diff --git a/app/helpers/organisation_helper.rb b/app/helpers/organisation_helper.rb
deleted file mode 100644
index 7c42bf358..000000000
--- a/app/helpers/organisation_helper.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-module OrganisationHelper
-  def organisation_header(path, user, current_organisation)
-    if path == "/organisations"
-      "Organisations"
-    elsif user.organisation_id == current_organisation.id
-      "Your organisation"
-    else
-      current_organisation.name
-    end
-  end
-
-  def organisation_name_row(user:, organisation:, summary_list:)
-    summary_list.row do |row|
-      row.key { "Name" }
-      row.value { organisation.name }
-      if user.support?
-        row.action(
-          visually_hidden_text: organisation.name.humanize.downcase,
-          href: edit_organisation_path(organisation),
-          html_attributes: { "data-qa": "change-#{organisation.name.downcase}" },
-        )
-      else
-        row.action
-      end
-    end
-  end
-end
diff --git a/app/helpers/organisations_helper.rb b/app/helpers/organisations_helper.rb
new file mode 100644
index 000000000..850742afc
--- /dev/null
+++ b/app/helpers/organisations_helper.rb
@@ -0,0 +1,40 @@
+module OrganisationsHelper
+  def organisation_header(path, user, current_organisation)
+    if path == "/organisations"
+      "Organisations"
+    elsif user.organisation_id == current_organisation.id
+      "Your organisation"
+    else
+      current_organisation.name
+    end
+  end
+
+  def display_organisation_attributes(organisation)
+    [
+      { name: "Organisation ID", value: "ORG#{organisation.id}", editable: false },
+      { name: "Address", value: organisation.address_string, editable: true },
+      { name: "Telephone number", value: organisation.phone, editable: true },
+      { name: "Type of provider", value: organisation.display_provider_type, editable: false },
+      { name: "Registration number", value: organisation.housing_registration_no || "", editable: false },
+      { name: "Rent periods", value: organisation.rent_period_labels, editable: false, format: :bullet },
+      { name: "Owns housing stock", value: organisation.holds_own_stock ? "Yes" : "No", editable: false },
+      { name: "Status", value: status_tag(organisation.status), editable: false },
+    ]
+  end
+
+  def organisation_name_row(user:, organisation:, summary_list:)
+    summary_list.row do |row|
+      row.key { "Name" }
+      row.value { organisation.name }
+      if user.support?
+        row.action(
+          visually_hidden_text: organisation.name.humanize.downcase,
+          href: edit_organisation_path(organisation),
+          html_attributes: { "data-qa": "change-#{organisation.name.downcase}" },
+        )
+      else
+        row.action
+      end
+    end
+  end
+end
diff --git a/app/helpers/tag_helper.rb b/app/helpers/tag_helper.rb
index 5a7498b78..e2a3ec92d 100644
--- a/app/helpers/tag_helper.rb
+++ b/app/helpers/tag_helper.rb
@@ -13,6 +13,7 @@ module TagHelper
     reactivating_soon: "Reactivating soon",
     deactivated: "Deactivated",
     deleted: "Deleted",
+    merged: "Merged",
   }.freeze
 
   COLOUR = {
@@ -27,6 +28,7 @@ module TagHelper
     reactivating_soon: "blue",
     deactivated: "grey",
     deleted: "red",
+    merged: "orange",
   }.freeze
 
   def status_tag(status, classes = [])
diff --git a/app/models/organisation.rb b/app/models/organisation.rb
index b4317c3e0..c050fef06 100644
--- a/app/models/organisation.rb
+++ b/app/models/organisation.rb
@@ -102,18 +102,6 @@ class Organisation < ApplicationRecord
     DISPLAY_PROVIDER_TYPE[provider_type.to_sym]
   end
 
