diff --git a/app/models/validations/property_validations.rb b/app/models/validations/property_validations.rb
index 107460dec..26b569f85 100644
--- a/app/models/validations/property_validations.rb
+++ b/app/models/validations/property_validations.rb
@@ -27,6 +27,10 @@ module Validations::PropertyValidations
     if record.la.present? && !LONDON_BOROUGHS.include?(record.la) && (record.rent_type == "London Affordable rent" || record.rent_type == "London living rent")
       record.errors.add :la, I18n.t("validations.property.la.london_rent")
     end
+
+    if record.la_known == "Yes" && record.la.blank?
+      record.errors.add :la, I18n.t("validations.property.la.la_known")
+    end
   end
 
   FIRST_LET_VACANCY_REASONS = ["First let of new-build property",
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 9a5b8fad9..71bebaf85 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -55,6 +55,7 @@ en:
         relet_number: "Property number of times relet must be between 0 and 20"
       la:
         london_rent: "Local authority has to be in London"
+        la_known: "Enter a local authority"
       rsnvac:
         first_let_not_social: "Reason for vacancy cannot be first let if unit has been previously let as social housing"
         first_let_social: "Reason for vacancy must be first let if unit has been previously let as social housing"
diff --git a/spec/models/validations/property_validations_spec.rb b/spec/models/validations/property_validations_spec.rb
index fb11039c9..bbf650059 100644
--- a/spec/models/validations/property_validations_spec.rb
+++ b/spec/models/validations/property_validations_spec.rb
@@ -157,6 +157,15 @@ RSpec.describe Validations::PropertyValidations do
         expect(record.errors["la"]).to be_empty
       end
     end
+
+    context "when previous la is known" do
+      it "la has to be provided" do
+        record.la_known = "Yes"
+        property_validator.validate_la(record)
+        expect(record.errors["la"])
+          .to include(match I18n.t("validations.property.la.la_known"))
+      end
+    end
   end
 
   describe "#validate_unitletas" do