diff --git a/app/services/imports/lettings_logs_field_import_service.rb b/app/services/imports/lettings_logs_field_import_service.rb
index f69fe5792..4530b5c38 100644
--- a/app/services/imports/lettings_logs_field_import_service.rb
+++ b/app/services/imports/lettings_logs_field_import_service.rb
@@ -20,6 +20,8 @@ module Imports
         import_from(folder, :update_homelessness)
       when "created_by"
         import_from(folder, :update_created_by)
+      when "sex_and_relat"
+        import_from(folder, :update_sex_and_relat)
       else
         raise "Updating #{field} is not supported by the field import service"
       end
@@ -249,5 +251,35 @@ module Imports
       log_import_service.send(:create_log, xml_doc)
       @logger.info("lettings log \"#{record.old_id}\" has been reimported with id #{record.id}")
     end
+
+    def update_sex_and_relat(xml_doc)
+      return if meta_field_value(xml_doc, "form-name").include?("Sales")
+
+      old_id = meta_field_value(xml_doc, "document-id")
+      record = LettingsLog.find_by(old_id:)
+
+      return @logger.warn("lettings log with old id #{old_id} not found") unless record
+      return @logger.info("lettings log #{record.id} has no hhmemb value, skipping update") if record.hhmemb.blank?
+
+      (2..record.hhmemb).each do |i|
+        next @logger.info("lettings log #{record.id} has values for sex#{i} and relat#{i}, skipping update") if record["sex#{i}"] && record["relat#{i}"]
+        next @logger.info("lettings log #{record.id} has value 'no' for details_known_#{i}, skipping update") if record["details_known_#{i}"] == 1
+
+        if record["sex#{i}"].blank?
+          record["sex#{i}"] = sex(xml_doc, i)
+          @logger.info("lettings log #{record.id}'s sex#{i} value has been set to #{record["sex#{i}"]}")
+        end
+
+        if record["relat#{i}"].blank?
+          record["relat#{i}"] = relat(xml_doc, i)
+          @logger.info("lettings log #{record.id}'s relat#{i} value has been set to #{record["relat#{i}"]}")
+        end
+      end
+
+      if record.changed?
+        record.values_updated_at = Time.zone.now
+        record.save!
+      end
+    end
   end
 end
diff --git a/lib/tasks/data_import_field.rake b/lib/tasks/data_import_field.rake
index 478c1f59b..db80d9af4 100644
--- a/lib/tasks/data_import_field.rake
+++ b/lib/tasks/data_import_field.rake
@@ -7,7 +7,7 @@ namespace :core do
 
     # We only allow a reduced list of known fields to be updatable
     case field
-    when "tenancycode", "major_repairs", "lettings_allocation", "offered", "address", "reason", "homeless", "created_by"
+    when "tenancycode", "major_repairs", "lettings_allocation", "offered", "address", "reason", "homeless", "created_by", "sex_and_relat"
       s3_service = Storage::S3Service.new(PlatformHelper.is_paas? ? Configuration::PaasConfigurationService.new : Configuration::EnvConfigurationService.new, ENV["IMPORT_PAAS_INSTANCE"])
       archive_io = s3_service.get_file_io(path)
       archive_service = Storage::ArchiveService.new(archive_io)
diff --git a/spec/lib/tasks/data_import_field_spec.rb b/spec/lib/tasks/data_import_field_spec.rb
index c8d1dd056..de527062b 100644
--- a/spec/lib/tasks/data_import_field_spec.rb
+++ b/spec/lib/tasks/data_import_field_spec.rb
@@ -140,6 +140,18 @@ describe "data_import_field imports" do
         end
       end
 
+      context "and we update the sex_and_relat fields" do
+        let(:field) { "sex_and_relat" }
+
+        it "updates the 2023 logs from the given XML file" do
+          expect(Storage::S3Service).to receive(:new).with(paas_config_service, instance_name)
+          expect(storage_service).to receive(:get_file_io).with("spec/fixtures/imports/logs")
+          expect(Imports::LettingsLogsFieldImportService).to receive(:new).with(archive_service)
+          expect(import_service).to receive(:update_field).with(field, "logs")