-  def display_organisation_attributes
-    [
-      { name: "Organisation ID", value: "ORG#{id}", editable: false },
-      { name: "Address", value: address_string, editable: true },
-      { name: "Telephone number", value: phone, editable: true },
-      { name: "Type of provider", value: display_provider_type, editable: false },
-      { name: "Registration number", value: housing_registration_no || "", editable: false },
-      { name: "Rent periods", value: rent_period_labels, editable: false, format: :bullet },
-      { name: "Owns housing stock", value: holds_own_stock ? "Yes" : "No", editable: false },
-    ]
-  end
-
   def has_managing_agents?
     managing_agents.count.positive?
   end
@@ -121,4 +109,14 @@ class Organisation < ApplicationRecord
   def has_stock_owners?
     stock_owners.count.positive?
   end
+
+  def status
+    @status ||= status_at(Time.zone.now)
+  end
+
+  def status_at(date)
+    return :merged if merge_date.present? && merge_date < date
+
+    :active
+  end
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index f9e34a652..4e762c9a1 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -24,6 +24,7 @@ class User < ApplicationRecord
   after_validation :send_data_protection_confirmation_reminder, if: :is_dpo_changed?
 
   validates :organisation_id, presence: true
+  validate :organisation_not_merged
 
   has_paper_trail ignore: %w[last_sign_in_at
                              current_sign_in_at
@@ -185,6 +186,12 @@ protected
 
 private
 
+  def organisation_not_merged
+    if organisation&.merge_date.present? && organisation.merge_date < Time.zone.now
+      errors.add :organisation_id, I18n.t("validations.organisation.merged")
+    end
+  end
+
   def send_data_protection_confirmation_reminder
     return unless persisted?
     return unless is_dpo?
diff --git a/app/views/organisations/_organisation_list.html.erb b/app/views/organisations/_organisation_list.html.erb
index 389dff6b7..6a68433be 100644
--- a/app/views/organisations/_organisation_list.html.erb
+++ b/app/views/organisations/_organisation_list.html.erb
@@ -14,6 +14,9 @@
         <% row.cell(header: true, text: "Type", html_attributes: {
           scope: "col",
         }) %>
+        <% row.cell(header: true, text: "Status", html_attributes: {
+          scope: "col",
+        }) %>
       <% end %>
     <% end %>
     <% @organisations.each do |organisation| %>
@@ -26,6 +29,7 @@
           <% end %>
           <% row.cell(text: organisation.housing_registration_no) %>
           <% row.cell(text: organisation.display_provider_type) %>
+          <% row.cell(text: status_tag(organisation.status)) %>
         <% end %>
       <% end %>
     <% end %>
diff --git a/app/views/organisations/show.html.erb b/app/views/organisations/show.html.erb
index 87020120d..cc504c9f5 100644
--- a/app/views/organisations/show.html.erb
+++ b/app/views/organisations/show.html.erb
@@ -15,7 +15,7 @@
   <div class="govuk-grid-column-two-thirds-from-desktop">
     <%= govuk_summary_list do |summary_list| %>
       <%= organisation_name_row(user: current_user, organisation: @organisation, summary_list:) %>
-      <% @organisation.display_organisation_attributes.each do |attr| %>
+      <% display_organisation_attributes(@organisation).each do |attr| %>
         <% if can_edit_org?(current_user) && attr[:editable] %>
           <%= summary_list.row do |row| %>
             <% row.key { attr[:name] } %>
diff --git a/config/locales/en.yml b/config/locales/en.yml
index f4d968d44..07142821d 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -198,6 +198,7 @@ en:
       managing_agent:
         blank: "You must choose a managing agent"
         already_added: "You have already added this managing agent"
+      merged: "That organisation has already been merged. Select a different organisation."
     not_answered: "You must answer %{question}"
     invalid_option: "Enter a valid value for %{question}"
     invalid_number: "Enter a number for %{question}"
diff --git a/db/migrate/20230718151955_add_merge_date_to_organisation.rb b/db/migrate/20230718151955_add_merge_date_to_organisation.rb
new file mode 100644
index 000000000..7a7bac420
--- /dev/null
+++ b/db/migrate/20230718151955_add_merge_date_to_organisation.rb
@@ -0,0 +1,5 @@
+class AddMergeDateToOrganisation < ActiveRecord::Migration[7.0]
+  def change
+    add_column :organisations, :merge_date, :datetime
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 81d233874..75282b2bd 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[7.0].define(version: 2023_07_13_140231) do
+ActiveRecord::Schema[7.0].define(version: 2023_07_18_151955) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -192,14 +192,14 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.integer "hb"
     t.integer "hbrentshortfall"
     t.integer "property_relet"
-    t.datetime "mrcdate", precision: nil
+    t.datetime "mrcdate"
     t.integer "incref"
-    t.datetime "startdate", precision: nil
+    t.datetime "startdate"
     t.integer "armedforces"
     t.integer "first_time_property_let_as_social_housing"
     t.integer "unitletas"
     t.integer "builtype"
-    t.datetime "voiddate", precision: nil
+    t.datetime "voiddate"
     t.bigint "owning_organisation_id"
     t.bigint "managing_organisation_id"
     t.integer "renttype"
@@ -347,7 +347,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.string "old_id"
     t.string "old_visible_id"
     t.string "mobility_type"
-    t.datetime "startdate", precision: nil
+    t.datetime "startdate"
     t.string "location_admin_district"
     t.boolean "confirmed"
     t.index ["old_id"], name: "index_locations_on_old_id", unique: true
@@ -433,6 +433,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.integer "unspecified_units"
     t.string "old_org_id"
     t.string "old_visible_id"
+    t.datetime "merge_date"
     t.index ["old_visible_id"], name: "index_organisations_on_old_visible_id", unique: true
   end
 
