diff --git a/app/controllers/api/v1/base_controller.rb b/app/controllers/api/v1/base_controller.rb
index f1631ec1c..1a8dff77f 100644
--- a/app/controllers/api/v1/base_controller.rb
+++ b/app/controllers/api/v1/base_controller.rb
@@ -335,4 +335,12 @@ class Api::V1::BaseController < ApplicationController
         render_json({ error: "feature_disabled", message: "AI features are not enabled for this user" }, status: :forbidden)
       end
     end
+
+    # Check if a Family feature module is enabled. Mirrors `require_ai_enabled`.
+    # See docs/feature-gating.md for the three-tier gating model.
+    def require_module!(name)
+      family = Current.family || current_resource_owner&.family
+      return if family&.module_enabled?(name)
+      render_json({ error: "feature_disabled", message: "Feature module '#{name}' is disabled for this family" }, status: :forbidden)
+    end
 end
diff --git a/app/controllers/api/v1/holdings_controller.rb b/app/controllers/api/v1/holdings_controller.rb
index 7f08dfe3b..4be295c27 100644
--- a/app/controllers/api/v1/holdings_controller.rb
+++ b/app/controllers/api/v1/holdings_controller.rb
@@ -3,6 +3,7 @@
 class Api::V1::HoldingsController < Api::V1::BaseController
   include Pagy::Backend
 
+  before_action -> { require_module!(:investments) }
   before_action :ensure_read_scope
   before_action :set_holding, only: [ :show ]
 
diff --git a/app/controllers/api/v1/securities_controller.rb b/app/controllers/api/v1/securities_controller.rb
index bc0715d10..f53845408 100644
--- a/app/controllers/api/v1/securities_controller.rb
+++ b/app/controllers/api/v1/securities_controller.rb
@@ -4,6 +4,7 @@ class Api::V1::SecuritiesController < Api::V1::BaseController
   include Pagy::Backend
   include Api::V1::SecurityResourceFiltering
 
+  before_action -> { require_module!(:investments) }
   before_action :ensure_read_scope
   before_action :set_security, only: :show
 
diff --git a/app/controllers/api/v1/trades_controller.rb b/app/controllers/api/v1/trades_controller.rb
index 0538fe321..33638ef6b 100644
--- a/app/controllers/api/v1/trades_controller.rb
+++ b/app/controllers/api/v1/trades_controller.rb
@@ -3,6 +3,7 @@
 class Api::V1::TradesController < Api::V1::BaseController
   include Pagy::Backend
 
+  before_action -> { require_module!(:investments) }
   before_action :ensure_read_scope, only: [ :index, :show ]
   before_action :ensure_write_scope, only: [ :create, :update, :destroy ]
   before_action :set_trade, only: [ :show, :update, :destroy ]
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 7306d504f..c663df392 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -2,7 +2,7 @@ class ApplicationController < ActionController::Base
   include RestoreLayoutPreferences, Onboardable, Localize, AutoSync, Authentication, Invitable,
           SelfHostable, StoreLocation, Impersonatable, Breadcrumbable,
           FeatureGuardable, Notifiable, SafePagination, AccountAuthorizable,
-          PreviewGateable
+          PreviewGateable, ModuleGateable
   include Pundit::Authorization
 
   include Pagy::Backend
diff --git a/app/controllers/concerns/module_gateable.rb b/app/controllers/concerns/module_gateable.rb
new file mode 100644
index 000000000..347b5e3a0
--- /dev/null
+++ b/app/controllers/concerns/module_gateable.rb
@@ -0,0 +1,25 @@
+module ModuleGateable
+  extend ActiveSupport::Concern
+
+  included do
+    helper_method :module_enabled?
+  end
+
+  class_methods do
+    def require_module!(name)
+      before_action -> { enforce_module!(name) }
+    end
+  end
+
+  def module_enabled?(name)
+    family = Current.family
+    return true if family.nil?
+    family.module_enabled?(name)
+  end
+
+  private
+    def enforce_module!(name)
+      return if module_enabled?(name)
+      redirect_to root_path, alert: I18n.t("modules.not_enabled")
+    end
+end
diff --git a/app/controllers/holdings_controller.rb b/app/controllers/holdings_controller.rb
index 45a89f938..158b6d717 100644
--- a/app/controllers/holdings_controller.rb
+++ b/app/controllers/holdings_controller.rb
@@ -1,6 +1,8 @@
 class HoldingsController < ApplicationController
   include StreamExtensions
 
