diff --git a/app/models/form/sales/pages/mortgage_amount.rb b/app/models/form/sales/pages/mortgage_amount.rb
index 793570b46..73e306c2a 100644
--- a/app/models/form/sales/pages/mortgage_amount.rb
+++ b/app/models/form/sales/pages/mortgage_amount.rb
@@ -3,9 +3,7 @@ class Form::Sales::Pages::MortgageAmount < ::Form::Page
     super(id, hsh, subsection)
     @ownershipsch = ownershipsch
     @header = "Mortgage Amount"
-    @depends_on = [{
-      "mortgageused" => 1,
-    }]
+    @depends_on = [{ "mortgage_used?" => true }]
   end
 
   def questions
diff --git a/app/models/form/sales/questions/mortgage_amount.rb b/app/models/form/sales/questions/mortgage_amount.rb
index 12959709a..9b199b2aa 100644
--- a/app/models/form/sales/questions/mortgage_amount.rb
+++ b/app/models/form/sales/questions/mortgage_amount.rb
@@ -5,7 +5,7 @@ class Form::Sales::Questions::MortgageAmount < ::Form::Question
     @check_answer_label = "Mortgage amount"
     @header = "What is the mortgage amount?"
     @type = "numeric"
-    @min = 0
+    @min = 1
     @width = 5
     @prefix = "£"
     @hint_text = "Enter the amount of mortgage agreed with the mortgage lender. Exclude any deposits or cash payments. Numeric in pounds. Rounded to the nearest pound."
diff --git a/app/models/sales_log.rb b/app/models/sales_log.rb
index ba2ea4fa8..2a6e1a6d3 100644
--- a/app/models/sales_log.rb
+++ b/app/models/sales_log.rb
@@ -243,6 +243,10 @@ class SalesLog < Log
     ownershipsch == 2
   end
 
+  def mortgage_used?
+    mortgageused == 1
+  end
+
   def mortgage_not_used?
     mortgageused == 2
   end
diff --git a/app/models/validations/sales/financial_validations.rb b/app/models/validations/sales/financial_validations.rb
index faf436afa..61772be93 100644
--- a/app/models/validations/sales/financial_validations.rb
+++ b/app/models/validations/sales/financial_validations.rb
@@ -36,6 +36,10 @@ module Validations::Sales::FinancialValidations
     end
   end
 
+  def validate_mortgage(record)
+    record.errors.add :mortgage, I18n.t("validations.financial.mortgage") if record.mortgage_used? && record.mortgage&.zero?
+  end
+
   def validate_cash_discount(record)
     return unless record.cashdis
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 36d8b93f8..56caa6a59 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -316,6 +316,7 @@ en:
       equity:
         under_min: "The minimum initial equity stake for this type of shared ownership sale is %{min_equity}%"
         over_max: "The maximum initial equity stake is %{max_equity}%"
+      mortgage: "Mortgage value cannot be £0 if a mortgage was used for the purchase of this property"
 
     household:
       reasonpref:
diff --git a/spec/models/form/sales/pages/mortgage_amount_spec.rb b/spec/models/form/sales/pages/mortgage_amount_spec.rb
index 551788fbb..c6f6f924e 100644
--- a/spec/models/form/sales/pages/mortgage_amount_spec.rb
+++ b/spec/models/form/sales/pages/mortgage_amount_spec.rb
@@ -28,8 +28,6 @@ RSpec.describe Form::Sales::Pages::MortgageAmount, type: :model do
   end
 
   it "has correct depends_on" do
-    expect(page.depends_on).to eq([{
-      "mortgageused" => 1,
-    }])
+    expect(page.depends_on).to eq([{ "mortgage_used?" => true }])
   end
 end
diff --git a/spec/models/form/sales/questions/mortgage_amount_spec.rb b/spec/models/form/sales/questions/mortgage_amount_spec.rb
index 328406ecd..758101867 100644
--- a/spec/models/form/sales/questions/mortgage_amount_spec.rb
+++ b/spec/models/form/sales/questions/mortgage_amount_spec.rb
@@ -8,7 +8,7 @@ RSpec.describe Form::Sales::Questions::MortgageAmount, type: :model do
   let(:page) { instance_double(Form::Page) }
 
   it "has correct page" do
-    expect(question.page).to eq(page)
+    expect(question.page).to be(page)
   end
 
   it "has the correct id" do
@@ -36,7 +36,7 @@ RSpec.describe Form::Sales::Questions::MortgageAmount, type: :model do
   end
 
   it "has correct width" do
-    expect(question.width).to eq(5)
+    expect(question.width).to be(5)
   end
 
   it "has correct prefix" do
@@ -44,6 +44,6 @@ RSpec.describe Form::Sales::Questions::MortgageAmount, type: :model do
   end
 
   it "has correct min" do
-    expect(question.min).to eq(0)
+    expect(question.min).to be(1)
   end
 end
diff --git a/spec/models/validations/sales/financial_validations_spec.rb b/spec/models/validations/sales/financial_validations_spec.rb
index b60ef5e6a..e1eb81dea 100644
--- a/spec/models/validations/sales/financial_validations_spec.rb
+++ b/spec/models/validations/sales/financial_validations_spec.rb
@@ -113,6 +113,24 @@ RSpec.describe Validations::Sales::FinancialValidations do
     end
   end
 
+  describe "#validate_mortgage" do
+    let(:record) { FactoryBot.create(:sales_log) }
+
+    it "adds an error is the mortgage is zero" do
+      record.mortgageused = 1
+      record.mortgage = 0
+      financial_validator.validate_mortgage(record)
+      expect(record.errors[:mortgage]).to include I18n.t("validations.financial.mortgage")
+    end
+
+    it "does not add an error is the mortgage is positive" do
+      record.mortgageused = 1
+      record.mortgage = 234
+      financial_validator.validate_mortgage(record)
+      expect(record.errors).to be_empty
+    end
+  end
+
   describe "#validate_cash_discount" do
     let(:record) { FactoryBot.create(:sales_log) }