diff --git a/app/models/derived_variables/lettings_log_variables.rb b/app/models/derived_variables/lettings_log_variables.rb
index 7d1274540..b2adf9fa1 100644
--- a/app/models/derived_variables/lettings_log_variables.rb
+++ b/app/models/derived_variables/lettings_log_variables.rb
@@ -95,6 +95,8 @@ module DerivedVariables::LettingsLogVariables
 
     set_housingneeds_fields if housingneeds?
 
+    self.uprn_known = 0 if address_answered_without_uprn?
+
     if uprn_known&.zero?
       self.uprn = nil
     end
@@ -310,6 +312,10 @@ private
     self.county = nil
   end
 
+  def address_answered_without_uprn?
+    [address_line1, town_or_city].all?(&:present?) && uprn.nil? && form.start_date.year >= 2023
+  end
+
   def get_lar
     return 1 if rent_type == 2
     return 2 if rent_type == 1
diff --git a/app/models/derived_variables/sales_log_variables.rb b/app/models/derived_variables/sales_log_variables.rb
index 308a62bb8..6532b228f 100644
--- a/app/models/derived_variables/sales_log_variables.rb
+++ b/app/models/derived_variables/sales_log_variables.rb
@@ -24,6 +24,8 @@ module DerivedVariables::SalesLogVariables
     self.hhmemb = number_of_household_members
     self.hhtype = household_type
 
+    self.uprn_known = 0 if address_answered_without_uprn?
+
     if uprn_known&.zero?
       self.uprn = nil
     end
@@ -148,4 +150,8 @@ private
   def only_one_elder?
     total_elder == 1 && total_adult.zero? && totchild.zero?
   end
+
+  def address_answered_without_uprn?
+    [address_line1, town_or_city].all?(&:present?) && uprn.nil? && form.start_date.year >= 2023
+  end
 end
diff --git a/spec/models/form/lettings/questions/uprn_spec.rb b/spec/models/form/lettings/questions/uprn_spec.rb
index b11ddc7d9..98599b99f 100644
--- a/spec/models/form/lettings/questions/uprn_spec.rb
+++ b/spec/models/form/lettings/questions/uprn_spec.rb
@@ -62,11 +62,13 @@ RSpec.describe Form::Lettings::Questions::Uprn, type: :model do
           postcode_full: "AA1 1AA",
           la: "E09000003",
           uprn_known:,
+          uprn:,
         )
       end
 
       context "when uprn known nil" do
         let(:uprn_known) { nil }
+        let(:uprn) { nil }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to be_nil
@@ -75,6 +77,7 @@ RSpec.describe Form::Lettings::Questions::Uprn, type: :model do
 
       context "when uprn known" do
         let(:uprn_known) { 1 }
+        let(:uprn) { 123_456_789 }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to eq(
@@ -85,6 +88,7 @@ RSpec.describe Form::Lettings::Questions::Uprn, type: :model do
 
       context "when uprn not known" do
         let(:uprn_known) { 0 }
+        let(:uprn) { nil }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to be_nil
diff --git a/spec/models/form/sales/questions/uprn_spec.rb b/spec/models/form/sales/questions/uprn_spec.rb
index 3d9a22a14..e1a1491ad 100644
--- a/spec/models/form/sales/questions/uprn_spec.rb
+++ b/spec/models/form/sales/questions/uprn_spec.rb
@@ -56,18 +56,19 @@ RSpec.describe Form::Sales::Questions::Uprn, type: :model do
       let(:log) do
         create(
           :sales_log,
-          :completed,
           address_line1: "1, Test Street",
           town_or_city: "Test Town",
           county: "Test County",
           postcode_full: "AA1 1AA",
           la: "E09000003",
           uprn_known:,
+          uprn:,
         )
       end
 
       context "when uprn known nil" do
         let(:uprn_known) { nil }
+        let(:uprn) { nil }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to be_nil
@@ -76,6 +77,7 @@ RSpec.describe Form::Sales::Questions::Uprn, type: :model do
 
       context "when uprn known" do
         let(:uprn_known) { 1 }
+        let(:uprn) { 123_456_789 }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to eq(
@@ -86,6 +88,7 @@ RSpec.describe Form::Sales::Questions::Uprn, type: :model do
 
       context "when uprn not known" do
         let(:uprn_known) { 0 }
+        let(:uprn) { nil }
 
         it "returns formatted value" do
           expect(question.get_extra_check_answer_value(log)).to be_nil