+          task.invoke(field, fixture_path)
+        end
+      end
+
       it "raises an exception if no parameters are provided" do
         expect { task.invoke }.to raise_error(/Usage/)
       end
diff --git a/spec/services/imports/lettings_logs_field_import_service_spec.rb b/spec/services/imports/lettings_logs_field_import_service_spec.rb
index 669482b8a..782ce86c8 100644
--- a/spec/services/imports/lettings_logs_field_import_service_spec.rb
+++ b/spec/services/imports/lettings_logs_field_import_service_spec.rb
@@ -779,4 +779,162 @@ RSpec.describe Imports::LettingsLogsFieldImportService do
       end
     end
   end
+
+  context "when updating sex_and_relat" do
+    let(:field) { "sex_and_relat" }
+    let(:lettings_log) { LettingsLog.find_by(old_id: lettings_log_id) }
+
+    before do
+      Imports::LettingsLogsImportService.new(storage_service, logger).create_logs(fixture_directory)
+      lettings_log_file.rewind
+      lettings_log_xml.at_xpath("//xmlns:P2Sex").content = "Person prefers not to say"
+      lettings_log_xml.at_xpath("//xmlns:P2Rel").content = "Person prefers not to say"
+    end
+
+    context "when the lettings log has no sex or relat value" do
+      before do
+        lettings_log.update!(sex2: nil, relat2: nil, details_known_2: 0, values_updated_at: nil)
+      end
+
+      it "updates the lettings_log sex and relat value if details for person are known" do
+        expect(logger).to receive(:info).with(/lettings log \d+'s sex2 value has been set to R/)
+        expect(logger).to receive(:info).with(/lettings log \d+'s relat2 value has been set to R/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq("R")
+        expect(lettings_log.relat2).to eq("R")
+        expect(lettings_log.values_updated_at).not_to be_nil
+      end
+
+      it "does not update the lettings_log sex and relat value if details for person are not known" do
+        lettings_log.update!(details_known_2: 1)
+
+        expect(logger).to receive(:info).with(/lettings log \d+ has value 'no' for details_known_2, skipping update/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq(nil)
+        expect(lettings_log.relat2).to eq(nil)
+        expect(lettings_log.values_updated_at).to be_nil
+      end
+    end
+
+    context "when the lettings log has sex and relat value" do
+      before do
+        lettings_log.update!(sex2: "F", relat2: "R", details_known_2: 0, values_updated_at: nil)
+      end
+
+      it "does not update the lettings_log sex and relat values" do
+        expect(logger).to receive(:info).with(/lettings log \d+ has values for sex2 and relat2, skipping update/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq("F")
+        expect(lettings_log.relat2).to eq("R")
+        expect(lettings_log.values_updated_at).to be_nil
+      end
+    end
+
+    context "when the lettings log has sex value" do
+      before do
+        lettings_log.update!(sex2: "F", relat2: nil, details_known_2: 0, values_updated_at: nil)
+      end
+
+      it "only updates relat value" do
+        expect(logger).to receive(:info).with(/lettings log \d+'s relat2 value has been set to R/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq("F")
+        expect(lettings_log.relat2).to eq("R")
+        expect(lettings_log.values_updated_at).not_to be_nil
+      end
+    end
+
+    context "when the lettings log has relat value" do
+      before do
+        lettings_log.update!(sex2: nil, relat2: "X", details_known_2: 0, values_updated_at: nil)
+      end
+
+      it "only updates sex value" do
+        expect(logger).to receive(:info).with(/lettings log \d+'s sex2 value has been set to R/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq("R")
+        expect(lettings_log.relat2).to eq("X")
+        expect(lettings_log.values_updated_at).not_to be_nil
+      end
+    end
+
