diff --git a/app/models/derived_variables/lettings_log_variables.rb b/app/models/derived_variables/lettings_log_variables.rb
index 960ecad52..ab604ea40 100644
--- a/app/models/derived_variables/lettings_log_variables.rb
+++ b/app/models/derived_variables/lettings_log_variables.rb
@@ -186,7 +186,7 @@ private
   end
 
   def get_refused
-    return 1 if age_refused? || sex_refused? || relat_refused? || ecstat_refused?
+    return 1 if details_unknown? || age_refused? || sex_refused? || relat_refused? || ecstat_refused?
 
     0
   end
diff --git a/app/models/lettings_log.rb b/app/models/lettings_log.rb
index 45d13a792..79a6837d3 100644
--- a/app/models/lettings_log.rb
+++ b/app/models/lettings_log.rb
@@ -703,6 +703,10 @@ private
     [ecstat1, ecstat2, ecstat3, ecstat4, ecstat5, ecstat6, ecstat7, ecstat8].any?(10)
   end
 
+  def details_unknown?
+    [details_known_2, details_known_3, details_known_4, details_known_5, details_known_6, details_known_7, details_known_8].any?(1)
+  end
+
   def soft_value_for_period(value)
     num_of_weeks = NUM_OF_WEEKS_FROM_PERIOD[period]
     return "" unless value && num_of_weeks
diff --git a/app/services/exports/lettings_log_export_service.rb b/app/services/exports/lettings_log_export_service.rb
index 9bcc8676c..bff076908 100644
--- a/app/services/exports/lettings_log_export_service.rb
+++ b/app/services/exports/lettings_log_export_service.rb
@@ -210,6 +210,17 @@ module Exports
         add_location_fields!(lettings_log.location, attribute_hash) if lettings_log.location
         attribute_hash.delete("unittype_gn")
       end
+
+      # details unknown fields
+      (2..8).each do |index|
+        next unless lettings_log["details_known_#{index}"] == 1
+
+        attribute_hash["age#{index}"] = -9
+        attribute_hash["sex#{index}"] = "R"
+        attribute_hash["relat#{index}"] = "R"
+        attribute_hash["ecstat#{index}"] = 10
+      end
+
       attribute_hash
     end
 
diff --git a/spec/models/lettings_log_spec.rb b/spec/models/lettings_log_spec.rb
index 74a04f9e6..f2700138c 100644
--- a/spec/models/lettings_log_spec.rb
+++ b/spec/models/lettings_log_spec.rb
@@ -1810,22 +1810,41 @@ RSpec.describe LettingsLog do
     end
 
     context "when answering the household characteristics questions" do
-      let!(:lettings_log) do
-        described_class.create({
-          managing_organisation: owning_organisation,
-          owning_organisation:,
-          created_by: created_by_user,
-          age1_known: 1,
-          sex1: "R",
-          relat2: "R",
-          ecstat1: 10,
-        })
+      context "and some person details are refused" do
+        let!(:lettings_log) do
+          described_class.create({
+            managing_organisation: owning_organisation,
+            owning_organisation:,
+            created_by: created_by_user,
+            age1_known: 1,
+            sex1: "R",
+            relat2: "R",
+            ecstat1: 10,
+          })
+        end
+
+        it "correctly derives and saves refused" do
+          record_from_db = described_class.find(lettings_log.id)
+          expect(record_from_db["refused"]).to eq(1)
+          expect(lettings_log["refused"]).to eq(1)
+        end
       end
 
-      it "correctly derives and saves refused" do
-        record_from_db = described_class.find(lettings_log.id)
-        expect(record_from_db["refused"]).to eq(1)
-        expect(lettings_log["refused"]).to eq(1)
+      context "and some person details are not known" do
+        let!(:lettings_log) do
+          described_class.create({
+            managing_organisation: owning_organisation,
+            owning_organisation:,
+            created_by: created_by_user,
+            details_known_2: 1,
+          })
+        end
+
+        it "correctly derives and saves refused" do
+          record_from_db = described_class.find(lettings_log.id)
+          expect(record_from_db["refused"]).to eq(1)
+          expect(lettings_log["refused"]).to eq(1)
+        end
       end
     end
 
diff --git a/spec/services/exports/lettings_log_export_service_spec.rb b/spec/services/exports/lettings_log_export_service_spec.rb
index 7b9f55b93..5402c19db 100644
--- a/spec/services/exports/lettings_log_export_service_spec.rb
+++ b/spec/services/exports/lettings_log_export_service_spec.rb
@@ -150,6 +150,32 @@ RSpec.describe Exports::LettingsLogExportService do
       end
     end
 
+    context "and one lettings log with unknown user details is available for export" do
+      let!(:lettings_log) { FactoryBot.create(:lettings_log, :completed, details_known_2: 1, created_by: user, propcode: "123", ppostcode_full: "SE2 6RT", postcode_full: "NW1 5TY", tenancycode: "BZ737", startdate: Time.zone.local(2022, 2, 2, 10, 36, 49), voiddate: Time.zone.local(2019, 11, 3), mrcdate: Time.zone.local(2020, 5, 5, 10, 36, 49), tenancylength: 5, underoccupation_benefitcap: 4) }
+
+      def replace_person_details(export_file)
+        export_file.sub!("<age2>32</age2>", "<age2>-9</age2>")
+        export_file.sub!("<ecstat2>6</ecstat2>", "<ecstat2>10</ecstat2>")
+        export_file.sub!("<sex2>M</sex2>", "<sex2>R</sex2>")
+        export_file.sub!("<relat2>P</relat2>", "<relat2>R</relat2>")
+        export_file.sub!("<refused>0</refused>", "<refused>1</refused>")
+        export_file.sub!("<hhtype>4</hhtype>", "<hhtype>3</hhtype>")
+        export_file.sub!("<totadult>2</totadult>", "<totadult>1</totadult>")
+      end
+
+      it "generates an XML export file with the expected content within the ZIP file" do
+        expected_content = replace_entity_ids(lettings_log, xml_export_file.read)
+        expected_content = replace_person_details(expected_content)
+        expect(storage_service).to receive(:write_file).with(expected_zip_filename, any_args) do |_, content|
+          entry = Zip::File.open_buffer(content).find_entry(expected_data_filename)
+          expect(entry).not_to be_nil
+          expect(entry.get_input_stream.read).to eq(expected_content)
+        end
+
+        export_service.export_xml_lettings_logs
+      end
+    end
+
     context "with 23/24 collection period" do
       before do
         Timecop.freeze(Time.zone.local(2023, 4, 3))