broadcast_replace(
-        target: "net-worth-chart",
-        partial: "pages/dashboard/net_worth_chart",
-        locals: { balance_sheet: family.balance_sheet, period: Period.last_30_days }
-      )
-    rescue => e
-      Rails.logger.error("Family::SyncCompleteEvent net_worth_chart broadcast failed: #{e.message}\n#{e.backtrace&.join("\n")}")
-    end
+    # Broadcast a refresh signal instead of rendered HTML. Each user's browser
+    # re-fetches via their own authenticated request, so the balance sheet and
+    # net worth chart are correctly scoped to the current user (Current.user is
+    # nil in background jobs, which would produce an unscoped family-wide view).
+    family.broadcast_refresh
 
     # Schedule recurring transaction pattern identification (debounced to run after all syncs complete)
     begin
diff --git a/app/models/income_statement.rb b/app/models/income_statement.rb
index 8f1b8f0a9..080d350ad 100644
--- a/app/models/income_statement.rb
+++ b/app/models/income_statement.rb
@@ -5,10 +5,11 @@ class IncomeStatement
 
   monetize :median_expense, :median_income
 
-  attr_reader :family
+  attr_reader :family, :user
 
-  def initialize(family)
+  def initialize(family, user: nil)
     @family = family
+    @user = user || Current.user
   end
 
   def totals(transactions_scope: nil, date_range:)
@@ -175,23 +176,28 @@ class IncomeStatement
     def family_stats(interval: "month")
       @family_stats ||= {}
       @family_stats[interval] ||= Rails.cache.fetch([
-        "income_statement", "family_stats", family.id, interval, family.entries_cache_version
-      ]) { FamilyStats.new(family, interval:).call }
+        "income_statement", "family_stats", family.id, user&.id, interval, family.entries_cache_version
+      ]) { FamilyStats.new(family, interval:, account_ids: included_account_ids).call }
     end
 
     def category_stats(interval: "month")
       @category_stats ||= {}
       @category_stats[interval] ||= Rails.cache.fetch([
-        "income_statement", "category_stats", family.id, interval, family.entries_cache_version
-      ]) { CategoryStats.new(family, interval:).call }
+        "income_statement", "category_stats", family.id, user&.id, interval, family.entries_cache_version
+      ]) { CategoryStats.new(family, interval:, account_ids: included_account_ids).call }
+    end
+
+    def included_account_ids
+      @included_account_ids ||= user ? user.finance_accounts.pluck(:id) : nil
     end
 
     def totals_query(transactions_scope:, date_range:)
       sql_hash = Digest::MD5.hexdigest(transactions_scope.to_sql)
+      account_ids_hash = included_account_ids ? Digest::MD5.hexdigest(included_account_ids.sort.join(",")) : nil
 
       Rails.cache.fetch([
-        "income_statement", "totals_query", "v2", family.id, sql_hash, family.entries_cache_version
-      ]) { Totals.new(family, transactions_scope: transactions_scope, date_range: date_range).call }
+        "income_statement", "totals_query", "v2", family.id, user&.id, account_ids_hash, sql_hash, family.entries_cache_version
+      ]) { Totals.new(family, transactions_scope: transactions_scope, date_range: date_range, included_account_ids: included_account_ids).call }
     end
 
     def monetizable_currency
diff --git a/app/models/income_statement/category_stats.rb b/app/models/income_statement/category_stats.rb
index 0476549e4..7fd2552c6 100644
--- a/app/models/income_statement/category_stats.rb
+++ b/app/models/income_statement/category_stats.rb
@@ -1,7 +1,8 @@
 class IncomeStatement::CategoryStats
-  def initialize(family, interval: "month")
+  def initialize(family, interval: "month", account_ids: nil)
     @family = family
     @interval = interval
+    @account_ids = account_ids
   end
 
   def call
@@ -48,6 +49,11 @@ class IncomeStatement::CategoryStats
       "AND a.id NOT IN (:tax_advantaged_account_ids)"
     end
 
+    def scope_to_account_ids_sql
+      return "" if @account_ids.blank?
+      ActiveRecord::Base.sanitize_sql([ "AND a.id IN (?)", @account_ids ])
+    end
+
     def query_sql
       <<~SQL
         WITH period_totals AS (
@@ -71,6 +77,7 @@ class IncomeStatement::CategoryStats
             AND (t.extra -> 'simplefin' ->> 'pending')::boolean IS DISTINCT FROM true
             AND (t.extra -> 'plaid' ->> 'pending')::boolean IS DISTINCT FROM true
             #{exclude_tax_advantaged_sql}
+            #{scope_to_account_ids_sql}
           GROUP BY c.id, period, CASE WHEN t.kind = 'investment_contribution' THEN 'expense' WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END
         )
         SELECT
diff --git a/app/models/income_statement/family_stats.rb b/app/models/income_statement/family_stats.rb
index 8ce0e2e2d..a8616ef96 100644
--- a/app/models/income_statement/family_stats.rb
+++ b/app/models/income_statement/family_stats.rb
@@ -1,7 +1,8 @@
 class IncomeStatement::FamilyStats
-  def initialize(family, interval: "month")
+  def initialize(family, interval: "month", account_ids: nil)
     @family = family
     @interval = interval
+    @account_ids = account_ids
   end
 
   def call
@@ -47,6 +48,11 @@ class IncomeStatement::FamilyStats
       "AND a.id NOT IN (:tax_advantaged_account_ids)"
     end
 
+    def scope_to_account_ids_sql
+      return "" if @account_ids.blank?
+      ActiveRecord::Base.sanitize_sql([ "AND a.id IN (?)", @account_ids ])
+    end
+
     def query_sql
       <<~SQL
         WITH period_totals AS (
@@ -68,6 +74,7 @@ class IncomeStatement::FamilyStats
             AND (t.extra -> 'simplefin' ->> 'pending')::boolean IS DISTINCT FROM true
             AND (t.extra -> 'plaid' ->> 'pending')::boolean IS DISTINCT FROM true
             #{exclude_tax_advantaged_sql}
+            #{scope_to_account_ids_sql}
           GROUP BY period, CASE WHEN t.kind = 'investment_contribution' THEN 'expense' WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END
         )
         SELECT
diff --git a/app/models/income_statement/totals.rb b/app/models/income_statement/totals.rb
index 398bd1377..54fb56732 100644
--- a/app/models/income_statement/totals.rb
+++ b/app/models/income_statement/totals.rb
@@ -1,14 +1,18 @@
 class IncomeStatement::Totals
-  def initialize(family, transactions_scope:, date_range:, include_trades: true)
+  def initialize(family, transactions_scope:, date_range:, include_trades: true, included_account_ids: nil)
     @family = family
     @transactions_scope = transactions_scope
     @date_range = date_range
     @include_trades = include_trades
+    @included_account_ids = included_account_ids
 
     validate_date_range!
   end
 
   def call
+    # No finance accounts means no transactions to report
+    return [] if @included_account_ids&.empty?
+
     ActiveRecord::Base.connection.select_all(query_sql).map do |row|
       TotalsRow.new(
         parent_category_id: row["parent_category_id"],
@@ -74,6 +78,7 @@ class IncomeStatement::Totals
           AND a.family_id = :family_id
           AND a.status IN ('draft', 'active')
           #{exclude_tax_advantaged_sql}
+          #{include_finance_accounts_sql}
         GROUP BY c.id, c.parent_id, CASE WHEN at.kind = 'investment_contribution' THEN 'expense' WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END;
       SQL
     end
@@ -105,6 +110,7 @@ class IncomeStatement::Totals
           AND a.family_id = :family_id
           AND a.status IN ('draft', 'active')
           #{exclude_tax_advantaged_sql}
+          #{include_finance_accounts_sql}
         GROUP BY c.id, c.parent_id, CASE WHEN at.kind = 'investment_contribution' THEN 'expense' WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END
       SQL
     end
@@ -133,6 +139,9 @@ class IncomeStatement::Totals
       ids = @family.tax_advantaged_account_ids
       params[:tax_advantaged_account_ids] = ids if ids.present?
 
+      # Add included account IDs for per-user finance scoping
+      params[:included_account_ids] = @included_account_ids if @included_account_ids
+
       params
     end
 
@@ -144,6 +153,12 @@ class IncomeStatement::Totals
       "AND a.id NOT IN (:tax_advantaged_account_ids)"
     end
 
+    # Returns SQL clause to filter to only accounts included in the user's finances.
+    def include_finance_accounts_sql
+      return "" if @included_account_ids.nil?
+      "AND a.id IN (:included_account_ids)"
+    end
+
     def budget_excluded_kinds_sql
       @budget_excluded_kinds_sql ||= Transaction::BUDGET_EXCLUDED_KINDS.map { |k| "'#{k}'" }.join(", ")
     end
diff --git a/app/models/investment_flow_statement.rb b/app/models/investment_flow_statement.rb
index d17a71266..66d68b7a9 100644
--- a/app/models/investment_flow_statement.rb
+++ b/app/models/investment_flow_statement.rb
@@ -1,21 +1,28 @@
 class InvestmentFlowStatement
   include Monetizable
 
-  attr_reader :family
+  attr_reader :family, :user
 
-  def initialize(family)
+  def initialize(family, user: nil)
     @family = family
+    @user = user
   end
 
   # Get contribution/withdrawal totals for a period
   def period_totals(period: Period.current_month)
-    transactions = family.transactions
+    scope = family.transactions
       .visible
       .excluding_pending
       .where(entries: { date: period.date_range })
       .where(kind: %w[standard investment_contribution])
       .where(investment_activity_label: %w[Contribution Withdrawal])
 
+    if user
+      scope = scope.joins(entry: :account).merge(Account.included_in_finances_for(user))
+    end
+
+    transactions = scope
+
     contributions = transactions.where(investment_activity_label: "Contribution").sum("entries.amount").abs
     withdrawals = transactions.where(investment_activity_label: "Withdrawal").sum("entries.amount").abs
 
diff --git a/app/models/investment_statement.rb b/app/models/investment_statement.rb
index 11cfdffa4..4475f1fce 100644
--- a/app/models/investment_statement.rb
+++ b/app/models/investment_statement.rb
@@ -5,17 +5,18 @@ class InvestmentStatement
 
   monetize :total_contributions, :total_dividends, :total_interest, :unrealized_gains
 
-  attr_reader :family
+  attr_reader :family, :user
 
-  def initialize(family)
+  def initialize(family, user: nil)
     @family = family
+    @user = user || Current.user
   end
 
   # Get totals for a specific period
   def totals(period: Period.current_month)
     trades_in_period = family.trades
       .joins(:entry)
-      .where(entries: { date: period.date_range })
+      .where(entries: { date: period.date_range, account_id: investment_account_ids })
 
     result = totals_query(trades_scope: trades_in_period)
 