+  require_module! :investments
+
   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 sync_prices]
 
diff --git a/app/controllers/investments_controller.rb b/app/controllers/investments_controller.rb
index 5fa25f123..8615e58f8 100644
--- a/app/controllers/investments_controller.rb
+++ b/app/controllers/investments_controller.rb
@@ -1,5 +1,7 @@
 class InvestmentsController < ApplicationController
   include AccountableResource
 
+  require_module! :investments
+
   permitted_accountable_attributes :id, :subtype
 end
diff --git a/app/controllers/securities_controller.rb b/app/controllers/securities_controller.rb
index f369c33c5..ec5c98f98 100644
--- a/app/controllers/securities_controller.rb
+++ b/app/controllers/securities_controller.rb
@@ -1,4 +1,6 @@
 class SecuritiesController < ApplicationController
+  require_module! :investments
+
   def index
     @securities = Security.search_provider(
       params[:q],
diff --git a/app/controllers/settings/preferences_controller.rb b/app/controllers/settings/preferences_controller.rb
index 5798c573e..5863a3f18 100644
--- a/app/controllers/settings/preferences_controller.rb
+++ b/app/controllers/settings/preferences_controller.rb
@@ -3,17 +3,18 @@ class Settings::PreferencesController < ApplicationController
 
   def show
     @user = Current.user
+    @family = Current.family
   end
 
   # Writes per-user boolean preferences stored in the JSONB `users.preferences`
-  # column. Mirrors Settings::AppearancesController#update so the toggle card on
-  # the Preferences page can submit directly without going through the broader
-  # UsersController#update flow (which expects a full user form payload).
+  # column, plus per-family module toggles in `families.disabled_modules`. The
+  # auto-submit pattern matches Settings::AppearancesController#update.
   def update
     @user = Current.user
     user_params = params.permit(user: [ :preview_features_enabled ]).fetch(:user, {})
+    module_params = params.permit(family: { modules: {} }).dig(:family, :modules)
 
-    @user.transaction do
+    ActiveRecord::Base.transaction do
       @user.lock!
       updated_prefs = (@user.preferences || {}).deep_dup
       if user_params.key?(:preview_features_enabled)
@@ -21,6 +22,22 @@ class Settings::PreferencesController < ApplicationController
           ActiveModel::Type::Boolean.new.cast(user_params[:preview_features_enabled])
       end
       @user.update!(preferences: updated_prefs)
+
+      if module_params.present?
+        family = Current.family
+        family.lock!
+        disabled = Array(family.disabled_modules).map(&:to_s)
+        module_params.each do |name, enabled|
+          name = name.to_s
+          next unless Family::AVAILABLE_MODULES.include?(name)
+          if ActiveModel::Type::Boolean.new.cast(enabled)
+            disabled.delete(name)
+          else
+            disabled << name unless disabled.include?(name)
+          end
+        end
+        family.update!(disabled_modules: disabled)
+      end
     end
     redirect_to settings_preferences_path
   end
diff --git a/app/controllers/trades_controller.rb b/app/controllers/trades_controller.rb
index e3a90121e..e7da4e657 100644
--- a/app/controllers/trades_controller.rb
+++ b/app/controllers/trades_controller.rb
@@ -1,6 +1,8 @@
 class TradesController < ApplicationController
   include EntryableResource
 
+  require_module! :investments
+
   before_action :set_entry_for_unlock, only: :unlock
 