@@ -518,7 +519,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.integer "stairbought"
     t.integer "stairowned"
     t.decimal "mrent", precision: 10, scale: 2
-    t.datetime "exdate", precision: nil
+    t.datetime "exdate"
     t.integer "exday"
     t.integer "exmonth"
     t.integer "exyear"
@@ -554,7 +555,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.integer "wchair"
     t.integer "income2_value_check"
     t.integer "armedforcesspouse"
-    t.datetime "hodate", precision: nil
+    t.datetime "hodate"
     t.integer "hoday"
     t.integer "homonth"
     t.integer "hoyear"
@@ -607,9 +608,9 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.integer "discounted_sale_value_check"
     t.integer "student_not_child_value_check"
     t.integer "percentage_discount_value_check"
+    t.integer "combined_income_value_check"
     t.integer "buyer_livein_value_check"
     t.integer "status_cache", default: 0, null: false
-    t.integer "combined_income_value_check"
     t.datetime "discarded_at"
     t.integer "stairowned_value_check"
     t.integer "creation_method", default: 1
@@ -662,8 +663,8 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.string "name"
     t.bigint "organisation_id"
     t.integer "sign_in_count", default: 0, null: false
-    t.datetime "current_sign_in_at", precision: nil
-    t.datetime "last_sign_in_at", precision: nil
+    t.datetime "current_sign_in_at"
+    t.datetime "last_sign_in_at"
     t.string "current_sign_in_ip"
     t.string "last_sign_in_ip"
     t.integer "role"
@@ -671,7 +672,7 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.string "phone"
     t.integer "failed_attempts", default: 0
     t.string "unlock_token"
-    t.datetime "locked_at", precision: nil
+    t.datetime "locked_at"
     t.boolean "is_dpo", default: false
     t.boolean "is_key_contact", default: false
     t.integer "second_factor_attempts_count", default: 0
@@ -679,12 +680,12 @@ ActiveRecord::Schema[7.0].define(version: 2023_07_13_140231) do
     t.string "encrypted_otp_secret_key_iv"
     t.string "encrypted_otp_secret_key_salt"
     t.string "direct_otp"
-    t.datetime "direct_otp_sent_at", precision: nil
+    t.datetime "direct_otp_sent_at"
     t.datetime "totp_timestamp", precision: nil
     t.boolean "active", default: true
     t.string "confirmation_token"
-    t.datetime "confirmed_at", precision: nil
-    t.datetime "confirmation_sent_at", precision: nil
+    t.datetime "confirmed_at"
+    t.datetime "confirmation_sent_at"
     t.string "unconfirmed_email"
     t.boolean "initial_confirmation_sent"
     t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
diff --git a/spec/helpers/organisations_helper_spec.rb b/spec/helpers/organisations_helper_spec.rb
new file mode 100644
index 000000000..f8afb3e04
--- /dev/null
+++ b/spec/helpers/organisations_helper_spec.rb
@@ -0,0 +1,23 @@
+require "rails_helper"
+
+RSpec.describe OrganisationsHelper do
+  include TagHelper
+  describe "display_organisation_attributes" do
+    let(:organisation) { create(:organisation) }
+
+    it "does not include data protection agreement" do
+      expect(display_organisation_attributes(organisation)).to eq(
+        [{ editable: false, name: "Organisation ID", value: "ORG#{organisation.id}" },
+         { editable: true,
+           name: "Address",
