diff --git a/app/services/merge/merge_organisations_service.rb b/app/services/merge/merge_organisations_service.rb
index 42da7823a..7fee5c45e 100644
--- a/app/services/merge/merge_organisations_service.rb
+++ b/app/services/merge/merge_organisations_service.rb
@@ -1,7 +1,8 @@
 class Merge::MergeOrganisationsService
-  def initialize(absorbing_organisation_id:, merging_organisation_ids:)
+  def initialize(absorbing_organisation_id:, merging_organisation_ids:, merge_date: Time.zone.today)
     @absorbing_organisation = Organisation.find(absorbing_organisation_id)
     @merging_organisations = Organisation.find(merging_organisation_ids)
+    @merge_date = merge_date
   end
 
   def call
@@ -70,12 +71,12 @@ private
         new_scheme.locations << Location.new(location.attributes.except("id", "scheme_id")) unless location.deactivated?
       end
       @merged_schemes[merging_organisation.name] << { name: new_scheme.service_name, code: new_scheme.id }
-      SchemeDeactivationPeriod.create!(scheme:, deactivation_date: Time.zone.now)
+      SchemeDeactivationPeriod.create!(scheme:, deactivation_date: @merge_date)
     end
   end
 
   def merge_lettings_logs(merging_organisation)
-    merging_organisation.owned_lettings_logs.after_date(Time.zone.today).each do |lettings_log|
+    merging_organisation.owned_lettings_logs.after_date(@merge_date.to_time).each do |lettings_log|
       if lettings_log.scheme.present?
         scheme_to_set = @absorbing_organisation.owned_schemes.find_by(service_name: lettings_log.scheme.service_name)
         location_to_set = scheme_to_set.locations.find_by(name: lettings_log.location&.name, postcode: lettings_log.location&.postcode)
@@ -86,20 +87,20 @@ private
       lettings_log.owning_organisation = @absorbing_organisation
       lettings_log.save!
     end
-    merging_organisation.managed_lettings_logs.after_date(Time.zone.today).each do |lettings_log|
+    merging_organisation.managed_lettings_logs.after_date(@merge_date.to_time).each do |lettings_log|
       lettings_log.managing_organisation = @absorbing_organisation
       lettings_log.save!
     end
   end
 
   def merge_sales_logs(merging_organisation)
-    merging_organisation.sales_logs.after_date(Time.zone.today).each do |sales_log|
+    merging_organisation.sales_logs.after_date(@merge_date.to_time).each do |sales_log|
       sales_log.update(owning_organisation: @absorbing_organisation)
     end
   end
 
   def mark_organisation_as_merged(merging_organisation)
-    merging_organisation.update(merge_date: Time.zone.today, absorbing_organisation: @absorbing_organisation)
+    merging_organisation.update(merge_date: @merge_date, absorbing_organisation: @absorbing_organisation)
   end
 