   # Defaults to a buy trade
diff --git a/app/helpers/navigation_helper.rb b/app/helpers/navigation_helper.rb
new file mode 100644
index 000000000..a2b5c7e2d
--- /dev/null
+++ b/app/helpers/navigation_helper.rb
@@ -0,0 +1,31 @@
+module NavigationHelper
+  def main_nav_items(intro_mode:)
+    return intro_nav_items if intro_mode
+
+    items = [
+      { name: t("layouts.application.nav.home"), path: root_path, icon: "pie-chart", icon_custom: false, active: page_active?(root_path) },
+      { name: t("layouts.application.nav.transactions"), path: transactions_path, icon: "credit-card", icon_custom: false, active: page_active?(transactions_path) },
+      { name: t("layouts.application.nav.reports"), path: reports_path, icon: "chart-bar", icon_custom: false, active: page_active?(reports_path) },
+      { name: t("layouts.application.nav.budgets"), path: budgets_path, icon: "map", icon_custom: false, active: page_active?(budgets_path) },
+      { name: t("layouts.application.nav.assistant"), path: chats_path, icon: "icon-assistant", icon_custom: true, active: page_active?(chats_path), mobile_only: true }
+    ]
+
+    items.reject { |item| item[:module] && !module_enabled?(item[:module]) }
+  end
+
+  def mobile_nav_items(intro_mode:)
+    main_nav_items(intro_mode: intro_mode)
+  end
+
+  def desktop_nav_items(intro_mode:)
+    main_nav_items(intro_mode: intro_mode).reject { |item| item[:mobile_only] }
+  end
+
+  private
+    def intro_nav_items
+      [
+        { name: t("layouts.application.nav.home"), path: chats_path, icon: "home", icon_custom: false, active: page_active?(chats_path) },
+        { name: "Intro", path: intro_path, icon: "sparkles", icon_custom: false, active: page_active?(intro_path) }
+      ]
+    end
+end
diff --git a/app/models/family.rb b/app/models/family.rb
index 3ebd72406..c652c682a 100644
--- a/app/models/family.rb
+++ b/app/models/family.rb
@@ -21,6 +21,7 @@ class Family < ApplicationRecord
   MONIKERS = [ "Family", "Group" ].freeze
   ASSISTANT_TYPES = %w[builtin external].freeze
   SHARING_DEFAULTS = %w[shared private].freeze
+  AVAILABLE_MODULES = %w[investments].freeze
 
   has_many :users, dependent: :destroy
   has_many :accounts, dependent: :destroy
@@ -55,6 +56,10 @@ class Family < ApplicationRecord
 
   before_validation :normalize_enabled_currencies!
 