+           value: "2 Marsham Street\nLondon\nSW1P 4DF" },
+         { editable: true, name: "Telephone number", value: nil },
+         { editable: false, name: "Type of provider", value: "Local authority" },
+         { editable: false, name: "Registration number", value: "1234" },
+         { editable: false, format: :bullet, name: "Rent periods", value: %w[All] },
+         { editable: false, name: "Owns housing stock", value: "Yes" },
+         { editable: false, name: "Status", value: status_tag(organisation.status) }],
+      )
+    end
+  end
+end
diff --git a/spec/helpers/tag_helper_spec.rb b/spec/helpers/tag_helper_spec.rb
index 3373737de..231323278 100644
--- a/spec/helpers/tag_helper_spec.rb
+++ b/spec/helpers/tag_helper_spec.rb
@@ -20,6 +20,7 @@ RSpec.describe TagHelper do
       expect(status_tag("activating_soon", "app-tag--small")).to eq("<strong class=\"govuk-tag govuk-tag--blue app-tag--small\">Activating soon</strong>")
       expect(status_tag("reactivating_soon", "app-tag--small")).to eq("<strong class=\"govuk-tag govuk-tag--blue app-tag--small\">Reactivating soon</strong>")
       expect(status_tag("deactivated", "app-tag--small")).to eq("<strong class=\"govuk-tag govuk-tag--grey app-tag--small\">Deactivated</strong>")
+      expect(status_tag("merged", "app-tag--small")).to eq("<strong class=\"govuk-tag govuk-tag--orange app-tag--small\">Merged</strong>")
     end
   end
 end
diff --git a/spec/models/organisation_spec.rb b/spec/models/organisation_spec.rb
index c6179b34f..ad9034d35 100644
--- a/spec/models/organisation_spec.rb
+++ b/spec/models/organisation_spec.rb
@@ -230,24 +230,4 @@ RSpec.describe Organisation, type: :model do
       end
     end
   end
-
-  describe "display_organisation_attributes" do
-    let(:organisation) { create(:organisation) }
-
-    it "does not include data protection agreement" do
-      expect(organisation.display_organisation_attributes).to eq(
-        [
-          { editable: false, name: "Organisation ID", value: "ORG#{organisation.id}" },
-          { editable: true,
-            name: "Address",
-            value: "2 Marsham Street\nLondon\nSW1P 4DF" },
-          { editable: true, name: "Telephone number", value: nil },
-          { editable: false, name: "Type of provider", value: "Local authority" },
-          { editable: false, name: "Registration number", value: "1234" },
-          { editable: false, format: :bullet, name: "Rent periods", value: %w[All] },
-          { editable: false, name: "Owns housing stock", value: "Yes" },
-        ],
-      )
-    end
-  end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index d13d648a1..2bd862a90 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -334,6 +334,16 @@ RSpec.describe User, type: :model do
           .to raise_error(ActiveRecord::RecordInvalid, error_message)
       end
     end
+
+    context "when a user is added to a merged organisation" do
+      let(:merged_organisation) { create(:organisation, merge_date: Time.zone.yesterday) }
+      let(:error_message) { "Validation failed: Organisation #{I18n.t('validations.organisation.merged')}" }
+
+      it "validates organisation merge status" do
+        expect { create(:user, organisation: merged_organisation) }
+          .to raise_error(ActiveRecord::RecordInvalid, error_message)
+      end
+    end
   end
 
   describe "delete" do