+    context "when the lettings log has no hhmemb value" do
+      before do
+        lettings_log.update!(sex2: nil, relat2: nil, hhmemb: nil, values_updated_at: nil)
+      end
+
+      it "does not update the lettings_log sex and relat values" do
+        expect(logger).to receive(:info).with(/lettings log \d+ has no hhmemb value, skipping update/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq(nil)
+        expect(lettings_log.relat2).to eq(nil)
+        expect(lettings_log.values_updated_at).to be_nil
+      end
+    end
+
+    context "when there are multiple people details given" do
+      before do
+        (2..8).each do |i|
+          lettings_log_xml.at_xpath("//xmlns:P#{i}Sex").content = "Person prefers not to say"
+          lettings_log_xml.at_xpath("//xmlns:P#{i}Rel").content = "Person prefers not to say"
+        end
+      end
+
+      it "correctly skips and sets sex and relat values" do
+        lettings_log.update!(sex2: "F", relat2: "X", details_known_2: 0,
+                             sex3: nil, relat3: nil, details_known_3: 0,
+                             sex4: "F", relat4: nil, details_known_4: 0,
+                             sex5: nil, relat5: "X", details_known_5: 0,
+                             sex6: nil, relat6: nil, details_known_6: 1,
+                             hhmemb: 6, values_updated_at: nil)
+
+        expect(logger).to receive(:info).with(/lettings log \d+ has values for sex2 and relat2, skipping update/)
+        expect(logger).to receive(:info).with(/lettings log \d+'s sex3 value has been set to R/)
+        expect(logger).to receive(:info).with(/lettings log \d+'s relat3 value has been set to R/)
+        expect(logger).to receive(:info).with(/lettings log \d+'s relat4 value has been set to R/)
+        expect(logger).to receive(:info).with(/lettings log \d+'s sex5 value has been set to R/)
+        expect(logger).to receive(:info).with(/lettings log \d+ has value 'no' for details_known_6, skipping update/)
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+
+        lettings_log.reload
+        expect(lettings_log.sex2).to eq("F")
+        expect(lettings_log.relat2).to eq("X")
+        expect(lettings_log.sex3).to eq("R")
+        expect(lettings_log.relat3).to eq("R")
+        expect(lettings_log.sex4).to eq("F")
+        expect(lettings_log.relat4).to eq("R")
+        expect(lettings_log.sex5).to eq("R")
+        expect(lettings_log.relat5).to eq("X")
+        expect(lettings_log.sex6).to eq(nil)
+        expect(lettings_log.relat6).to eq(nil)
+        expect(lettings_log.sex7).to eq(nil)
+        expect(lettings_log.relat7).to eq(nil)
+        expect(lettings_log.sex8).to eq(nil)
+        expect(lettings_log.relat8).to eq(nil)
+        expect(lettings_log.values_updated_at).not_to be_nil
+      end
+
+      it "correctly skips the entire update if none of the fields need to be updated" do
+        lettings_log.update!(sex2: "F", relat2: "X", details_known_2: 0,
+                             sex3: nil, relat3: nil, details_known_3: 1,
+                             sex4: "F", relat4: "X", details_known_4: 0,
+                             sex5: nil, relat5: nil, details_known_5: 1,
+                             hhmemb: 5, values_updated_at: nil)
+
+        expect(logger).to receive(:info).with(/lettings log \d+ has values for sex2 and relat2, skipping update/)
+        expect(logger).to receive(:info).with(/lettings log \d+ has value 'no' for details_known_3, skipping update/)
+        expect(logger).to receive(:info).with(/lettings log \d+ has values for sex4 and relat4, skipping update/)
+        expect(logger).to receive(:info).with(/lettings log \d+ has value 'no' for details_known_5, skipping update/)
+
+        import_service.send(:update_sex_and_relat, lettings_log_xml)
+        expect(lettings_log.values_updated_at).to be_nil
+      end
+    end
+  end
 end