@@ -161,7 +162,11 @@ class InvestmentStatement
 
   # Investment accounts
   def investment_accounts
-    @investment_accounts ||= family.accounts.visible.where(accountable_type: %w[Investment Crypto])
+    @investment_accounts ||= begin
+      scope = family.accounts.visible.where(accountable_type: %w[Investment Crypto])
+      scope = scope.included_in_finances_for(user) if user
+      scope
+    end
   end
 
   private
@@ -181,11 +186,15 @@ class InvestmentStatement
 
     HoldingAllocation = Data.define(:security, :amount, :weight, :trend)
 
+    def investment_account_ids
+      @investment_account_ids ||= investment_accounts.pluck(:id)
+    end
+
     def totals_query(trades_scope:)
       sql_hash = Digest::MD5.hexdigest(trades_scope.to_sql)
 
       Rails.cache.fetch([
-        "investment_statement", "totals_query", family.id, sql_hash, family.entries_cache_version
+        "investment_statement", "totals_query", family.id, user&.id, sql_hash, family.entries_cache_version
       ]) { Totals.new(family, trades_scope: trades_scope).call }
     end
 
diff --git a/app/models/invitation.rb b/app/models/invitation.rb
index 42bee7e9d..99ecb0da7 100644
--- a/app/models/invitation.rb
+++ b/app/models/invitation.rb
@@ -36,6 +36,7 @@ class Invitation < ApplicationRecord
     transaction do
       user.update!(family_id: family_id, role: role.to_s)
       update!(accepted_at: Time.current)
+      auto_share_existing_accounts(user) if family.share_all_by_default?
     end
     true
   end
@@ -95,4 +96,13 @@ class Invitation < ApplicationRecord
     def inviter_is_admin
       inviter.admin?
     end
+
+    def auto_share_existing_accounts(user)
+      records = family.accounts.where.not(owner_id: user.id).pluck(:id).map do |account_id|
+        { account_id: account_id, user_id: user.id, permission: "read_write",
+          include_in_finances: true, created_at: Time.current, updated_at: Time.current }
+      end
+
+      AccountShare.insert_all(records, unique_by: %i[account_id user_id]) if records.any?
+    end
 end
diff --git a/app/models/transaction/search.rb b/app/models/transaction/search.rb
index 5a9cf441e..442324461 100644
--- a/app/models/transaction/search.rb
+++ b/app/models/transaction/search.rb
@@ -16,10 +16,11 @@ class Transaction::Search
   attribute :tags, array: true
   attribute :active_accounts_only, :boolean, default: true
 
-  attr_reader :family
+  attr_reader :family, :accessible_account_ids
 
-  def initialize(family, filters: {})
+  def initialize(family, filters: {}, accessible_account_ids: nil)
     @family = family
+    @accessible_account_ids = accessible_account_ids
     super(filters)
   end
 
@@ -28,6 +29,9 @@ class Transaction::Search
       # This already joins entries + accounts. To avoid expensive double-joins, don't join them again (causes full table scan)
       query = family.transactions.merge(Entry.excluding_split_parents)
 
+      # Scope to accessible accounts when provided
+      query = query.where(entries: { account_id: accessible_account_ids }) if accessible_account_ids
+
       query = apply_active_accounts_filter(query, active_accounts_only)
       query = apply_category_filter(query, categories)
       query = apply_type_filter(query, types)
@@ -89,7 +93,8 @@ class Transaction::Search
       family.id,
       Digest::SHA256.hexdigest(attributes.sort.to_h.to_json), # cached by filters
       family.entries_cache_version,
-      Digest::SHA256.hexdigest(family.tax_advantaged_account_ids.sort.to_json) # stable across processes
+      Digest::SHA256.hexdigest(family.tax_advantaged_account_ids.sort.to_json), # stable across processes
+      accessible_account_ids ? Digest::SHA256.hexdigest(accessible_account_ids.sort.to_json) : "all"
     ].join("/")
   end
 
diff --git a/app/models/user.rb b/app/models/user.rb
index 752338bc2..8d7ed8414 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -34,6 +34,9 @@ class User < ApplicationRecord
   has_many :impersonated_support_sessions, class_name: "ImpersonationSession", foreign_key: :impersonated_id, dependent: :destroy
   has_many :oidc_identities, dependent: :destroy
   has_many :sso_audit_logs, dependent: :nullify
+  has_many :owned_accounts, class_name: "Account", foreign_key: :owner_id
+  has_many :account_shares, dependent: :destroy
+  has_many :shared_accounts, through: :account_shares, source: :account
   accepts_nested_attributes_for :family, update_only: true
 
   validates :email, presence: true, uniqueness: true, format: { with: URI::MailTo::EMAIL_REGEXP }
@@ -116,6 +119,14 @@ class User < ApplicationRecord
     super_admin? || role == "admin"
   end
 
+  def accessible_accounts
+    family.accounts.accessible_by(self)
+  end
+
+  def finance_accounts
+    family.accounts.included_in_finances_for(self)
+  end
+
   def display_name
     [ first_name, last_name ].compact.join(" ").presence || email
   end
@@ -194,6 +205,7 @@ class User < ApplicationRecord
     if last_user_in_family?
       family.destroy
     else
+      reassign_owned_accounts!
       destroy
     end
   end
@@ -400,6 +412,22 @@ class User < ApplicationRecord
       family.users.count == 1
     end
 
+    def reassign_owned_accounts!
+      account_ids = owned_accounts.pluck(:id)
+      return if account_ids.empty?
+
+      new_owner = family.users.where.not(id: id)
+                        .find_by(role: %w[admin super_admin]) ||
+                  family.users.where.not(id: id)
+                        .order(:created_at).first
+
+      return unless new_owner
+
+      Account.where(id: account_ids).update_all(owner_id: new_owner.id)
+      # Remove shares the new owner had for these accounts (they now own them)
+      AccountShare.where(account_id: account_ids, user_id: new_owner.id).delete_all
+    end
+
     def deactivated_email
       email.gsub(/@/, "-deactivated-#{SecureRandom.uuid}@")
     end
diff --git a/app/policies/account_policy.rb b/app/policies/account_policy.rb
new file mode 100644
index 000000000..2d1e5a036
--- /dev/null
+++ b/app/policies/account_policy.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+class AccountPolicy < ApplicationPolicy
+  def show?
+    record.shared_with?(user)
+  end
+
+  def create?
+    user.member? || user.admin?
+  end
+
+  def update?
+    permission = record.permission_for(user)
+    permission.in?([ :owner, :full_control ])
+  end
+
+  # For read_write users: categorize, tag, add notes/receipts on transactions
+  def annotate?
+    permission = record.permission_for(user)
+    permission.in?([ :owner, :full_control, :read_write ])
+  end
+
+  # Only the owner can delete the account itself.
+  # full_control users can delete transactions but not the account.
+  def destroy?
+    record.owned_by?(user)
+  end
+
+  def manage_sharing?
+    record.owned_by?(user)
+  end
+
+  class Scope < ApplicationPolicy::Scope
+    def resolve
+      scope.accessible_by(user)
+    end
+  end
+end
diff --git a/app/views/account_sharings/show.html.erb b/app/views/account_sharings/show.html.erb
new file mode 100644
index 000000000..0eb8524f7
--- /dev/null
+++ b/app/views/account_sharings/show.html.erb
@@ -0,0 +1,92 @@
+<%= render DS::Dialog.new do |dialog| %>
+  <% dialog.with_header(title: t(".title")) %>
+  <% dialog.with_body do %>
+    <% if @account.owned_by?(Current.user) %>
+      <% if @family_members.any? %>
+        <%= styled_form_with url: account_sharing_path(@account), method: :patch, class: "space-y-4" do |form| %>
+          <div class="bg-container-inset rounded-xl p-1">
+            <div class="px-4 py-2">
+              <div class="grid grid-cols-3 gap-4">
+                <p class="uppercase text-xs text-secondary font-medium"><%= t(".member") %></p>
+                <p class="uppercase text-xs text-secondary font-medium"><%= t(".permission") %></p>
+                <p class="uppercase text-xs text-secondary font-medium text-right"><%= t(".shared") %></p>
+              </div>
+            </div>
+            <% @family_members.each_with_index do |member, index| %>
+              <% share = @account_shares[member.id] %>
+              <div class="flex items-center bg-container p-4 shadow-border-xs rounded-lg mt-2">
+                <input type="hidden" name="sharing[members][<%= index %>][user_id]" value="<%= member.id %>">
+                <div class="grid grid-cols-3 gap-4 items-center w-full">
+                  <div class="flex items-center gap-2">
+                    <div class="w-8 h-8 rounded-full bg-surface-inset flex items-center justify-center text-xs font-medium text-secondary">
+                      <%= member.initials %>
+                    </div>
+                    <span id="member-name-<%= index %>" class="text-sm text-primary"><%= member.display_name %></span>
+                  </div>
+                  <div>
+                    <select name="sharing[members][<%= index %>][permission]" aria-labelledby="member-name-<%= index %>" class="text-sm border border-primary rounded-lg px-3 py-1.5 bg-container text-primary w-full">
+                      <% AccountShare::PERMISSIONS.each do |perm| %>
+                        <option value="<%= perm %>" <%= "selected" if share&.permission == perm %>>
+                          <%= t(".permissions.#{perm}") %>
+                        </option>
+                      <% end %>
+                    </select>
+                  </div>
+                  <div class="flex justify-end">
+                    <%= render DS::Toggle.new(
+                      id: "sharing_members_#{index}_shared",
+                      name: "sharing[members][#{index}][shared]",
+                      checked: share.present?,
+                      "aria-labelledby": "member-name-#{index}"
+                    ) %>
+                  </div>
+                </div>
+              </div>
+            <% end %>
+          </div>
+          <div class="flex justify-end">
+            <%= render DS::Button.new(text: t(".save"), class: "md:w-auto w-full justify-center") %>
+          </div>
+        <% end %>
+      <% else %>
+        <p class="text-sm text-secondary"><%= t(".no_members", moniker: family_moniker_downcase) %></p>
+      <% end %>
+    <% else %>
+      <%# Non-owner can only toggle finance inclusion %>
+      <% share = @account.account_shares.find_by(user: Current.user) %>
+      <% if share %>
+        <div class="space-y-4">
+          <div class="flex items-center gap-3">
+            <div class="w-8 h-8 rounded-full bg-surface-inset flex items-center justify-center text-xs font-medium text-secondary">
+              <%= @account.owner.initials %>
+            </div>
+            <div>
+              <p class="text-sm text-primary font-medium"><%= t(".owner_label", name: @account.owner.display_name) %></p>
+              <p class="text-xs text-secondary"><%= t(".permissions.#{share.permission}") %></p>
+            </div>
+          </div>
+
+          <%= styled_form_with url: account_sharing_path(@account), method: :patch, class: "space-y-4" do |form| %>
+            <input type="hidden" name="update_finance_inclusion" value="1">
+            <div class="bg-container-inset rounded-xl p-4">
+              <div class="flex items-center justify-between">
+                <div>
+                  <p class="text-sm text-primary font-medium"><%= t(".include_in_finances") %></p>
+                  <p class="text-xs text-secondary"><%= t(".finance_toggle_description") %></p>
+                </div>
+                <%= render DS::Toggle.new(
+                  id: "include_in_finances",
+                  name: "include_in_finances",
+                  checked: share.include_in_finances?
+                ) %>
+              </div>
+            </div>
+            <div class="flex justify-end">
+              <%= render DS::Button.new(text: t(".save"), class: "md:w-auto w-full justify-center") %>
+            </div>
+          <% end %>
+        </div>
+      <% end %>
+    <% end %>
+  <% end %>
+<% end %>
diff --git a/app/views/accounts/_account.html.erb b/app/views/accounts/_account.html.erb
index 82ce6b361..0dc54e788 100644
--- a/app/views/accounts/_account.html.erb
+++ b/app/views/accounts/_account.html.erb
@@ -21,6 +21,10 @@
           <div class="flex items-center gap-1.5">
             <%= link_to account.name, account, class: [(account.active? ? "text-primary" : "text-subdued"), "text-sm font-medium hover:underline"], data: { turbo_frame: "_top" } %>
 
