diff --git a/app/services/merge/merge_organisations_service.rb b/app/services/merge/merge_organisations_service.rb
index 7fee5c45e..30e3b0995 100644
--- a/app/services/merge/merge_organisations_service.rb
+++ b/app/services/merge/merge_organisations_service.rb
@@ -2,7 +2,7 @@ class Merge::MergeOrganisationsService
   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
+    @merge_date = merge_date || Time.zone.today
   end
 
   def call
diff --git a/lib/tasks/merge_organisations.rake b/lib/tasks/merge_organisations.rake
index 820343883..17dfe1c4f 100644
--- a/lib/tasks/merge_organisations.rake
+++ b/lib/tasks/merge_organisations.rake
@@ -1,12 +1,19 @@
 namespace :merge do
   desc "Merge organisations into one"
-  task :merge_organisations, %i[absorbing_organisation_id merging_organisation_ids] => :environment do |_task, args|
+  task :merge_organisations, %i[absorbing_organisation_id merging_organisation_ids merge_date] => :environment do |_task, args|
     absorbing_organisation_id = args[:absorbing_organisation_id]
     merging_organisation_ids = args[:merging_organisation_ids]&.split(" ")&.map(&:to_i)
+    begin
+      merge_date = args[:merge_date].present? ? Date.parse(args[:merge_date]) : nil
+    rescue StandardError
+      raise "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]. Merge date must be in format YYYY-MM-DD"
+    end
 
-    raise "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids]" if merging_organisation_ids.blank? || absorbing_organisation_id.blank?
+    if merging_organisation_ids.blank? || absorbing_organisation_id.blank?
+      raise "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]"
+    end
 
-    service = Merge::MergeOrganisationsService.new(absorbing_organisation_id:, merging_organisation_ids:)
+    service = Merge::MergeOrganisationsService.new(absorbing_organisation_id:, merging_organisation_ids:, merge_date:)
     service.call
   end
 end
diff --git a/spec/lib/tasks/merge_organisations_spec.rb b/spec/lib/tasks/merge_organisations_spec.rb
index 4155a4389..20be80de4 100644
--- a/spec/lib/tasks/merge_organisations_spec.rb
+++ b/spec/lib/tasks/merge_organisations_spec.rb
@@ -20,22 +20,32 @@ RSpec.describe "emails" do
 
     context "when the rake task is run" do
       it "raises an error when no parameters are given" do
-        expect { task.invoke(nil) }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids]")
+        expect { task.invoke(nil) }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]")
       end
 
       it "raises an error when only absorbing organisation is given" do
-        expect { task.invoke(1, nil) }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids]")
+        expect { task.invoke(1, nil) }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]")
       end
 
       it "raises an error when only merging organisations are given" do
-        expect { task.invoke(nil, "1 2") }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids]")
+        expect { task.invoke(nil, "1 2") }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]")
       end
 
-      it "raises runs the service with correct organisation IDs" do
-        expect(Merge::MergeOrganisationsService).to receive(:new).with(absorbing_organisation_id: 1, merging_organisation_ids: [2, 3]).once
+      it "raises an error when the merge date given is not valid" do
+        expect { task.invoke("3", "1 2", "invalid_date") }.to raise_error(RuntimeError, "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids, merge_date]. Merge date must be in format YYYY-MM-DD")
+      end
+
+      it "runs the service with correct organisation IDs" do
+        expect(Merge::MergeOrganisationsService).to receive(:new).with(absorbing_organisation_id: 1, merging_organisation_ids: [2, 3], merge_date: nil).once
         expect(merge_organisations_service).to receive(:call).once
         task.invoke(1, "2 3")
       end
+
+      it "runs the service with correct date when date is given" do
+        expect(Merge::MergeOrganisationsService).to receive(:new).with(absorbing_organisation_id: 1, merging_organisation_ids: [2, 3], merge_date: Time.zone.local(2021, 1, 13)).once
+        expect(merge_organisations_service).to receive(:call).once
+        task.invoke(1, "2 3", "2021-01-13")
+      end
     end
   end
 end
diff --git a/spec/services/merge/merge_organisations_service_spec.rb b/spec/services/merge/merge_organisations_service_spec.rb
index 18dff98a9..071812dd1 100644
--- a/spec/services/merge/merge_organisations_service_spec.rb
+++ b/spec/services/merge/merge_organisations_service_spec.rb
@@ -1,7 +1,7 @@
 require "rails_helper"
 
 RSpec.describe Merge::MergeOrganisationsService do
-  subject(:merge_organisations_service) { described_class.new(absorbing_organisation_id: absorbing_organisation.id, merging_organisation_ids: [merging_organisation_ids]) }
+  subject(:merge_organisations_service) { described_class.new(absorbing_organisation_id: absorbing_organisation.id, merging_organisation_ids: [merging_organisation_ids], merge_date: nil) }
 
   let(:absorbing_organisation) {    create(:organisation, holds_own_stock: false) }
   let(:absorbing_organisation_user) { create(:user, organisation: absorbing_organisation) }