diff --git a/app/models/lettings_log.rb b/app/models/lettings_log.rb
index 5bd06c972..a38f1eba1 100644
--- a/app/models/lettings_log.rb
+++ b/app/models/lettings_log.rb
@@ -559,6 +559,7 @@ class LettingsLog < Log
     return unless updated_by&.support?
     return if owning_organisation.blank? || managing_organisation.blank? || created_by.blank?
     return if created_by&.organisation == managing_organisation || created_by&.organisation == owning_organisation
+    return if created_by&.organisation == owning_organisation.absorbing_organisation || created_by&.organisation == managing_organisation.absorbing_organisation
 
     update!(created_by: nil)
   end
diff --git a/app/models/sales_log.rb b/app/models/sales_log.rb
index bf059cc88..4345b9694 100644
--- a/app/models/sales_log.rb
+++ b/app/models/sales_log.rb
@@ -318,6 +318,7 @@ class SalesLog < Log
     return unless updated_by&.support?
     return if owning_organisation.blank? || created_by.blank?
     return if created_by&.organisation == owning_organisation
+    return if created_by&.organisation == owning_organisation.absorbing_organisation
 
     update!(created_by: nil)
   end
diff --git a/spec/requests/form_controller_spec.rb b/spec/requests/form_controller_spec.rb
index fbe3dbb1d..94e8aeb30 100644
--- a/spec/requests/form_controller_spec.rb
+++ b/spec/requests/form_controller_spec.rb
@@ -189,6 +189,62 @@ RSpec.describe FormController, type: :request do
       end
     end
 
+    context "when submitting a sales log with valid owning organisation" do
+      let(:sales_log) { create(:sales_log) }
+      let(:created_by) { managing_organisation.users.first }
+      let(:params) do
+        {
+          id: sales_log.id,
+          sales_log: {
+            page: "organisation",
+            owning_organisation_id: managing_organisation.id,
+          },
+        }
+      end
+
+      before do
+        sales_log.update!(owning_organisation: managing_organisation, created_by:)
+        sales_log.reload
+      end
+
+      it "does not reset created by" do
+        post "/sales-logs/#{sales_log.id}/organisation", params: params
+        expect(response).to redirect_to("/sales-logs/#{sales_log.id}/created-by")
+        follow_redirect!
+        sales_log.reload
+        expect(sales_log.created_by).to eq(created_by)
+      end
+    end
+
+    context "when submitting a sales log with valid merged owning organisation" do
+      let(:sales_log) { create(:sales_log) }
+      let(:created_by) { managing_organisation.users.first }
+      let(:merged_organisation) { create(:organisation) }
+      let(:params) do
+        {
+          id: sales_log.id,
+          sales_log: {
+            page: "organisation",
+            owning_organisation_id: merged_organisation.id,
+          },
+        }
+      end
+
+      before do
+        merged_organisation.update!(merge_date: Time.zone.today, absorbing_organisation: managing_organisation)
+        sales_log.update!(owning_organisation: managing_organisation, created_by:)
+        sales_log.reload
+      end
+
+      it "does not reset created by" do
+        post "/sales-logs/#{sales_log.id}/organisation", params: params
+        expect(response).to redirect_to("/sales-logs/#{sales_log.id}/created-by")
+        follow_redirect!
+        sales_log.reload
+        expect(sales_log.created_by).to eq(created_by)
+      end
+    end
+
     context "with valid managing organisation" do
       let(:params) do
         {
@@ -214,6 +270,33 @@ RSpec.describe FormController, type: :request do
       end
     end
 
+    context "with valid absorbed managing organisation" do
+      let(:params) do
+        {
+          id: lettings_log.id,
+          lettings_log: {
+            page: "stock_owner",
+            owning_organisation_id: stock_owner.id,
+          },
+        }
+      end
+      let(:merged_org) { create(:organisation) }
+
+      before do
+        merged_org.update!(merge_date: Time.zone.today, absorbing_organisation: organisation)
+        lettings_log.update!(owning_organisation: merged_org, created_by: user, managing_organisation: merged_org)
+        lettings_log.reload
+      end
+
+      it "does not reset created by" do
+        post "/lettings-logs/#{lettings_log.id}/stock-owner", params: params
+        expect(response).to redirect_to("/lettings-logs/#{lettings_log.id}/managing-organisation")
+        follow_redirect!
+        lettings_log.reload
+        expect(lettings_log.created_by).to eq(user)
+      end
+    end
+
     context "with only adding the stock owner" do
       let(:params) do
         {