+            <% if account.shared? %>
+              <%= icon("users", class: "w-3.5 h-3.5 text-secondary", title: account.owned_by?(Current.user) ? nil : account.owner&.display_name) %>
+            <% end %>
+
             <% if account.institution_name.present? %>
               <span class="hidden sm:inline text-secondary">• <%= account.institution_name %></span>
             <% end %>
@@ -56,21 +60,27 @@
           frame: :modal
         ) %>
       <% elsif !account.pending_deletion? %>
+        <% permission = account.permission_for(Current.user) %>
         <%= render DS::Menu.new(icon_vertical: true, mobile_fullwidth: false, max_width: "280px") do |menu| %>
-          <% menu.with_item(variant: "link", text: t("accounts.account.edit"), href: edit_account_path(account, return_to: return_to), icon: "pencil-line", data: { turbo_frame: :modal }) %>
-
-          <% if !account.linked? && %w[Depository CreditCard Investment Crypto].include?(account.accountable_type) %>
-            <% menu.with_item(variant: "link", text: t("accounts.account.link_provider"), href: select_provider_account_path(account), icon: "link", data: { turbo_frame: :modal }) %>
-          <% elsif account.linked? %>
-            <% menu.with_item(variant: "link", text: t("accounts.account.unlink_provider"), href: confirm_unlink_account_path(account), icon: "unlink", data: { turbo_frame: :modal }) %>
+          <% if permission.in?([ :owner, :full_control ]) %>
+            <% menu.with_item(variant: "link", text: t("accounts.account.edit"), href: edit_account_path(account, return_to: return_to), icon: "pencil-line", data: { turbo_frame: :modal }) %>
           <% end %>
+          <% menu.with_item(variant: "link", text: t("accounts.account.sharing"), href: account_sharing_path(account), icon: "users", data: { turbo_frame: :modal }) %>
 
-          <% menu.with_item(variant: "divider") %>
+          <% if permission.in?([ :owner, :full_control ]) %>
+            <% if !account.linked? && %w[Depository CreditCard Investment Crypto].include?(account.accountable_type) %>
+              <% menu.with_item(variant: "link", text: t("accounts.account.link_provider"), href: select_provider_account_path(account), icon: "link", data: { turbo_frame: :modal }) %>
+            <% elsif account.linked? %>
+              <% menu.with_item(variant: "link", text: t("accounts.account.unlink_provider"), href: confirm_unlink_account_path(account), icon: "unlink", data: { turbo_frame: :modal }) %>
+            <% end %>
 
-          <% if account.active? %>
-            <% menu.with_item(variant: "button", text: t("accounts.account.disable"), href: toggle_active_account_path(account), method: :patch, icon: "toggle-right", data: { turbo_frame: :_top }) %>
-          <% elsif account.disabled? %>
-            <% menu.with_item(variant: "button", text: t("accounts.account.enable"), href: toggle_active_account_path(account), method: :patch, icon: "toggle-left", data: { turbo_frame: :_top }) %>
+            <% menu.with_item(variant: "divider") %>
+
+            <% if account.active? %>
+              <% menu.with_item(variant: "button", text: t("accounts.account.disable"), href: toggle_active_account_path(account), method: :patch, icon: "toggle-right", data: { turbo_frame: :_top }) %>
+            <% elsif account.disabled? %>
+              <% menu.with_item(variant: "button", text: t("accounts.account.enable"), href: toggle_active_account_path(account), method: :patch, icon: "toggle-left", data: { turbo_frame: :_top }) %>
+            <% end %>
           <% end %>
 
           <% if is_default %>
@@ -79,7 +89,7 @@
             <% menu.with_item(variant: "button", text: t("accounts.account.set_default"), href: set_default_account_path(account), method: :patch, icon: "star", data: { turbo_frame: :_top }) %>
           <% end %>
 
-          <% unless account.linked? %>
+          <% if account.owned_by?(Current.user) && !account.linked? %>
             <% menu.with_item(variant: "divider") %>
             <% menu.with_item(variant: "button", text: t("accounts.account.delete"), href: account_path(account), method: :delete, icon: "trash-2", confirm: CustomConfirm.for_resource_deletion("account", high_severity: true), data: { turbo_frame: :_top }) %>
           <% end %>
diff --git a/app/views/accounts/_accountable_group.html.erb b/app/views/accounts/_accountable_group.html.erb
index 2ccea54a1..64f655797 100644
--- a/app/views/accounts/_accountable_group.html.erb
+++ b/app/views/accounts/_accountable_group.html.erb
@@ -34,6 +34,9 @@
           <div class="min-w-0 grow">
             <div class="flex items-center gap-2 mb-0.5">
               <%= tag.p account.name, class: class_names("text-sm text-primary font-medium truncate", "animate-pulse" => account.syncing?) %>
+              <% if account.shared? %>
+                <%= icon("users", class: "w-3 h-3 text-secondary shrink-0") %>
+              <% end %>
             </div>
             <%= tag.p account.short_subtype_label, class: "text-sm text-secondary truncate" %>
           </div>
diff --git a/app/views/accounts/index/_account_groups.erb b/app/views/accounts/index/_account_groups.erb
index b5ebcf7f4..a66ddf5e3 100644
--- a/app/views/accounts/index/_account_groups.erb
+++ b/app/views/accounts/index/_account_groups.erb
@@ -1,5 +1,6 @@
 <%# locals: (accounts:) %>
 
+<% ActiveRecord::Associations::Preloader.new(records: accounts, associations: :account_shares).call if accounts.any? %>
 <% accounts.group_by(&:accountable_type).sort_by { |group, _| group }.each do |group, accounts| %>
   <div class="bg-container-inset p-1 rounded-xl">
     <div class="flex items-center px-4 py-2 text-xs font-medium text-secondary">
diff --git a/app/views/accounts/show/_activity.html.erb b/app/views/accounts/show/_activity.html.erb
index ae8aeb8b2..76de75102 100644
--- a/app/views/accounts/show/_activity.html.erb
+++ b/app/views/accounts/show/_activity.html.erb
@@ -5,30 +5,32 @@
     <div class="flex items-center justify-between mb-4" data-testid="activity-menu">
       <%= tag.h2 t(".title"), class: "font-medium text-lg" %>
       <% unless @account.linked? %>
-        <%= render DS::Menu.new(variant: "button") do |menu| %>
-          <% menu.with_button(text: "New", variant: "secondary", icon: "plus") %>
+        <% if @account.permission_for(Current.user).in?([ :owner, :full_control ]) %>
+          <%= render DS::Menu.new(variant: "button") do |menu| %>
+            <% menu.with_button(text: "New", variant: "secondary", icon: "plus") %>
 
-          <% menu.with_item(
-              variant: "link",
-              text: "New balance",
-              icon: "circle-dollar-sign",
-              href: new_valuation_path(account_id: @account.id),
-              data: { turbo_frame: :modal }) %>
-
-          <% if @account.supports_trades? %>
             <% menu.with_item(
                 variant: "link",
-                text: t(".new_trade"),
-                icon: "credit-card",
-                href: new_trade_path(account_id: @account.id),
-                data: { turbo_frame: :modal }) %>
-          <% elsif !@account.crypto? %>
-            <% menu.with_item(
-                variant: "link",
-                text: t(".new_transaction"),
-                icon: "credit-card",
-                href: new_transaction_path(account_id: @account.id),
+                text: "New balance",
+                icon: "circle-dollar-sign",
+                href: new_valuation_path(account_id: @account.id),
                 data: { turbo_frame: :modal }) %>
+
+            <% if @account.supports_trades? %>
+              <% menu.with_item(
+                  variant: "link",
+                  text: t(".new_trade"),
+                  icon: "credit-card",
+                  href: new_trade_path(account_id: @account.id),
+                  data: { turbo_frame: :modal }) %>
+            <% elsif !@account.crypto? %>
+              <% menu.with_item(
+                  variant: "link",
+                  text: t(".new_transaction"),
+                  icon: "credit-card",
+                  href: new_transaction_path(account_id: @account.id),
+                  data: { turbo_frame: :modal }) %>
+            <% end %>
           <% end %>
         <% end %>
       <% end %>
diff --git a/app/views/accounts/show/_header.html.erb b/app/views/accounts/show/_header.html.erb
index 41d731236..cafd97811 100644
--- a/app/views/accounts/show/_header.html.erb
+++ b/app/views/accounts/show/_header.html.erb
@@ -9,6 +9,9 @@
         <div class="truncate">
           <div class="flex items-center gap-3">
             <h2 class="font-medium text-xl truncate <%= "animate-pulse" if account.syncing? %>"><%= title %></h2>
+            <% if account.shared? %>
+              <%= icon("users", class: "w-4 h-4 text-secondary", title: account.owned_by?(Current.user) ? nil : account.owner&.display_name) %>
+            <% end %>
             <% if account.tax_treatment.present? %>
               <%= render partial: "accounts/tax_treatment_badge", locals: { account: account } %>
             <% end %>
diff --git a/app/views/accounts/show/_menu.html.erb b/app/views/accounts/show/_menu.html.erb
index ee3db0c0d..45a39fe18 100644
--- a/app/views/accounts/show/_menu.html.erb
+++ b/app/views/accounts/show/_menu.html.erb
@@ -1,27 +1,33 @@
 <%# locals: (account:) %>
 