+  def module_enabled?(name)
+    Array(disabled_modules).exclude?(name.to_s)
+  end
+
   def primary_currency_code
     normalize_currency_code(currency) || "USD"
   end
diff --git a/app/views/accounts/new.html.erb b/app/views/accounts/new.html.erb
index 7caa4dda3..07939edea 100644
--- a/app/views/accounts/new.html.erb
+++ b/app/views/accounts/new.html.erb
@@ -5,8 +5,10 @@
        <% end %>>
     <% unless params[:classification] == "liability" %>
       <%= render "account_type", accountable: Depository.new %>
-      <%= render "account_type", accountable: Investment.new %>
-      <%= render "account_type", accountable: Crypto.new %>
+      <% if module_enabled?(:investments) %>
+        <%= render "account_type", accountable: Investment.new %>
+        <%= render "account_type", accountable: Crypto.new %>
+      <% end %>
       <%= render "account_type", accountable: Property.new %>
       <%= render "account_type", accountable: Vehicle.new %>
     <% end %>
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index cffcc2c7f..bbbecc09a 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -1,21 +1,7 @@
 <% intro_mode = Current.user&.ui_layout_intro? %>
 <% home_path = intro_mode ? chats_path : root_path %>
-<% mobile_nav_items = if intro_mode
-  [
-    { name: t(".nav.home"), path: chats_path, icon: "home", icon_custom: false, active: page_active?(chats_path) },
-    { name: "Intro", path: intro_path, icon: "sparkles", icon_custom: false, active: page_active?(intro_path) }
-  ]
-else
-  [
-    { name: t(".nav.home"), path: root_path, icon: "pie-chart", icon_custom: false, active: page_active?(root_path) },
-    { name: t(".nav.transactions"), path: transactions_path, icon: "credit-card", icon_custom: false, active: page_active?(transactions_path) },
-    { name: t(".nav.reports"), path: reports_path, icon: "chart-bar", icon_custom: false, active: page_active?(reports_path) },
-    { name: t(".nav.budgets"), path: budgets_path, icon: "map", icon_custom: false, active: page_active?(budgets_path) },
-    { name: t(".nav.assistant"), path: chats_path, icon: "icon-assistant", icon_custom: true, active: page_active?(chats_path), mobile_only: true }
-  ]
-end %>
-
-<% desktop_nav_items = mobile_nav_items.reject { |item| item[:mobile_only] } %>
+<% mobile_nav_items = mobile_nav_items(intro_mode: intro_mode) %>
+<% desktop_nav_items = desktop_nav_items(intro_mode: intro_mode) %>
 <% expanded_sidebar_class = "w-full" %>
 <% collapsed_sidebar_class = "w-0 overflow-hidden" %>
 