   def log_success_message
diff --git a/spec/services/merge/merge_organisations_service_spec.rb b/spec/services/merge/merge_organisations_service_spec.rb
index 2c2af0f3e..18dff98a9 100644
--- a/spec/services/merge/merge_organisations_service_spec.rb
+++ b/spec/services/merge/merge_organisations_service_spec.rb
@@ -215,6 +215,146 @@ RSpec.describe Merge::MergeOrganisationsService do
           expect(sales_log.owning_organisation).to eq(merging_organisation)
         end
       end
+
+      context "and merge date is provided" do
+        subject(:merge_organisations_service) { described_class.new(absorbing_organisation_id: absorbing_organisation.id, merging_organisation_ids: [merging_organisation_ids], merge_date: Time.zone.yesterday) }
+
+        it "sets merge date on merged organisation" do
+          merge_organisations_service.call
+
+          merging_organisation.reload
+          expect(merging_organisation.merge_date.to_date).to eq(Time.zone.yesterday)
+          expect(merging_organisation.absorbing_organisation_id).to eq(absorbing_organisation.id)
+        end
+
+        context "and merging sales logs" do
+          let!(:sales_log) { create(:sales_log, saledate: Time.zone.yesterday, owning_organisation: merging_organisation) }
+
+          before do
+            create(:sales_log, saledate: Time.zone.today - 2.days, owning_organisation: merging_organisation)
+          end
+
+          it "moves relevant logs" do
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            expect(SalesLog.filter_by_owning_organisation(absorbing_organisation).count).to eq(1)
+            expect(SalesLog.filter_by_owning_organisation(absorbing_organisation).first).to eq(sales_log)
+          end
+
+          it "rolls back if there's an error" do
+            allow(Organisation).to receive(:find).with([merging_organisation_ids]).and_return(Organisation.find(merging_organisation_ids))
+            allow(Organisation).to receive(:find).with(absorbing_organisation.id).and_return(absorbing_organisation)
+            allow(absorbing_organisation).to receive(:save!).and_raise(ActiveRecord::RecordInvalid)
+            expect(Rails.logger).to receive(:error).with("Organisation merge failed with: Record invalid")
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            expect(absorbing_organisation.sales_logs.count).to eq(0)
+            expect(sales_log.owning_organisation).to eq(merging_organisation)
+          end
+        end
+
+        context "and merging lettings logs" do
+          let(:owning_organisation) { create(:organisation, holds_own_stock: true) }
+          let!(:owned_lettings_log) { create(:lettings_log, startdate: Time.zone.yesterday, owning_organisation: merging_organisation, created_by: merging_organisation_user) }
+          let!(:managed_lettings_log) { create(:lettings_log, startdate: Time.zone.yesterday) }
+
+          before do
+            create(:organisation_relationship) { create(:organisation_relationship, parent_organisation: owning_organisation, child_organisation: merging_organisation) }
+            managed_lettings_log.update!(owning_organisation:, managing_organisation: merging_organisation, created_by: merging_organisation_user)
+            create(:lettings_log, startdate: Time.zone.today - 2.days, owning_organisation: merging_organisation, created_by: merging_organisation_user)
+            create(:lettings_log, startdate: Time.zone.today - 2.days, owning_organisation:, managing_organisation: merging_organisation, created_by: merging_organisation_user)
+          end
+
+          it "moves relevant logs" do
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            expect(LettingsLog.filter_by_owning_organisation(absorbing_organisation).count).to eq(1)
+            expect(LettingsLog.filter_by_owning_organisation(absorbing_organisation).first).to eq(owned_lettings_log)
+            expect(LettingsLog.filter_by_managing_organisation(absorbing_organisation).count).to eq(2)
+            expect(LettingsLog.filter_by_managing_organisation(absorbing_organisation)).to include(managed_lettings_log)
+            expect(LettingsLog.filter_by_managing_organisation(absorbing_organisation)).to include(owned_lettings_log)
+          end
+
+          it "rolls back if there's an error" do
+            allow(Organisation).to receive(:find).with([merging_organisation_ids]).and_return(Organisation.find(merging_organisation_ids))
+            allow(Organisation).to receive(:find).with(absorbing_organisation.id).and_return(absorbing_organisation)
+            allow(absorbing_organisation).to receive(:save!).and_raise(ActiveRecord::RecordInvalid)
+            expect(Rails.logger).to receive(:error).with("Organisation merge failed with: Record invalid")
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            expect(absorbing_organisation.lettings_logs.count).to eq(0)
+            expect(owned_lettings_log.owning_organisation).to eq(merging_organisation)
+            expect(managed_lettings_log.managing_organisation).to eq(merging_organisation)
+          end
+        end
+
+        context "and merging organisation schemes and locations" do
+          let!(:scheme) { create(:scheme, owning_organisation: merging_organisation) }
+          let!(:location) { create(:location, scheme:) }
+          let!(:deactivated_location) { create(:location, scheme:) }