+<% permission = account.permission_for(Current.user) %>
 <%= render DS::Menu.new(testid: "account-menu") do |menu| %>
-  <% menu.with_item(variant: "link", text: "Edit", href: edit_account_path(account), icon: "pencil-line", data: { turbo_frame: :modal }) %>
+  <% if permission.in?([ :owner, :full_control ]) %>
+    <% menu.with_item(variant: "link", text: "Edit", href: edit_account_path(account), icon: "pencil-line", data: { turbo_frame: :modal }) %>
+  <% end %>
+  <% menu.with_item(variant: "link", text: "Sharing", href: account_sharing_path(account), icon: "users", data: { turbo_frame: :modal }) %>
 
-  <% if account.supports_trades? %>
-    <% menu.with_item(
-      variant: "link",
-      text: t(".import_trades"),
-      href: imports_path({ import: { type: "TradeImport", account_id: account.id } }),
-      icon: "download",
-      data: { turbo_frame: :_top }
-    ) %>
-  <% elsif !account.crypto? %>
-    <% menu.with_item(
-      variant: "link",
-      text: t(".import_transactions"),
-      href: imports_path({ import: { type: "TransactionImport", account_id: account.id } }),
-      icon: "download",
-      data: { turbo_frame: :_top }
-    ) %>
+  <% if permission.in?([ :owner, :full_control ]) %>
+    <% if account.supports_trades? %>
+      <% menu.with_item(
+        variant: "link",
+        text: t(".import_trades"),
+        href: imports_path({ import: { type: "TradeImport", account_id: account.id } }),
+        icon: "download",
+        data: { turbo_frame: :_top }
+      ) %>
+    <% elsif !account.crypto? %>
+      <% menu.with_item(
+        variant: "link",
+        text: t(".import_transactions"),
+        href: imports_path({ import: { type: "TransactionImport", account_id: account.id } }),
+        icon: "download",
+        data: { turbo_frame: :_top }
+      ) %>
+    <% end %>
   <% end %>
 
-  <% unless account.linked? %>
+  <% if account.owned_by?(Current.user) && !account.linked? %>
     <% menu.with_item(
       variant: "button",
       text: "Delete account",
diff --git a/app/views/imports/new.html.erb b/app/views/imports/new.html.erb
index f0a41ecc6..33d07ddfd 100644
--- a/app/views/imports/new.html.erb
+++ b/app/views/imports/new.html.erb
@@ -2,7 +2,7 @@
   <% dialog.with_header(title: t(".title"), subtitle: t(".description")) %>
 
   <% dialog.with_body do %>
-    <% has_accounts = Current.family.accounts.any? %>
+    <% has_accounts = accessible_accounts.any? %>
     <% requires_account_message = t(".requires_account") %>
 
     <% if @pending_import.present? && params[:type].nil? %>
diff --git a/app/views/pages/dashboard.html.erb b/app/views/pages/dashboard.html.erb
index 0a429d0b0..5df1313ef 100644
--- a/app/views/pages/dashboard.html.erb
+++ b/app/views/pages/dashboard.html.erb
@@ -29,8 +29,9 @@
   </div>
 <% end %>
 
+
 <div class="grid grid-cols-1 <%= "2xl:grid-cols-2" if Current.user.dashboard_two_column? %> gap-6 pb-6 lg:pb-12" data-controller="dashboard-sortable" data-action="dragover->dashboard-sortable#dragOver drop->dashboard-sortable#drop" role="list" aria-label="Dashboard sections">
-  <% if Current.family.accounts.any? %>
+  <% if accessible_accounts.any? %>
     <% @dashboard_sections.each do |section| %>
       <% next unless section[:visible] %>
       <section
diff --git a/app/views/settings/preferences/show.html.erb b/app/views/settings/preferences/show.html.erb
index eee21b87e..22faaf010 100644
--- a/app/views/settings/preferences/show.html.erb
+++ b/app/views/settings/preferences/show.html.erb
@@ -56,3 +56,22 @@
     <% end %>
   </div>
 <% end %>
+
+<% if Current.user.admin? %>
+  <%= settings_section title: t(".sharing_title", moniker: family_moniker), subtitle: t(".sharing_subtitle", moniker: family_moniker_downcase) do %>
+    <div>
+      <%= styled_form_with model: @user, class: "space-y-4", data: { controller: "auto-submit-form" } do |form| %>
+        <%= form.hidden_field :redirect_to, value: "preferences" %>
+        <%= form.fields_for :family do |family_form| %>
+          <%= family_form.select :default_account_sharing,
+              [
+                [t(".sharing_shared"), "shared"],
+                [t(".sharing_private"), "private"]
+              ],
+              { label: t(".sharing_default_label") },
+              { data: { auto_submit_form_target: "auto" } } %>
+        <% end %>
+      <% end %>
+    </div>
+  <% end %>
+<% end %>
diff --git a/app/views/trades/_form.html.erb b/app/views/trades/_form.html.erb
index 034e890bf..78c1b1b0b 100644
--- a/app/views/trades/_form.html.erb
+++ b/app/views/trades/_form.html.erb
@@ -45,7 +45,7 @@
       <% end %>
 
       <% if %w[deposit withdrawal].include?(type) %>
-        <%= form.collection_select :transfer_account_id, Current.family.accounts.visible.alphabetically, :id, :name, { prompt: t(".account_prompt"), label: t(".account") } %>
+        <%= form.collection_select :transfer_account_id, accessible_accounts.visible.alphabetically, :id, :name, { prompt: t(".account_prompt"), label: t(".account") } %>
       <% end %>
 
       <% if %w[buy sell].include?(type) %>
diff --git a/app/views/transaction_attachments/create.turbo_stream.erb b/app/views/transaction_attachments/create.turbo_stream.erb
index 571379426..f8a689461 100644
--- a/app/views/transaction_attachments/create.turbo_stream.erb
+++ b/app/views/transaction_attachments/create.turbo_stream.erb
@@ -1,4 +1,4 @@
-<%= turbo_stream.replace "transaction_attachments_#{@transaction.id}", partial: "transactions/attachments", locals: { transaction: @transaction } %>
+<%= turbo_stream.replace "transaction_attachments_#{@transaction.id}", partial: "transactions/attachments", locals: { transaction: @transaction, can_upload: @can_upload, can_delete: @can_delete } %>
 <% flash_notification_stream_items.each do |item| %>
   <%= item %>
 <% end %>
diff --git a/app/views/transaction_attachments/destroy.turbo_stream.erb b/app/views/transaction_attachments/destroy.turbo_stream.erb
index 571379426..f8a689461 100644
--- a/app/views/transaction_attachments/destroy.turbo_stream.erb
+++ b/app/views/transaction_attachments/destroy.turbo_stream.erb
@@ -1,4 +1,4 @@
-<%= turbo_stream.replace "transaction_attachments_#{@transaction.id}", partial: "transactions/attachments", locals: { transaction: @transaction } %>
+<%= turbo_stream.replace "transaction_attachments_#{@transaction.id}", partial: "transactions/attachments", locals: { transaction: @transaction, can_upload: @can_upload, can_delete: @can_delete } %>
 <% flash_notification_stream_items.each do |item| %>
   <%= item %>
 <% end %>
diff --git a/app/views/transactions/_attachments.html.erb b/app/views/transactions/_attachments.html.erb
index 8688e6285..dba4b464f 100644
--- a/app/views/transactions/_attachments.html.erb
+++ b/app/views/transactions/_attachments.html.erb
@@ -1,6 +1,8 @@
+<%# locals: (transaction:, can_upload: false, can_delete: false) %>
+
 <div id="transaction_attachments_<%= transaction.id %>" class="pb-4">
   <!-- Upload Form -->
-  <% if transaction.attachments.count < Transaction::MAX_ATTACHMENTS_PER_TRANSACTION %>
+  <% if can_upload && transaction.attachments.count < Transaction::MAX_ATTACHMENTS_PER_TRANSACTION %>
     <%= styled_form_with url: transaction_attachments_path(transaction),
           method: :post,
           multipart: true,
@@ -54,7 +56,7 @@
         </div>
       </div>
     <% end %>
-  <% else %>
+  <% elsif can_upload %>
     <div class="p-3 mb-4 rounded-lg border border-warning bg-warning/5 flex items-start gap-3">
       <%= icon "alert-circle", size: "sm", color: "warning", class: "mt-0.5" %>
       <div class="text-xs text-warning leading-relaxed font-medium">
@@ -103,14 +105,16 @@
                     data: { turbo: false }
                   ) %>
 
-              <%= render DS::Button.new(
-                    href: transaction_attachment_path(transaction, attachment),
-                    method: :delete,
-                    variant: :outline_destructive,
-                    size: :sm,
-                    icon: "trash-2",
-                    confirm: CustomConfirm.for_resource_deletion("attachment")
-                  ) %>
+              <% if can_delete %>
+                <%= render DS::Button.new(
+                      href: transaction_attachment_path(transaction, attachment),
+                      method: :delete,
+                      variant: :outline_destructive,
+                      size: :sm,
+                      icon: "trash-2",
+                      confirm: CustomConfirm.for_resource_deletion("attachment")
+                    ) %>
+              <% end %>
             </div>
           </div>
         <% end %>
diff --git a/app/views/transactions/_form.html.erb b/app/views/transactions/_form.html.erb
index 7bfde6e9a..cc7466898 100644
--- a/app/views/transactions/_form.html.erb
+++ b/app/views/transactions/_form.html.erb
@@ -18,7 +18,7 @@
     <% if @entry.account_id %>
       <%= f.hidden_field :account_id %>
     <% else %>
-      <%= f.collection_select :account_id, Current.family.accounts.manual.active.alphabetically, :id, :name, { prompt: t(".account_prompt"), label: t(".account"), selected: Current.user.default_account_for_transactions&.id, variant: :logo }, required: true, class: "form-field__input text-ellipsis" %>
+      <%= f.collection_select :account_id, accessible_accounts.manual.active.alphabetically, :id, :name, { prompt: t(".account_prompt"), label: t(".account"), selected: Current.user.default_account_for_transactions&.id, variant: :logo }, required: true, class: "form-field__input text-ellipsis" %>
     <% end %>
 