diff --git a/app/views/settings/preferences/show.html.erb b/app/views/settings/preferences/show.html.erb
index 80b767bd1..c1f285051 100644
--- a/app/views/settings/preferences/show.html.erb
+++ b/app/views/settings/preferences/show.html.erb
@@ -227,3 +227,34 @@
     </label>
   <% end %>
 </section>
+
+<%# Family feature modules. One toggle per entry in Family::AVAILABLE_MODULES.
+    Stored as opt-out strings in families.disabled_modules; default state is
+    enabled so existing families see no change. See docs/feature-gating.md. %>
+<section class="bg-container shadow-border-xs rounded-xl p-4 space-y-4">
+  <div class="text-sm space-y-1">
+    <h4 class="text-primary"><%= t(".modules.title") %></h4>
+    <p class="text-secondary"><%= t(".modules.description") %></p>
+  </div>
+
+  <%= form_with url: settings_preferences_path, method: :patch,
+        data: { controller: "auto-submit-form" } do |f| %>
+    <div class="space-y-3">
+      <% Family::AVAILABLE_MODULES.each do |module_name| %>
+        <label for="family_modules_<%= module_name %>" class="flex cursor-pointer items-center gap-4 justify-between">
+          <div class="text-sm space-y-1">
+            <h5 class="text-primary"><%= t("modules.#{module_name}.title") %></h5>
+            <p class="text-secondary"><%= t("modules.#{module_name}.description") %></p>
+          </div>
+          <%= hidden_field_tag "family[modules][#{module_name}]", "0" %>
+          <%= render DS::Toggle.new(
+                id: "family_modules_#{module_name}",
+                name: "family[modules][#{module_name}]",
+                checked: @family.module_enabled?(module_name),
+                data: { auto_submit_form_target: "auto" }
+          ) %>
+        </label>
+      <% end %>
+    </div>
+  <% end %>
+</section>
diff --git a/config/locales/views/modules/en.yml b/config/locales/views/modules/en.yml
new file mode 100644
index 000000000..0b974b94e
--- /dev/null
+++ b/config/locales/views/modules/en.yml
@@ -0,0 +1,6 @@
+en:
+  modules:
+    not_enabled: This feature module is disabled. Re-enable it in Settings → Preferences.
+    investments:
+      title: Investments
+      description: Track holdings, trades, and investment/crypto accounts. Disabling hides the entire investments surface; existing data is preserved.
diff --git a/config/locales/views/settings/en.yml b/config/locales/views/settings/en.yml
index e7abc768f..1aac2db39 100644
--- a/config/locales/views/settings/en.yml
+++ b/config/locales/views/settings/en.yml
@@ -157,6 +157,9 @@ en:
         preview:
           title: Enable preview features
           description: Opt in to in-progress features tagged preview or canary.
+        modules:
+          title: Feature modules
+          description: Turn whole feature verticals on or off. Existing data is preserved; toggling back on restores everything.
     profiles:
       destroy:
         cannot_remove_self: You cannot remove yourself from the account.
diff --git a/db/migrate/20260522120000_add_disabled_modules_to_families.rb b/db/migrate/20260522120000_add_disabled_modules_to_families.rb
new file mode 100644
index 000000000..8c72b3e5d
--- /dev/null
+++ b/db/migrate/20260522120000_add_disabled_modules_to_families.rb
@@ -0,0 +1,5 @@
+class AddDisabledModulesToFamilies < ActiveRecord::Migration[7.2]
+  def change
+    add_column :families, :disabled_modules, :string, array: true, null: false, default: []
+  end
+end
diff --git a/docs/feature-gating.md b/docs/feature-gating.md
new file mode 100644
index 000000000..d793608ee
--- /dev/null
+++ b/docs/feature-gating.md
@@ -0,0 +1,109 @@
+# Feature Gating
+
+Sure already has three layered mechanisms for turning features on and off. Use them. Do not introduce a new framework (no Flipper, no plugin loader, no `app/modules/*/` autoload tree).
+
+## The three gating tiers
+
+| Tier | Where | When to use | Precedent |
+|------|-------|-------------|-----------|
+| **Instance** | `Rails.application.config.app_mode` (`config/application.rb`) + env vars like `SIMPLEFIN_INCLUDE_PENDING` | Whole-deploy switches: managed vs self-hosted, opt-in integrations that require credentials. | `app_mode.self_hosted?`, `Rails.configuration.x.simplefin.*` |
+| **Per-user** | `User#preferences` jsonb | Personal preferences that affect only that user's UI. | `User#preview_features_enabled?` (`app/models/user.rb`), `User#ai_enabled?` |
+| **Per-family ("modules")** | `Family#disabled_modules` text[] + `Family#module_enabled?(:name)` | Toggling whole feature verticals (Investments, future: Budgets, Goals, AI). Affects everyone in the family. | `Family#recurring_transactions_disabled?` (existing), `Family#module_enabled?(:investments)` (this doc) |
+
+## The "module" rule
+
+A module is just a string in `families.disabled_modules`. It opts a feature vertical OUT — default is enabled, presence in the array means disabled. Backwards-compatible: existing families ship with `[]` and see no change.
+
+```ruby
+family.module_enabled?(:investments) # => true (default)
+family.update!(disabled_modules: ["investments"])
+family.module_enabled?(:investments) # => false
+```
+
