diff --git a/app/models/validations/sales/sale_information_validations.rb b/app/models/validations/sales/sale_information_validations.rb
index c8a4e46dc..7be2cc957 100644
--- a/app/models/validations/sales/sale_information_validations.rb
+++ b/app/models/validations/sales/sale_information_validations.rb
@@ -100,13 +100,23 @@ module Validations::Sales::SaleInformationValidations
   end
 
   def validate_non_staircasing_mortgage(record)
-    return unless record.mortgage && record.value && record.deposit && record.equity
+    return unless record.value && record.deposit && record.equity
     return unless record.is_not_staircasing?
     return unless record.saledate && record.form.start_year_after_2024?
 
-    if record.mortgage_and_deposit_total != record.expected_shared_ownership_deposit_value
-      %i[mortgage value deposit equity].each do |field|
-        record.errors.add field, I18n.t("validations.sale_information.non_staircasing_mortgage", mortgage_and_deposit_total: record.field_formatted_as_currency("mortgage_and_deposit_total"), expected_shared_ownership_deposit_value: record.field_formatted_as_currency("expected_shared_ownership_deposit_value"))
+    if record.mortgage_used?
+      return unless record.mortgage
+
+      if record.mortgage_and_deposit_total != record.expected_shared_ownership_deposit_value
+        %i[mortgage value deposit equity].each do |field|
+          record.errors.add field, I18n.t("validations.sale_information.non_staircasing_mortgage.mortgage_used", mortgage_and_deposit_total: record.field_formatted_as_currency("mortgage_and_deposit_total"), expected_shared_ownership_deposit_value: record.field_formatted_as_currency("expected_shared_ownership_deposit_value"))
+        end
+      end
+    elsif record.mortgage_not_used?
+      if record.deposit != record.expected_shared_ownership_deposit_value
+        %i[mortgageused value deposit equity].each do |field|
+          record.errors.add field, I18n.t("validations.sale_information.non_staircasing_mortgage.mortgage_not_used", deposit: record.field_formatted_as_currency("deposit"), expected_shared_ownership_deposit_value: record.field_formatted_as_currency("expected_shared_ownership_deposit_value"))
+        end
       end
     end
   end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 37239d234..2589cccdc 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -622,7 +622,9 @@ en:
       value:
         over_discounted_london_max: "The percentage discount multiplied by the purchase price is %{discount_value}. This figure should not be more than £136,400 for properties in London."
         over_discounted_max: "The percentage discount multiplied by the purchase price is %{discount_value}. This figure should not be more than £102,400 for properties outside of London."
-      non_staircasing_mortgage: "The mortgage and deposit added together is %{mortgage_and_deposit_total} and the purchase price times by the equity is %{expected_shared_ownership_deposit_value}. These figures should be the same."
+      non_staircasing_mortgage: 
+        mortgage_used: "The mortgage and deposit added together is %{mortgage_and_deposit_total} and the purchase price times by the equity is %{expected_shared_ownership_deposit_value}. These figures should be the same."
+        mortgage_not_used: "The deposit is %{deposit} and the purchase price times by the equity is %{expected_shared_ownership_deposit_value}. As no mortgage was used, these figures should be the same."
       stairowned:
         mortgageused_dont_know: "The percentage owned has to be 100% if the mortgage used is 'Don’t know'"
     merge_request:
diff --git a/spec/models/validations/sales/sale_information_validations_spec.rb b/spec/models/validations/sales/sale_information_validations_spec.rb
index 3d323112e..a75016352 100644
--- a/spec/models/validations/sales/sale_information_validations_spec.rb
+++ b/spec/models/validations/sales/sale_information_validations_spec.rb
@@ -686,7 +686,7 @@ RSpec.describe Validations::Sales::SaleInformationValidations do
   end
 
   describe "#validate_non_staircasing_mortgage" do
-    let(:record) { FactoryBot.build(:sales_log, mortgage: 10_000, deposit: 5_000, value: 30_000, equity: 28, ownershipsch: 1, type: 30, saledate: now) }
+    let(:record) { FactoryBot.build(:sales_log, mortgageused: 1, mortgage: 10_000, deposit: 5_000, value: 30_000, equity: 28, ownershipsch: 1, type: 30, saledate: now) }
 
     around do |example|
       Timecop.freeze(now) do
@@ -741,6 +741,54 @@ RSpec.describe Validations::Sales::SaleInformationValidations do
           expect(record.errors["equity"]).to be_empty
         end
       end
+
+      context "when mortgage is not used" do
+        before do
+          record.mortgageused = 2
+        end
+
+        context "when DEPOSIT does not equal VALUE * EQUITY/100 " do
+          context "and it is not a staircase transaction" do
+            before do
+              record.staircase = 2
+            end
+
+            it "adds an error" do
+              sale_information_validator.validate_non_staircasing_mortgage(record)
+              expect(record.errors["mortgageused"]).to include("The deposit is £5,000.00 and the purchase price times by the equity is £8,400.00. As no mortgage was used, these figures should be the same.")
+              expect(record.errors["value"]).to include("The deposit is £5,000.00 and the purchase price times by the equity is £8,400.00. As no mortgage was used, these figures should be the same.")
+              expect(record.errors["deposit"]).to include("The deposit is £5,000.00 and the purchase price times by the equity is £8,400.00. As no mortgage was used, these figures should be the same.")
+              expect(record.errors["equity"]).to include("The deposit is £5,000.00 and the purchase price times by the equity is £8,400.00. As no mortgage was used, these figures should be the same.")
+            end
+          end
+
+          context "and it is a staircase transaction" do
+            before do
+              record.staircase = 1
+            end
+
+            it "does not add an error" do
+              sale_information_validator.validate_non_staircasing_mortgage(record)
+              expect(record.errors["mortgageused"]).to be_empty
+              expect(record.errors["value"]).to be_empty
+              expect(record.errors["deposit"]).to be_empty
+              expect(record.errors["equity"]).to be_empty
+            end
+          end
+        end
+
+        context "when DEPOSIT equals VALUE * EQUITY/100" do
+          let(:record) { FactoryBot.build(:sales_log, mortgageused: 2, staircase: 2, deposit: 15_000, value: 30_000, equity: 50, ownershipsch: 1, type: 30, saledate: now) }
+
+          it "does not add an error" do
+            sale_information_validator.validate_non_staircasing_mortgage(record)
+            expect(record.errors["mortgageused"]).to be_empty
+            expect(record.errors["value"]).to be_empty
+            expect(record.errors["deposit"]).to be_empty
+            expect(record.errors["equity"]).to be_empty
+          end
+        end
+      end
     end
 
     context "when it is a 2023 log" do