     <%= f.money_field :amount, label: t(".amount"), required: true %>
diff --git a/app/views/transactions/searches/filters/_account_filter.html.erb b/app/views/transactions/searches/filters/_account_filter.html.erb
index 8182dedcd..4641a3ddb 100644
--- a/app/views/transactions/searches/filters/_account_filter.html.erb
+++ b/app/views/transactions/searches/filters/_account_filter.html.erb
@@ -5,7 +5,7 @@
     <%= icon("search", class: "absolute inset-y-0 left-2 top-1/2 transform -translate-y-1/2") %>
   </div>
   <div class="my-2" id="list" data-list-filter-target="list">
-    <% Current.family.accounts.alphabetically.each do |account| %>
+    <% Current.user.accessible_accounts.alphabetically.each do |account| %>
       <div class="filterable-item flex items-center gap-2 p-2" data-filter-name="<%= account.name %>">
         <%= form.check_box :accounts,
                            {
diff --git a/app/views/transactions/show.html.erb b/app/views/transactions/show.html.erb
index eab1586d2..4f8854fdf 100644
--- a/app/views/transactions/show.html.erb
+++ b/app/views/transactions/show.html.erb
@@ -48,32 +48,34 @@
     <% dialog.with_section(title: t(".overview"), open: true) do %>
       <div>
         <% split_locked = @entry.split_child? || @entry.split_parent? %>
+        <% edit_locked = !can_edit_entry? %>
+        <% annotate_locked = !can_annotate_entry? %>
         <%= styled_form_with model: @entry,
               url: transaction_path(@entry),
               class: "space-y-2",
               data: { controller: "auto-submit-form" } do |f| %>
           <%= f.text_field :name,
                 label: t(".name_label"),
-                disabled: @entry.split_child?,
+                disabled: @entry.split_child? || edit_locked,
                 "data-auto-submit-form-target": "auto" %>
           <%= f.date_field :date,
                 label: t(".date_label"),
                 max: Date.current,
-                disabled: @entry.linked? || split_locked,
+                disabled: @entry.linked? || split_locked || edit_locked,
                 "data-auto-submit-form-target": "auto" %>
           <% unless @entry.transaction.transfer? %>
             <div class="flex items-center gap-2">
               <%= f.select :nature,
                     [["Expense", "outflow"], ["Income", "inflow"]],
                     { container_class: "w-1/3", label: t(".nature"), selected: @entry.amount.negative? ? "inflow" : "outflow" },
-                    { data: { "auto-submit-form-target": "auto" }, disabled: @entry.linked? || split_locked } %>
+                    { data: { "auto-submit-form-target": "auto" }, disabled: @entry.linked? || split_locked || edit_locked } %>
               <%= f.money_field :amount, label: t(".amount"),
                     container_class: "w-2/3",
                     auto_submit: true,
                     min: 0,
                     value: @entry.amount.abs,
-                    disabled: @entry.linked? || split_locked,
-                    disable_currency: @entry.linked? || split_locked %>
+                    disabled: @entry.linked? || split_locked || edit_locked,
+                    disable_currency: @entry.linked? || split_locked || edit_locked %>
             </div>
             <%= f.fields_for :entryable do |ef| %>
               <%= ef.collection_select :category_id,
@@ -81,7 +83,7 @@
                     :id, :name,
                     { label: t(".category_label"),
                       class: "text-subdued", include_blank: t(".uncategorized"),
-                      variant: :badge, searchable: true, disabled: @entry.split_child? },
+                      variant: :badge, searchable: true, disabled: @entry.split_child? || annotate_locked },
                     "data-auto-submit-form-target": "auto" %>
             <% end %>
           <% end %>
@@ -96,7 +98,7 @@
         <% unless @entry.transaction.transfer? %>
           <%= f.select :account,
               options_for_select(
-                Current.family.accounts.alphabetically.pluck(:name, :id),
+                accessible_accounts.alphabetically.pluck(:name, :id),
                 @entry.account_id
               ),
               { label: t(".account_label") },
@@ -107,7 +109,7 @@
                   :id, :name,
                   { include_blank: t(".none"),
                     label: t(".merchant_label"),
-                    class: "text-subdued", variant: :logo, searchable: true, disabled: @entry.split_child? },
+                    class: "text-subdued", variant: :logo, searchable: true, disabled: @entry.split_child? || !can_annotate_entry? },
                   "data-auto-submit-form-target": "auto" %>
             <%= ef.select :tag_ids,
                   Current.family.tags.alphabetically.pluck(:name, :id),
@@ -115,7 +117,7 @@
                     include_blank: t(".none"),
                     multiple: true,
                     label:    t(".tags_label"),
-                    disabled: @entry.split_child?
+                    disabled: @entry.split_child? || !can_annotate_entry?
                   },
                   { "data-controller": "multi-select", "data-auto-submit-form-target": "auto" } %>
           <% end %>
@@ -124,13 +126,13 @@
                 label: t(".note_label"),
                 placeholder: t(".note_placeholder"),
                 rows: 5,
-                disabled: @entry.split_child?,
+                disabled: @entry.split_child? || !can_annotate_entry?,
                 "data-auto-submit-form-target": "auto" %>
       <% end %>
     <% end %>
 
     <% dialog.with_section(title: t(".attachments")) do %>
-      <%= render "transactions/attachments", transaction: @entry.transaction %>
+      <%= render "transactions/attachments", transaction: @entry.transaction, can_upload: can_annotate_entry?, can_delete: can_edit_entry? %>
     <% end %>
 
     <% if (details = build_transaction_extra_details(@entry)) %>
@@ -263,166 +265,168 @@
       <% end %>
     <% end %>
 
