diff --git a/app/models/validations/sales/financial_validations.rb b/app/models/validations/sales/financial_validations.rb
index 21f3743ca..255f12bf2 100644
--- a/app/models/validations/sales/financial_validations.rb
+++ b/app/models/validations/sales/financial_validations.rb
@@ -52,6 +52,21 @@ module Validations::Sales::FinancialValidations
     end
   end
 
+  def validate_percentage_bought_at_least_threshold(record)
+    return unless record.stairbought && record.type
+
+    threshold = if [2, 16, 18, 24].include? record.type
+                  10
+                else
+                  1
+                end
+
+    if threshold && record.stairbought < threshold
+      record.errors.add :stairbought, I18n.t("validations.financial.staircasing.percentage_bought_must_be_at_least_threshold", threshold:)
+      record.errors.add :type, I18n.t("validations.setup.type.percentage_bought_must_be_at_least_threshold", threshold:)
+    end
+  end
+
   def validate_child_income(record)
     return unless record.income2 && record.ecstat2
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index d21bb5b5c..e17c0ab9b 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -159,6 +159,8 @@ en:
           Enter a date within the %{current_start_year_short}/%{current_end_year_short} financial year, which is between %{current_start_year_long} and %{current_end_year_long}
         previous_and_current_financial_year:
           "Enter a date within the %{previous_start_year_short}/%{previous_end_year_short} or %{previous_end_year_short}/%{current_end_year_short} financial years, which is between %{previous_start_year_long} and %{current_end_year_long}"
+      type:
+        percentage_bought_must_be_at_least_threshold: "The minimum increase in equity while staircasing is %{threshold}% for this shared ownership type"
 
       startdate:
         later_than_14_days_after: "The tenancy start date must not be later than 14 days from today’s date"
@@ -302,6 +304,7 @@ en:
       staircasing:
         percentage_bought_must_be_greater_than_percentage_owned: "Total percentage buyer now owns must be more than percentage bought in this transaction"
         older_person_percentage_owned_maximum_75: "Percentage cannot be above 75% under Older Person's Shared Ownership"
+        percentage_bought_must_be_at_least_threshold: "The minimum increase in equity while staircasing is %{threshold}%"
 
     household:
       reasonpref:
diff --git a/spec/models/validations/sales/financial_validations_spec.rb b/spec/models/validations/sales/financial_validations_spec.rb
index fae0e4536..d9406aec9 100644
--- a/spec/models/validations/sales/financial_validations_spec.rb
+++ b/spec/models/validations/sales/financial_validations_spec.rb
@@ -160,6 +160,48 @@ RSpec.describe Validations::Sales::FinancialValidations do
     end
   end
 
+  describe "#validate_percentage_bought_at_least_threshold" do
+    let(:record) { FactoryBot.create(:sales_log) }
+
+    it "adds an error to stairbought and type if the percentage bought is less than the threshold (which is 1% by default, but higher for some shared ownership types)" do
+      record.stairbought = 9
+      [2, 16, 18, 24].each do |type|
+        record.type = type
+        financial_validator.validate_percentage_bought_at_least_threshold(record)
+        expect(record.errors["stairbought"]).to eq(["The minimum increase in equity while staircasing is 10%"])
+        expect(record.errors["type"]).to eq(["The minimum increase in equity while staircasing is 10% for this shared ownership type"])
+        record.errors.clear
+      end
+
+      record.stairbought = 0
+      [28, 30, 31, 32].each do |type|
+        record.type = type
+        financial_validator.validate_percentage_bought_at_least_threshold(record)
+        expect(record.errors["stairbought"]).to eq(["The minimum increase in equity while staircasing is 1%"])
+        expect(record.errors["type"]).to eq(["The minimum increase in equity while staircasing is 1% for this shared ownership type"])
+        record.errors.clear
+      end
+    end
+
+    it "doesn't add an error to stairbought and type if the percentage bought is less than the threshold (which is 1% by default, but higher for some shared ownership types)" do
+      record.stairbought = 10
+      [2, 16, 18, 24].each do |type|
+        record.type = type
+        financial_validator.validate_percentage_bought_at_least_threshold(record)
+        expect(record.errors).to be_empty
+        record.errors.clear
+      end
+
+      record.stairbought = 1
+      [28, 30, 31, 32].each do |type|
+        record.type = type
+        financial_validator.validate_percentage_bought_at_least_threshold(record)
+        expect(record.errors).to be_empty
+        record.errors.clear
+      end
+    end
+  end
+
   describe "#validate_percentage_owned_not_too_much_if_older_person" do
     let(:record) { FactoryBot.create(:sales_log) }