+          let!(:deactivated_scheme) { create(:scheme, owning_organisation: merging_organisation) }
+          let!(:owned_lettings_log) { create(:lettings_log, :sh, scheme:, location:, startdate: Time.zone.tomorrow, owning_organisation: merging_organisation) }
+          let!(:owned_lettings_log_no_location) { create(:lettings_log, :sh, scheme:, startdate: Time.zone.tomorrow, owning_organisation: merging_organisation) }
+
+          before do
+            create(:location, scheme:, name: "fake location", postcode: "A1 1AA")
+            create(:location, scheme: deactivated_scheme)
+            create(:scheme_deactivation_period, scheme: deactivated_scheme, deactivation_date: Time.zone.today - 1.month)
+            create(:location_deactivation_period, location: deactivated_location, deactivation_date: Time.zone.today - 1.month)
+            create(:lettings_log, scheme:, location:, startdate: Time.zone.yesterday)
+            create(:lettings_log, startdate: Time.zone.tomorrow, managing_organisation: merging_organisation)
+          end
+
+          it "combines organisation schemes and locations" do
+            expect(Rails.logger).to receive(:info).with("Merged users from fake org:")
+            expect(Rails.logger).to receive(:info).with("\tDanny Rojas (#{merging_organisation.data_protection_officers.first.email})")
+            expect(Rails.logger).to receive(:info).with("\tfake name (fake@email.com)")
+            expect(Rails.logger).to receive(:info).with("New schemes from fake org:")
+            expect(Rails.logger).to receive(:info).with(/\t#{scheme.service_name} \(S/)
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            expect(absorbing_organisation.owned_schemes.count).to eq(1)
+            expect(absorbing_organisation.owned_schemes.first.service_name).to eq(scheme.service_name)
+            expect(absorbing_organisation.owned_schemes.first.locations.count).to eq(2)
+            expect(absorbing_organisation.owned_schemes.first.locations.first.postcode).to eq(location.postcode)
+            expect(scheme.scheme_deactivation_periods.count).to eq(1)
+            expect(scheme.scheme_deactivation_periods.first.deactivation_date.to_date).to eq(Time.zone.yesterday)
+          end
+
+          it "moves relevant logs and assigns the new scheme" do
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            merging_organisation.reload
+            expect(absorbing_organisation.owned_lettings_logs.count).to eq(2)
+            expect(absorbing_organisation.managed_lettings_logs.count).to eq(1)
+            expect(absorbing_organisation.owned_lettings_logs.find(owned_lettings_log.id).scheme).to eq(absorbing_organisation.owned_schemes.first)
+            expect(absorbing_organisation.owned_lettings_logs.find(owned_lettings_log.id).location).to eq(absorbing_organisation.owned_schemes.first.locations.first)
+            expect(absorbing_organisation.owned_lettings_logs.find(owned_lettings_log_no_location.id).scheme).to eq(absorbing_organisation.owned_schemes.first)
+            expect(absorbing_organisation.owned_lettings_logs.find(owned_lettings_log_no_location.id).location).to eq(nil)
+          end
+
+          it "rolls back if there's an error" do
+            allow(Organisation).to receive(:find).with([merging_organisation_ids]).and_return(Organisation.find(merging_organisation_ids))
+            allow(Organisation).to receive(:find).with(absorbing_organisation.id).and_return(absorbing_organisation)
+            allow(absorbing_organisation).to receive(:save!).and_raise(ActiveRecord::RecordInvalid)
+            expect(Rails.logger).to receive(:error).with("Organisation merge failed with: Record invalid")
+            merge_organisations_service.call
+
+            absorbing_organisation.reload
+            merging_organisation.reload
+            expect(absorbing_organisation.owned_schemes.count).to eq(0)
+            expect(scheme.scheme_deactivation_periods.count).to eq(0)
+            expect(owned_lettings_log.owning_organisation).to eq(merging_organisation)
+            expect(owned_lettings_log_no_location.owning_organisation).to eq(merging_organisation)
+          end
+        end
+      end
     end
 
     context "when merging a multiple organisations into an existing organisation" do
@@ -318,6 +458,21 @@ RSpec.describe Merge::MergeOrganisationsService do
           expect(absorbing_organisation.child_organisations).to include(absorbing_organisation_relationship.child_organisation)
         end
       end
+
+      context "and merge date is provided" do
+        subject(:merge_organisations_service) { described_class.new(absorbing_organisation_id: absorbing_organisation.id, merging_organisation_ids: [merging_organisation_ids], merge_date: Time.zone.yesterday) }
+
+        it "sets merge date and absorbing organisation on merged organisations" do
+          merge_organisations_service.call
+
+          merging_organisation.reload
+          merging_organisation_too.reload
+          expect(merging_organisation.merge_date.to_date).to eq(Time.zone.yesterday)
+          expect(merging_organisation.absorbing_organisation_id).to eq(absorbing_organisation.id)
+          expect(merging_organisation_too.merge_date.to_date).to eq(Time.zone.yesterday)
+          expect(merging_organisation_too.absorbing_organisation_id).to eq(absorbing_organisation.id)
+        end
+      end
     end
   end
 end