-    <% dialog.with_section(title: t(".settings")) do %>
-      <% unless @entry.split_parent? || @entry.split_child? %>
-        <div class="pb-4">
-          <%= styled_form_with model: @entry,
-                url: transaction_path(@entry),
-                class: "p-3",
-                data: { controller: "auto-submit-form" } do |f| %>
-            <div class="flex cursor-pointer items-center gap-4 justify-between">
-              <div class="text-sm space-y-1">
-                <h4 class="text-primary"><%= t(".exclude") %></h4>
-                <p class="text-secondary"><%= t(".exclude_description") %></p>
-              </div>
-              <%= f.toggle :excluded, { data: { auto_submit_form_target: "auto" } } %>
-            </div>
-          <% end %>
-        </div>
-      <% end %>
-      <% if @entry.account.investment? || @entry.account.crypto? %>
-        <div class="pb-4">
-          <%= styled_form_with model: @entry,
-                url: transaction_path(@entry),
-                class: "p-3",
-                data: { controller: "auto-submit-form" } do |f| %>
-            <%= f.fields_for :entryable do |ef| %>
+    <% if can_edit_entry? %>
+      <% dialog.with_section(title: t(".settings")) do %>
+        <% unless @entry.split_parent? || @entry.split_child? %>
+          <div class="pb-4">
+            <%= styled_form_with model: @entry,
+                  url: transaction_path(@entry),
+                  class: "p-3",
+                  data: { controller: "auto-submit-form" } do |f| %>
               <div class="flex cursor-pointer items-center gap-4 justify-between">
                 <div class="text-sm space-y-1">
-                  <h4 class="text-primary"><%= t(".activity_type") %></h4>
-                  <p class="text-secondary"><%= t(".activity_type_description") %></p>
+                  <h4 class="text-primary"><%= t(".exclude") %></h4>
+                  <p class="text-secondary"><%= t(".exclude_description") %></p>
                 </div>
-                <%= ef.select :investment_activity_label,
-                      options_for_select(
-                        [["—", nil]] + Transaction::ACTIVITY_LABELS.map { |l| [t("transactions.activity_labels.#{l.parameterize(separator: '_')}"), l] },
-                        @entry.entryable.investment_activity_label
-                      ),
-                      { label: false },
-                      { class: "form-field__input border border-secondary rounded-lg px-3 py-1.5 max-w-40 text-sm",
-                        data: { auto_submit_form_target: "auto" } } %>
+                <%= f.toggle :excluded, { data: { auto_submit_form_target: "auto" } } %>
               </div>
             <% end %>
-          <% end %>
-        </div>
-      <% end %>
-      <% unless @entry.split_child? %>
-        <div class="pb-4">
-          <%= styled_form_with model: @entry,
-                url: transaction_path(@entry),
-                class: "p-3",
-                data: { controller: "auto-submit-form" } do |f| %>
-            <%= f.fields_for :entryable do |ef| %>
-              <div class="flex cursor-pointer items-center gap-4 justify-between">
-                <div class="text-sm space-y-1">
-                  <h4 class="text-primary"><%= t(".one_time_title", type: @entry.amount.negative? ? t("transactions.form.income") : t("transactions.form.expense")) %></h4>
-                  <p class="text-secondary"><%= t(".one_time_description") %></p>
+          </div>
+        <% end %>
+        <% if @entry.account.investment? || @entry.account.crypto? %>
+          <div class="pb-4">
+            <%= styled_form_with model: @entry,
+                  url: transaction_path(@entry),
+                  class: "p-3",
+                  data: { controller: "auto-submit-form" } do |f| %>
+              <%= f.fields_for :entryable do |ef| %>
+                <div class="flex cursor-pointer items-center gap-4 justify-between">
+                  <div class="text-sm space-y-1">
+                    <h4 class="text-primary"><%= t(".activity_type") %></h4>
+                    <p class="text-secondary"><%= t(".activity_type_description") %></p>
+                  </div>
+                  <%= ef.select :investment_activity_label,
+                        options_for_select(
+                          [["—", nil]] + Transaction::ACTIVITY_LABELS.map { |l| [t("transactions.activity_labels.#{l.parameterize(separator: '_')}"), l] },
+                          @entry.entryable.investment_activity_label
+                        ),
+                        { label: false },
+                        { class: "form-field__input border border-secondary rounded-lg px-3 py-1.5 max-w-40 text-sm",
+                          data: { auto_submit_form_target: "auto" } } %>
                 </div>
-                <%= ef.toggle :kind, {
-                      checked: @entry.transaction.one_time?,
-                      data: { auto_submit_form_target: "auto" }
-                    }, "one_time", "standard" %>
-              </div>
+              <% end %>
             <% end %>
-          <% end %>
-        </div>
-      <% end %>
-      <%# Split Transaction %>
-      <% if @entry.transaction.splittable? %>
-        <div class="flex items-center justify-between gap-4 p-3">
-          <div class="text-sm space-y-1">
-            <h4 class="text-primary"><%= t("splits.show.button_title") %></h4>
-            <p class="text-secondary"><%= t("splits.show.button_description") %></p>
           </div>
-          <%= render DS::Link.new(
-            text: t("splits.show.button"),
-            icon: "split",
-            variant: "outline",
-            href: new_transaction_split_path(@entry),
-            frame: :modal
-          ) %>
-        </div>
-      <% end %>
-      <% unless @entry.split_child? %>
-        <div class="flex items-center justify-between gap-4 p-3">
-          <div class="text-sm space-y-1">
-            <h4 class="text-primary">Transfer or Debt Payment?</h4>
-            <p class="text-secondary">Transfers and payments are special types of transactions that indicate money movement between 2 accounts.</p>
+        <% end %>
+        <% unless @entry.split_child? %>
+          <div class="pb-4">
+            <%= styled_form_with model: @entry,
+                  url: transaction_path(@entry),
+                  class: "p-3",
+                  data: { controller: "auto-submit-form" } do |f| %>
+              <%= f.fields_for :entryable do |ef| %>
+                <div class="flex cursor-pointer items-center gap-4 justify-between">
+                  <div class="text-sm space-y-1">
+                    <h4 class="text-primary"><%= t(".one_time_title", type: @entry.amount.negative? ? t("transactions.form.income") : t("transactions.form.expense")) %></h4>
+                    <p class="text-secondary"><%= t(".one_time_description") %></p>
+                  </div>
+                  <%= ef.toggle :kind, {
+                        checked: @entry.transaction.one_time?,
+                        data: { auto_submit_form_target: "auto" }
+                      }, "one_time", "standard" %>
+                </div>
+              <% end %>
+            <% end %>
           </div>
-          <%= render DS::Link.new(
-            text: "Open matcher",
-            icon: "arrow-left-right",
-            variant: "outline",
-            href: new_transaction_transfer_match_path(@entry),
-            frame: :modal
-          ) %>
-        </div>
-        <!-- Pending Duplicate Merger -->
-        <% if @entry.entryable.is_a?(Transaction) && @entry.entryable.pending? %>
+        <% end %>
+        <%# Split Transaction %>
+        <% if @entry.transaction.splittable? %>
           <div class="flex items-center justify-between gap-4 p-3">
             <div class="text-sm space-y-1">
-              <h4 class="text-primary"><%= t("transactions.show.pending_duplicate_merger_title") %></h4>
-              <p class="text-secondary"><%= t("transactions.show.pending_duplicate_merger_description") %></p>
+              <h4 class="text-primary"><%= t("splits.show.button_title") %></h4>
+              <p class="text-secondary"><%= t("splits.show.button_description") %></p>
             </div>
             <%= render DS::Link.new(
-              text: t("transactions.show.pending_duplicate_merger_button"),
-              icon: "merge",
+              text: t("splits.show.button"),
+              icon: "split",
               variant: "outline",
-              href: new_transaction_pending_duplicate_merges_path(@entry),
+              href: new_transaction_split_path(@entry),
               frame: :modal
             ) %>
           </div>
         <% end %>
-        <!-- Convert to Trade (Investment Accounts Only, not already converted) -->
-        <% if @entry.account.investment? && @entry.entryable.is_a?(Transaction) && !@entry.excluded? %>
+        <% unless @entry.split_child? %>
+          <div class="flex items-center justify-between gap-4 p-3">
+            <div class="text-sm space-y-1">
+              <h4 class="text-primary">Transfer or Debt Payment?</h4>
+              <p class="text-secondary">Transfers and payments are special types of transactions that indicate money movement between 2 accounts.</p>
+            </div>
+            <%= render DS::Link.new(
+              text: "Open matcher",
+              icon: "arrow-left-right",
+              variant: "outline",
+              href: new_transaction_transfer_match_path(@entry),
+              frame: :modal
+            ) %>
+          </div>
+          <!-- Pending Duplicate Merger -->
+          <% if @entry.entryable.is_a?(Transaction) && @entry.entryable.pending? %>
+            <div class="flex items-center justify-between gap-4 p-3">
+              <div class="text-sm space-y-1">
+                <h4 class="text-primary"><%= t("transactions.show.pending_duplicate_merger_title") %></h4>
+                <p class="text-secondary"><%= t("transactions.show.pending_duplicate_merger_description") %></p>
+              </div>
+              <%= render DS::Link.new(
+                text: t("transactions.show.pending_duplicate_merger_button"),
+                icon: "merge",
+                variant: "outline",
+                href: new_transaction_pending_duplicate_merges_path(@entry),
+                frame: :modal
+              ) %>
+            </div>
+          <% end %>
+          <!-- Convert to Trade (Investment Accounts Only, not already converted) -->
+          <% if @entry.account.investment? && @entry.entryable.is_a?(Transaction) && !@entry.excluded? %>
+            <div class="flex items-center justify-between gap-2 p-3">
+              <div class="text-sm space-y-1">
+                <h4 class="text-primary">Convert to Security Trade</h4>
+                <p class="text-secondary">Convert this transaction into a security trade (buy/sell) by providing ticker, shares, and price.</p>
+              </div>
+              <%= render DS::Button.new(
+                text: "Convert",
+                variant: "outline",
+                icon: "arrow-right-left",
+                href: convert_to_trade_transaction_path(@entry.transaction),
+                method: :get,
+                frame: :modal
+              ) %>
+            </div>
+          <% end %>
+          <!-- Mark as Recurring Form -->
           <div class="flex items-center justify-between gap-2 p-3">
             <div class="text-sm space-y-1">
-              <h4 class="text-primary">Convert to Security Trade</h4>
-              <p class="text-secondary">Convert this transaction into a security trade (buy/sell) by providing ticker, shares, and price.</p>
+              <h4 class="text-primary"><%= t(".mark_recurring_title") %></h4>
+              <p class="text-secondary"><%= t(".mark_recurring_subtitle") %></p>
             </div>
             <%= render DS::Button.new(
-              text: "Convert",
+              text: t(".mark_recurring"),
               variant: "outline",
-              icon: "arrow-right-left",
-              href: convert_to_trade_transaction_path(@entry.transaction),
-              method: :get,
-              frame: :modal
+              icon: "repeat",
+              href: mark_as_recurring_transaction_path(@entry.transaction),
+              method: :post,
+              frame: "_top"
             ) %>
           </div>
         <% end %>
-        <!-- Mark as Recurring Form -->
-        <div class="flex items-center justify-between gap-2 p-3">
-          <div class="text-sm space-y-1">
-            <h4 class="text-primary"><%= t(".mark_recurring_title") %></h4>
-            <p class="text-secondary"><%= t(".mark_recurring_subtitle") %></p>
+        <%# Delete Transaction Form - hidden for split children %>
+        <% unless @entry.split_child? %>
+          <div class="flex items-center justify-between gap-2 p-3">
+            <div class="text-sm space-y-1">
+              <h4 class="text-primary"><%= t(".delete_title") %></h4>
+              <p class="text-secondary"><%= t(".delete_subtitle") %></p>
+            </div>
+            <%= render DS::Button.new(
+              text: t(".delete"),
+              variant: "outline-destructive",
+              href: entry_path(@entry),
+              method: :delete,
+              confirm: CustomConfirm.for_resource_deletion("transaction"),
+              frame: "_top"
+            ) %>
           </div>
-          <%= render DS::Button.new(
-            text: t(".mark_recurring"),
-            variant: "outline",
-            icon: "repeat",
-            href: mark_as_recurring_transaction_path(@entry.transaction),
-            method: :post,
-            frame: "_top"
-          ) %>
+        <% end %>
         </div>
       <% end %>
-      <%# Delete Transaction Form - hidden for split children %>
-      <% unless @entry.split_child? %>
-        <div class="flex items-center justify-between gap-2 p-3">
-          <div class="text-sm space-y-1">
-            <h4 class="text-primary"><%= t(".delete_title") %></h4>
-            <p class="text-secondary"><%= t(".delete_subtitle") %></p>
-          </div>
-          <%= render DS::Button.new(
-            text: t(".delete"),
-            variant: "outline-destructive",
-            href: entry_path(@entry),
-            method: :delete,
-            confirm: CustomConfirm.for_resource_deletion("transaction"),
-            frame: "_top"
-          ) %>
-        </div>
-      <% end %>
-      </div>
     <% end %>
   <% end %>
 <% end %>
diff --git a/config/locales/views/account_sharings/en.yml b/config/locales/views/account_sharings/en.yml
new file mode 100644
index 000000000..2a219a054
--- /dev/null
+++ b/config/locales/views/account_sharings/en.yml
@@ -0,0 +1,29 @@
+---
+en:
+  account_sharings:
+    show:
+      title: Account Sharing
+      subtitle: Control who can see and interact with this account
+      member: Member
+      permission: Permission
+      shared: Shared
+      no_members: No other members in your %{moniker} to share with
+      permissions:
+        full_control: Full control
+        full_control_description: Can view, edit, and manage transactions
+        read_write: Can annotate
+        read_write_description: Can categorize, tag, and add notes
+        read_only: View only
+        read_only_description: Can only view account data
+      save: Save sharing settings
+      owner_label: "Owner: %{name}"
+      shared_with_count:
+        one: Shared with 1 member
+        other: "Shared with %{count} members"
+      include_in_finances: Include in my budgets & reports
+      exclude_from_finances: Exclude from my budgets & reports
+      finance_toggle_description: Count this account in your net worth, budgets, and reports
+    update:
+      success: Sharing settings updated
+      not_owner: Only the account owner can manage sharing
+      finance_toggle_success: Finance inclusion preference updated
diff --git a/config/locales/views/accounts/en.yml b/config/locales/views/accounts/en.yml
index 1a721e19a..e64f84972 100644
--- a/config/locales/views/accounts/en.yml
+++ b/config/locales/views/accounts/en.yml
@@ -1,6 +1,7 @@
 ---
 en:
   accounts:
+    not_authorized: "You don't have permission to manage this account"
     account:
       edit: Edit
       link_lunchflow: Link with Lunch Flow
@@ -13,6 +14,7 @@ en:
       remove_default: Unset default
       default_label: Default
       delete: Delete account
+      sharing: Sharing
     chart:
       data_not_available: Data not available for the selected period
     create:
diff --git a/config/locales/views/settings/en.yml b/config/locales/views/settings/en.yml
index 9dada3442..d590798ca 100644
--- a/config/locales/views/settings/en.yml
+++ b/config/locales/views/settings/en.yml
@@ -58,6 +58,11 @@ en:
         month_start_day: Budget month starts on
         month_start_day_hint: Set when your budget month starts (e.g., payday)
         month_start_day_warning: Your budgets and MTD calculations will use this custom start day instead of the 1st of each month.
+        sharing_title: "%{moniker} Sharing"
+        sharing_subtitle: "Control how accounts are shared in your %{moniker}"
+        sharing_default_label: Default sharing for new accounts
+        sharing_shared: Share with all members
+        sharing_private: Keep private by default
     profiles:
       destroy:
         cannot_remove_self: You cannot remove yourself from the account.
diff --git a/config/routes.rb b/config/routes.rb
index 9ef960239..8514a9407 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -348,6 +348,8 @@ Rails.application.routes.draw do
     collection do
       post :sync_all
     end
+
+    resource :sharing, only: [ :show, :update ], controller: "account_sharings"
   end
 
