diff --git a/app/models/derived_variables/lettings_log_variables.rb b/app/models/derived_variables/lettings_log_variables.rb
index 56b47e9ad..1de14c866 100644
--- a/app/models/derived_variables/lettings_log_variables.rb
+++ b/app/models/derived_variables/lettings_log_variables.rb
@@ -113,9 +113,17 @@ module DerivedVariables::LettingsLogVariables
       self.uprn = nil
     end
 
-    if uprn_confirmed&.zero?
+    if uprn_known == 1 && uprn_confirmed&.zero?
       self.uprn = nil
       self.uprn_known = 0
+      self.uprn_confirmed = nil
+      self.address_line1 = nil
+      self.address_line2 = nil
+      self.town_or_city = nil
+      self.county = nil
+      self.postcode_known = nil
+      self.postcode_full = nil
+      self.la = nil
     end
 
     self.nationality_all = nationality_all_group if nationality_uk_or_prefers_not_to_say?
diff --git a/app/models/derived_variables/sales_log_variables.rb b/app/models/derived_variables/sales_log_variables.rb
index cb49b6cc2..05210830b 100644
--- a/app/models/derived_variables/sales_log_variables.rb
+++ b/app/models/derived_variables/sales_log_variables.rb
@@ -45,9 +45,17 @@ module DerivedVariables::SalesLogVariables
       self.uprn = nil
     end
 
-    if uprn_confirmed&.zero?
+    if uprn_known == 1 && uprn_confirmed&.zero?
       self.uprn = nil
       self.uprn_known = 0
+      self.uprn_confirmed = nil
+      self.address_line1 = nil
+      self.address_line2 = nil
+      self.town_or_city = nil
+      self.county = nil
+      self.pcodenk = nil
+      self.postcode_full = nil
+      self.la = nil
     end
 
     self.nationality_all = nationality_all_group if nationality_uk_or_prefers_not_to_say?
diff --git a/spec/shared/shared_examples_for_derived_fields.rb b/spec/shared/shared_examples_for_derived_fields.rb
index 6382ef4f4..3e6b685df 100644
--- a/spec/shared/shared_examples_for_derived_fields.rb
+++ b/spec/shared/shared_examples_for_derived_fields.rb
@@ -14,4 +14,22 @@ RSpec.shared_examples "shared examples for derived fields" do |log_type|
       expect { log.set_derived_fields! }.not_to change(log, :ethnic)
     end
   end
+
+  context "when uprn is not confirmed" do
+    it "derives other uprn fields correctly" do
+      log = FactoryBot.build(log_type, uprn_known: 1, uprn: 1, uprn_confirmed: 0)
+
+      expect { log.set_derived_fields! }.to change(log, :uprn_known).from(1).to(0)
+                                        .and change(log, :uprn).from("1").to(nil)
+                                        .and change(log, :uprn_confirmed).from(0).to(nil)
+    end
+
+    it "does not affect older logs with uprn_confirmed == 0" do
+      log = FactoryBot.build(log_type, uprn_known: 0, uprn: nil, uprn_confirmed: 0)
+
+      expect { log.set_derived_fields! }.to not_change(log, :uprn_known)
+                                        .and not_change(log, :uprn)
+                                        .and not_change(log, :uprn_confirmed)
+    end
+  end
 end