+No migrations per module. Add an entry to `Family::AVAILABLE_MODULES` and wire the three enforcement layers below.
+
+## Three enforcement layers — required for every module
+
+The biggest risk with feature gating is **half-enforcement**: hiding the UI but leaving controllers, jobs, or model writes open. A user disables the module, the surface disappears, background jobs keep writing data, and re-enabling produces surprise state. **For every module, all three layers must call `Family#module_enabled?`.**
+
+### 1. View / nav
+
+Inside ERB and helpers, call `module_enabled?(:investments)`. The method is provided as a `helper_method` by `ModuleGateable` (auto-included in `ApplicationController`).
+
+```erb
+<% if module_enabled?(:investments) %>
+  <%= render "account_type", accountable: Investment.new %>
+  <%= render "account_type", accountable: Crypto.new %>
+<% end %>
+```
+
+For nav items, opt in via the `module:` key in `NavigationHelper#main_nav_items`; disabled modules are filtered out and the bottom-mobile nav redistributes via `justify-around`. **Never auto-fill empty slots** with promoted sidebar items — empty slot is the affordance that the module is off.
+
+### 2. Controller
+
+HTML controllers use the `require_module!` class macro from `ModuleGateable`:
+
+```ruby
+class InvestmentsController < ApplicationController
+  require_module! :investments
+end
+```
+
+This redirects to `root_path` with `flash[:alert] = t("modules.not_enabled")` when the module is off.
+
+API controllers (under `Api::V1`) use the instance method on `Api::V1::BaseController`:
+
+```ruby
+class Api::V1::HoldingsController < Api::V1::BaseController
+  before_action -> { require_module!(:investments) }
+end
+```
+
+This renders `{ error: "feature_disabled" }` with status `403`. Matches the existing `require_ai_enabled` pattern.
+
+### 3. Background jobs / model writes
+
+If the module has scheduled jobs or model callbacks that write data, guard the entry point:
+
+```ruby
+class SomeInvestmentJob < ApplicationJob
+  def perform(family_id)
+    family = Family.find(family_id)
+    return unless family.module_enabled?(:investments)
+    # ...
+  end
+end
+```
+
+Without this, toggling off creates silent data accumulation, and toggling back on produces a populated module the user never approved.
+
+## Choosing the right tier
+
+- **Instance**: needs a deploy/restart. Right for integrations bound to env keys (Plaid, SimpleFIN, OpenAI), and for self-hosters who want a feature off at the docker-compose layer.
+- **Per-user**: right for opt-in/opt-out personal preferences that don't affect family-shared data (AI sidebar visibility, preview features, dark mode).
+- **Per-family module**: right for "we don't want this vertical at all" — affects all family members, the toggle lives in Settings → Preferences, and surfaces across web + API + jobs.
+
+If you find yourself wanting all three for one feature, you probably want per-family with a `Rails.configuration` instance kill-switch. Don't build "the module system" — there isn't one.
+
+## Naming and conventions
+
+- Module names are snake_case strings: `"investments"`, `"goals"`. Plural for verticals, singular for single features.
+- Add to `Family::AVAILABLE_MODULES` so the Settings UI picks them up.
+- Add locale entries under `modules.<name>.title` and `modules.<name>.description` in `config/locales/views/modules/<locale>.yml`.
+- Same string is used in `disabled_modules` array, controller `require_module!` arg, view `module_enabled?` arg, and locale key.
+
+## Not modules
+
+These are foundational primitives. They are not candidates for module gating because too much else FKs into them:
+
+- Account, Transaction, Entry, Trade, Valuation, Balance, Holding, Security
+- Category, Merchant, Transfer
+
+If you think one of these should be a module, you are wrong; redesign the feature instead.
+
+## What about a "modules registry"?
+
+Don't build one. Two reasons:
+
+1. You don't have three modules yet, and premature abstraction here is fatal because the surface is forever (per Discourse/WordPress prior art).
+2. `Family::AVAILABLE_MODULES` is the registry. It's an array. That's the framework.
diff --git a/test/models/family_test.rb b/test/models/family_test.rb
index f026ff6ab..0f9a9f736 100644
--- a/test/models/family_test.rb
+++ b/test/models/family_test.rb
@@ -234,4 +234,23 @@ class FamilyTest < ActiveSupport::TestCase
     assert_equal({ "type" => "financial_document" }, document.metadata)
     assert_equal "vs_test123", family.reload.vector_store_id
   end
+
+  test "module_enabled? defaults to true and toggles via disabled_modules" do
+    family = families(:dylan_family)
+
+    assert family.module_enabled?(:investments)
+    assert family.module_enabled?("investments")
+
+    family.update!(disabled_modules: [ "investments" ])
+    assert_not family.module_enabled?(:investments)
+    assert_not family.module_enabled?("investments")
+
+    family.update!(disabled_modules: [])
+    assert family.module_enabled?(:investments)
+  end
+
+  test "module_enabled? returns true for unknown modules (default-enabled)" do
+    family = families(:dylan_family)
+    assert family.module_enabled?(:nonexistent_module)
+  end
 end