   # Convenience routes for polymorphic paths
diff --git a/db/migrate/20260324100000_add_account_sharing_support.rb b/db/migrate/20260324100000_add_account_sharing_support.rb
new file mode 100644
index 000000000..253606850
--- /dev/null
+++ b/db/migrate/20260324100000_add_account_sharing_support.rb
@@ -0,0 +1,21 @@
+class AddAccountSharingSupport < ActiveRecord::Migration[7.2]
+  def change
+    # Family-level default: whether new accounts are shared with all members by default
+    add_column :families, :default_account_sharing, :string, default: "shared", null: false
+
+    # Account ownership: who created/owns the account
+    add_reference :accounts, :owner, type: :uuid, foreign_key: { to_table: :users }, null: true, index: true
+
+    # Sharing join table: per-user access to accounts they don't own
+    create_table :account_shares, id: :uuid, default: -> { "gen_random_uuid()" } do |t|
+      t.references :account, type: :uuid, null: false, foreign_key: true
+      t.references :user, type: :uuid, null: false, foreign_key: true
+      t.string :permission, null: false, default: "read_only"
+      t.boolean :include_in_finances, null: false, default: true
+      t.timestamps
+    end
+
+    add_index :account_shares, [ :account_id, :user_id ], unique: true
+    add_index :account_shares, [ :user_id, :include_in_finances ]
+  end
+end
diff --git a/db/migrate/20260324100001_backfill_account_owners_and_shares.rb b/db/migrate/20260324100001_backfill_account_owners_and_shares.rb
new file mode 100644
index 000000000..8ed6b0416
--- /dev/null
+++ b/db/migrate/20260324100001_backfill_account_owners_and_shares.rb
@@ -0,0 +1,34 @@
+class BackfillAccountOwnersAndShares < ActiveRecord::Migration[7.2]
+  def up
+    # Existing families keep current behavior: all accounts shared
+    Family.update_all(default_account_sharing: "shared")
+
+    # For each family, assign all accounts to the admin (or first user)
+    Family.find_each do |family|
+      admin = family.users.find_by(role: %w[admin super_admin]) || family.users.order(:created_at).first
+      next unless admin
+
+      family.accounts.where(owner_id: nil).update_all(owner_id: admin.id)
+
+      # Create shares for non-owner members (preserves current full-access behavior)
+      member_ids = family.users.where.not(id: admin.id).pluck(:id)
+      account_ids = family.accounts.pluck(:id)
+
+      if member_ids.any? && account_ids.any?
+        records = member_ids.product(account_ids).map do |user_id, account_id|
+          { user_id: user_id, account_id: account_id, permission: "full_control",
+            include_in_finances: true, created_at: Time.current, updated_at: Time.current }
+        end
+
+        AccountShare.upsert_all(records, unique_by: %i[account_id user_id])
+      end
+    end
+
+    # Owner is enforced at the model level via before_validation callback
+    # Keeping nullable at DB level for backward compatibility with tests/seeds
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end
diff --git a/db/migrate/20260324100002_add_check_constraints_to_sharing_columns.rb b/db/migrate/20260324100002_add_check_constraints_to_sharing_columns.rb
new file mode 100644
index 000000000..0a21a4113
--- /dev/null
+++ b/db/migrate/20260324100002_add_check_constraints_to_sharing_columns.rb
@@ -0,0 +1,6 @@
+class AddCheckConstraintsToSharingColumns < ActiveRecord::Migration[7.2]
+  def change
+    add_check_constraint :families, "default_account_sharing IN ('shared', 'private')", name: "chk_families_default_account_sharing"
+    add_check_constraint :account_shares, "permission IN ('full_control', 'read_write', 'read_only')", name: "chk_account_shares_permission"
+  end
+end
diff --git a/db/migrate/20260324100003_change_accounts_owner_fk_to_nullify.rb b/db/migrate/20260324100003_change_accounts_owner_fk_to_nullify.rb
new file mode 100644
index 000000000..bd2ce4298
--- /dev/null
+++ b/db/migrate/20260324100003_change_accounts_owner_fk_to_nullify.rb
@@ -0,0 +1,11 @@
+class ChangeAccountsOwnerFkToNullify < ActiveRecord::Migration[7.2]
+  def up
+    remove_foreign_key :accounts, :users, column: :owner_id
+    add_foreign_key :accounts, :users, column: :owner_id, on_delete: :nullify
+  end
+
+  def down
+    remove_foreign_key :accounts, :users, column: :owner_id
+    add_foreign_key :accounts, :users, column: :owner_id
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 8355c6564..fce042e9c 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
+ActiveRecord::Schema[7.2].define(version: 2026_03_24_100003) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -29,6 +29,20 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
     t.index ["provider_type", "provider_id"], name: "index_account_providers_on_provider_type_and_provider_id", unique: true
   end
 
+  create_table "account_shares", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
+    t.uuid "account_id", null: false
+    t.uuid "user_id", null: false
+    t.string "permission", default: "read_only", null: false
+    t.boolean "include_in_finances", default: true, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id", "user_id"], name: "index_account_shares_on_account_id_and_user_id", unique: true
+    t.index ["account_id"], name: "index_account_shares_on_account_id"
+    t.index ["user_id", "include_in_finances"], name: "index_account_shares_on_user_id_and_include_in_finances"
+    t.index ["user_id"], name: "index_account_shares_on_user_id"
+    t.check_constraint "permission::text = ANY (ARRAY['full_control'::character varying, 'read_write'::character varying, 'read_only'::character varying]::text[])", name: "chk_account_shares_permission"
+  end
+
   create_table "accounts", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
     t.string "subtype"
     t.uuid "family_id", null: false
@@ -49,6 +63,9 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
     t.string "institution_name"
     t.string "institution_domain"
     t.text "notes"
+    t.jsonb "holdings_snapshot_data"
+    t.datetime "holdings_snapshot_at"
+    t.uuid "owner_id"
     t.index ["accountable_id", "accountable_type"], name: "index_accounts_on_accountable_id_and_accountable_type"
     t.index ["accountable_type"], name: "index_accounts_on_accountable_type"
     t.index ["currency"], name: "index_accounts_on_currency"
@@ -58,6 +75,7 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
     t.index ["family_id", "status"], name: "index_accounts_on_family_id_and_status"
     t.index ["family_id"], name: "index_accounts_on_family_id"
     t.index ["import_id"], name: "index_accounts_on_import_id"
+    t.index ["owner_id"], name: "index_accounts_on_owner_id"
     t.index ["plaid_account_id"], name: "index_accounts_on_plaid_account_id"
     t.index ["simplefin_account_id"], name: "index_accounts_on_simplefin_account_id"
     t.index ["status"], name: "index_accounts_on_status"
@@ -516,6 +534,8 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
     t.string "vector_store_id"
     t.string "moniker", default: "Family", null: false
     t.string "assistant_type", default: "builtin", null: false
+    t.string "default_account_sharing", default: "shared", null: false
+    t.check_constraint "default_account_sharing::text = ANY (ARRAY['shared'::character varying, 'private'::character varying]::text[])", name: "chk_families_default_account_sharing"
     t.check_constraint "month_start_day >= 1 AND month_start_day <= 28", name: "month_start_day_range"
   end
 
@@ -705,8 +725,8 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
     t.date "sync_start_date"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.index ["indexa_capital_item_id", "indexa_capital_account_id"], name: "index_indexa_capital_accounts_on_item_and_account_id", unique: true, where: "(indexa_capital_account_id IS NOT NULL)"
     t.index ["indexa_capital_authorization_id"], name: "idx_on_indexa_capital_authorization_id_58db208d52"
+    t.index ["indexa_capital_item_id", "indexa_capital_account_id"], name: "index_indexa_capital_accounts_on_item_and_account_id", unique: true, where: "(indexa_capital_account_id IS NOT NULL)"
     t.index ["indexa_capital_item_id"], name: "index_indexa_capital_accounts_on_indexa_capital_item_id"
   end
 
@@ -1497,10 +1517,13 @@ ActiveRecord::Schema[7.2].define(version: 2026_03_20_080659) do
   end
 
   add_foreign_key "account_providers", "accounts", on_delete: :cascade
+  add_foreign_key "account_shares", "accounts"
+  add_foreign_key "account_shares", "users"
   add_foreign_key "accounts", "families"
   add_foreign_key "accounts", "imports"
   add_foreign_key "accounts", "plaid_accounts"
   add_foreign_key "accounts", "simplefin_accounts"
+  add_foreign_key "accounts", "users", column: "owner_id", on_delete: :nullify
   add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
   add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
   add_foreign_key "api_keys", "users"
diff --git a/test/controllers/impersonation_sessions_controller_test.rb b/test/controllers/impersonation_sessions_controller_test.rb
index 7adda7b74..7dce7f5ac 100644
--- a/test/controllers/impersonation_sessions_controller_test.rb
+++ b/test/controllers/impersonation_sessions_controller_test.rb
@@ -11,7 +11,7 @@ class ImpersonationSessionsControllerTest < ActionDispatch::IntegrationTest
 
     assert_difference "impersonator_session.logs.count", 2 do
       get root_path
-      get account_path(impersonated.family.accounts.first)
+      get account_path(impersonated.accessible_accounts.first)
     end
   end
 
diff --git a/test/controllers/transactions_controller_test.rb b/test/controllers/transactions_controller_test.rb
index f3faea941..fdc9ce851 100644
--- a/test/controllers/transactions_controller_test.rb
+++ b/test/controllers/transactions_controller_test.rb
@@ -162,7 +162,7 @@ end
       income_money: Money.new(0, "USD")
     )
 
-    Transaction::Search.expects(:new).with(family, filters: {}).returns(search)
+    Transaction::Search.expects(:new).with(family, filters: {}, accessible_account_ids: [ account.id ]).returns(search)
     search.expects(:totals).once.returns(totals)
 
     get transactions_url
@@ -184,7 +184,7 @@ end
       income_money: Money.new(0, "USD")
     )
 
