diff --git a/lib/tasks/merge_organisations.rake b/lib/tasks/merge_organisations.rake
index 0df38a2ac..820343883 100644
--- a/lib/tasks/merge_organisations.rake
+++ b/lib/tasks/merge_organisations.rake
@@ -2,7 +2,7 @@ namespace :merge do
   desc "Merge organisations into one"
   task :merge_organisations, %i[absorbing_organisation_id merging_organisation_ids] => :environment do |_task, args|
     absorbing_organisation_id = args[:absorbing_organisation_id]
-    merging_organisation_ids = args[:merging_organisation_ids]&.split(",")&.map(&:to_i)
+    merging_organisation_ids = args[:merging_organisation_ids]&.split(" ")&.map(&:to_i)
 
     raise "Usage: rake merge:merge_organisations[absorbing_organisation_id, merging_organisation_ids]" if merging_organisation_ids.blank? || absorbing_organisation_id.blank?
 
diff --git a/spec/lib/tasks/merge_organisations_spec.rb b/spec/lib/tasks/merge_organisations_spec.rb
index efb3fe99d..4155a4389 100644
--- a/spec/lib/tasks/merge_organisations_spec.rb
+++ b/spec/lib/tasks/merge_organisations_spec.rb
@@ -28,13 +28,13 @@ RSpec.describe "emails" do
       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]")
       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
         expect(merge_organisations_service).to receive(:call).once
-        task.invoke(1, "2,3")
+        task.invoke(1, "2 3")
       end
     end
   end
diff --git a/spec/services/merge/merge_organisations_service_spec.rb b/spec/services/merge/merge_organisations_service_spec.rb
index 9ec6144b7..10cff2aa9 100644
--- a/spec/services/merge/merge_organisations_service_spec.rb
+++ b/spec/services/merge/merge_organisations_service_spec.rb
@@ -45,7 +45,7 @@ RSpec.describe Merge::MergeOrganisationsService do
 
         absorbing_organisation.reload
         expect(absorbing_organisation.holds_own_stock).to eq(false)
-        # expect(merging_organisation.merge_date).to eq(nil)
+        expect(merging_organisation.merge_date).to eq(nil)
         expect(merging_organisation_user.organisation).to eq(merging_organisation)
       end
 
@@ -205,5 +205,55 @@ RSpec.describe Merge::MergeOrganisationsService do
         end
       end
     end
+
+    context "when merging a multiple organisations into an existing organisation" do
+      let(:merging_organisation) { create(:organisation, holds_own_stock: true, name: "fake org") }
+      let(:merging_organisation_too) { create(:organisation, holds_own_stock: true, name: "second org") }
+
+      let(:merging_organisation_ids) { [merging_organisation.id, merging_organisation_too.id] }
+      let!(:merging_organisation_user) { create(:user, organisation: merging_organisation, name: "fake name", email: "fake@email.com") }
+
+      before do
+        create_list(:user, 5, organisation: merging_organisation_too)
+      end
+
+      it "moves the users from merging organisations to absorbing organisation" do
+        expect(Rails.logger).to receive(:info).with(/Merged users from second org:/)
+        expect(Rails.logger).to receive(:info).with("New schemes from fake org:\nNew schemes from second org:\n")
+        merge_organisations_service.call
+
+        merging_organisation_user.reload
+        expect(merging_organisation_user.organisation).to eq(absorbing_organisation)
+      end
+
+      it "sets merge date 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.today)
+        expect(merging_organisation_too.merge_date.to_date).to eq(Time.zone.today)
+      end
+
+      it "combines organisation data" do
+        merge_organisations_service.call
+
+        absorbing_organisation.reload
+        expect(absorbing_organisation.holds_own_stock).to eq(true)
+      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.holds_own_stock).to eq(false)
+        expect(merging_organisation.merge_date).to eq(nil)
+        expect(merging_organisation_user.organisation).to eq(merging_organisation)
+      end
+    end
   end
 end