-    Transaction::Search.expects(:new).with(family, filters: { "categories" => [ "Food" ], "types" => [ "expense" ] }).returns(search)
+    Transaction::Search.expects(:new).with(family, filters: { "categories" => [ "Food" ], "types" => [ "expense" ] }, accessible_account_ids: [ account.id ]).returns(search)
     search.expects(:totals).once.returns(totals)
 
     get transactions_url(q: { categories: [ "Food" ], types: [ "expense" ] })
diff --git a/test/fixtures/account_shares.yml b/test/fixtures/account_shares.yml
new file mode 100644
index 000000000..200af469d
--- /dev/null
+++ b/test/fixtures/account_shares.yml
@@ -0,0 +1,13 @@
+# Share the checking account with family_member (full control)
+depository_shared_with_member:
+  account: depository
+  user: family_member
+  permission: full_control
+  include_in_finances: true
+
+# Share the credit card with family_member (read only)
+credit_card_shared_with_member:
+  account: credit_card
+  user: family_member
+  permission: read_only
+  include_in_finances: true
diff --git a/test/fixtures/accounts.yml b/test/fixtures/accounts.yml
index 3b0354d39..e2554e5dc 100644
--- a/test/fixtures/accounts.yml
+++ b/test/fixtures/accounts.yml
@@ -1,5 +1,6 @@
 other_asset:
   family: dylan_family
+  owner: family_admin
   name: Collectable Account
   balance: 550
   currency: USD
@@ -9,6 +10,7 @@ other_asset:
 
 other_liability:
   family: dylan_family
+  owner: family_admin
   name: IOU (personal debt to friend)
   balance: 200
   currency: USD
@@ -18,6 +20,7 @@ other_liability:
 
 depository:
   family: dylan_family
+  owner: family_admin
   name: Checking Account
   balance: 5000
   currency: USD
@@ -27,6 +30,7 @@ depository:
 
 connected:
   family: dylan_family
+  owner: family_admin
   name: Plaid Depository Account
   balance: 5000
   currency: USD
@@ -37,6 +41,7 @@ connected:
 
 credit_card:
   family: dylan_family
+  owner: family_admin
   name: Credit Card
   balance: 1000
   currency: USD
@@ -46,6 +51,7 @@ credit_card:
 
 investment:
   family: dylan_family
+  owner: family_admin
   name: Robinhood Brokerage Account
   balance: 10000
   cash_balance: 5000
@@ -56,6 +62,7 @@ investment:
 
 loan:
   family: dylan_family
+  owner: family_admin
   name: Mortgage Loan
   balance: 500000
   currency: USD
@@ -65,6 +72,7 @@ loan:
 
 property:
   family: dylan_family
+  owner: family_admin
   name: 123 Maybe Court
   balance: 550000
   currency: USD
@@ -74,6 +82,7 @@ property:
 
 vehicle:
   family: dylan_family
+  owner: family_admin
   name: Honda Accord
   balance: 18000
   currency: USD
@@ -83,6 +92,7 @@ vehicle:
 
 crypto:
   family: dylan_family
+  owner: family_admin
   name: Bitcoin
   balance: 10000
   currency: USD
diff --git a/test/models/account_share_test.rb b/test/models/account_share_test.rb
new file mode 100644
index 000000000..99763ae53
--- /dev/null
+++ b/test/models/account_share_test.rb
@@ -0,0 +1,61 @@
+require "test_helper"
+
+class AccountShareTest < ActiveSupport::TestCase
+  setup do
+    @admin = users(:family_admin)
+    @member = users(:family_member)
+    @account = accounts(:depository)
+  end
+
+  test "valid share" do
+    # Use an account that doesn't already have a share with member
+    account = accounts(:investment)
+    account.account_shares.where(user: @member).destroy_all
+    share = AccountShare.new(account: account, user: @member, permission: "read_only")
+    assert share.valid?
+  end
+
+  test "invalid permission" do
+    share = AccountShare.new(account: @account, user: @member, permission: "invalid")
+    assert_not share.valid?
+    assert_includes share.errors[:permission], "is not included in the list"
+  end
+
+  test "cannot share with account owner" do
+    share = AccountShare.new(account: @account, user: @admin, permission: "read_only")
+    assert_not share.valid?
+    assert_includes share.errors[:user], "is already the owner of this account"
+  end
+
+  test "cannot duplicate share for same user and account" do
+    # depository already shared with member via fixture
+    duplicate = AccountShare.new(account: @account, user: @member, permission: "read_only")
+    assert_not duplicate.valid?
+  end
+
+  test "permission helper methods" do
+    share = AccountShare.new(permission: "full_control")
+    assert share.full_control?
+    assert_not share.read_write?
+    assert_not share.read_only?
+    assert share.can_annotate?
+    assert share.can_edit?
+
+    share.permission = "read_write"
+    assert share.read_write?
+    assert share.can_annotate?
+    assert_not share.can_edit?
+
+    share.permission = "read_only"
+    assert share.read_only?
+    assert_not share.can_annotate?
+    assert_not share.can_edit?
+  end
+
+  test "cannot share with user from different family" do
+    other_user = users(:empty)
+    share = AccountShare.new(account: @account, user: other_user, permission: "read_only")
+    assert_not share.valid?
+    assert_includes share.errors[:user], "must be in the same family"
+  end
+end
diff --git a/test/models/account_test.rb b/test/models/account_test.rb
index a8284d3db..c1daf738a 100644
--- a/test/models/account_test.rb
+++ b/test/models/account_test.rb
@@ -6,6 +6,8 @@ class AccountTest < ActiveSupport::TestCase
   setup do
     @account = @syncable = accounts(:depository)
     @family = families(:dylan_family)
+    @admin = users(:family_admin)
+    @member = users(:family_member)
   end
 
   test "can destroy" do
@@ -19,6 +21,7 @@ class AccountTest < ActiveSupport::TestCase
 
     account = Account.create_and_sync({
       family: @family,
+      owner: @admin,
       name: "Test Account",
       balance: 100,
       currency: "USD",
@@ -37,6 +40,7 @@ class AccountTest < ActiveSupport::TestCase
     account = Account.create_and_sync(
       {
         family: @family,
+        owner: @admin,
         name: "Linked Account",
         balance: 500,
         currency: "EUR",
@@ -57,6 +61,7 @@ class AccountTest < ActiveSupport::TestCase
     account = Account.create_and_sync(
       {
         family: @family,
+        owner: @admin,
         name: "Test Account",
         balance: 1000,
         currency: "GBP",
@@ -79,6 +84,7 @@ class AccountTest < ActiveSupport::TestCase
     account = Account.create_and_sync(
       {
         family: @family,
+        owner: @admin,
         name: "Test Account",
         balance: 1000,
         currency: "USD",
@@ -96,6 +102,7 @@ class AccountTest < ActiveSupport::TestCase
   test "gets short/long subtype label" do
     investment = Investment.new(subtype: "hsa")
     account = @family.accounts.create!(
+      owner: @admin,
       name: "Test Investment",
       balance: 1000,
       currency: "USD",
@@ -116,6 +123,7 @@ class AccountTest < ActiveSupport::TestCase
   test "tax_treatment delegates to accountable for Investment" do
     investment = Investment.new(subtype: "401k")
     account = @family.accounts.create!(
+      owner: @admin,
       name: "Test 401k",
       balance: 1000,
       currency: "USD",
@@ -129,6 +137,7 @@ class AccountTest < ActiveSupport::TestCase
   test "tax_treatment delegates to accountable for Crypto" do
     crypto = Crypto.new(tax_treatment: :taxable)
     account = @family.accounts.create!(
+      owner: @admin,
       name: "Test Crypto",
       balance: 500,
       currency: "USD",
@@ -148,6 +157,7 @@ class AccountTest < ActiveSupport::TestCase
   test "tax_advantaged? returns true for tax-advantaged accounts" do
     investment = Investment.new(subtype: "401k")
     account = @family.accounts.create!(
+      owner: @admin,
       name: "Test 401k",
       balance: 1000,
       currency: "USD",
@@ -161,6 +171,7 @@ class AccountTest < ActiveSupport::TestCase
   test "tax_advantaged? returns false for taxable accounts" do
     investment = Investment.new(subtype: "brokerage")
     account = @family.accounts.create!(
+      owner: @admin,
       name: "Test Brokerage",
       balance: 1000,
       currency: "USD",
@@ -193,4 +204,86 @@ class AccountTest < ActiveSupport::TestCase
 
     assert_not ActiveStorage::Attachment.exists?(attachment_id)
   end
+
+  # Account sharing tests
+
+  test "owned_by? returns true for account owner" do
+    assert @account.owned_by?(@admin)
+    assert_not @account.owned_by?(@member)
+  end
+
+  test "shared_with? returns true for owner and shared users" do
+    assert @account.shared_with?(@admin) # owner
+    # depository already shared with member via fixture
+    assert @account.shared_with?(@member)
+  end
+
+  test "shared? returns true when account has shares" do
+    account = accounts(:investment)
+    account.account_shares.destroy_all
+    assert_not account.shared?
+
+    account.share_with!(@member, permission: "read_only")
+    assert account.shared?
+  end
+
+  test "permission_for returns correct permission level" do
+    assert_equal :owner, @account.permission_for(@admin)
+
+    # depository already shared with member via fixture
+    share = @account.account_shares.find_by(user: @member)
+    share.update!(permission: "read_write")
+    assert_equal :read_write, @account.permission_for(@member)
+  end
+
+  test "accessible_by scope returns owned and shared accounts" do
+    # Clear existing shares for clean test
+    AccountShare.delete_all
+
+    admin_accessible = @family.accounts.accessible_by(@admin)
+    member_accessible = @family.accounts.accessible_by(@member)
+
+    # Admin owns all fixture accounts
+    assert_equal @family.accounts.count, admin_accessible.count
+    # Member has no access (no shares, no owned accounts)
+    assert_equal 0, member_accessible.count
+
+    # Share one account
+    @account.share_with!(@member, permission: "read_only")
+    member_accessible = @family.accounts.accessible_by(@member)
+    assert_equal 1, member_accessible.count
+    assert_includes member_accessible, @account
+  end
+
+  test "included_in_finances_for scope respects include_in_finances flag" do
+    AccountShare.delete_all
+
+    @account.share_with!(@member, permission: "read_only", include_in_finances: true)
+    assert_includes @family.accounts.included_in_finances_for(@member), @account
+
+    share = @account.account_shares.find_by(user: @member)
+    share.update!(include_in_finances: false)
+    assert_not_includes @family.accounts.included_in_finances_for(@member), @account
+  end
+
+  test "auto_share_with_family creates shares for all non-owner members" do
+    account = Account.create_and_sync({
+      family: @family,
+      owner: @admin,
+      name: "New Shared Account",
+      balance: 100,
+      currency: "USD",
+      accountable_type: "Depository",
+      accountable_attributes: {}
+    })
+
+    assert_difference -> { AccountShare.count }, @family.users.where.not(id: @admin.id).count do
+      account.auto_share_with_family!
+    end
+
+    share = account.account_shares.find_by(user: @member)
+    assert_not_nil share
+    assert_equal "read_write", share.permission
+    assert share.include_in_finances?
+  end
 end