diff --git a/app/controllers/test_data_controller.rb b/app/controllers/test_data_controller.rb
index 8617ff3b5..93361bfcf 100644
--- a/app/controllers/test_data_controller.rb
+++ b/app/controllers/test_data_controller.rb
@@ -1,4 +1,6 @@
 class TestDataController < ApplicationController
+  include CollectionTimeHelper
+
   rescue_from ActiveRecord::RecordNotFound, with: :render_not_found
 
   def create_test_lettings_log
@@ -20,7 +22,7 @@ class TestDataController < ApplicationController
       return render_not_found unless FeatureToggle.create_test_logs_enabled?
 
       file = Tempfile.new("#{year}_test_lettings_log.csv")
-      log = FactoryBot.create(:lettings_log, :completed, assigned_to: current_user, ppostcode_full: "SW1A 1AA", startdate: Time.zone.local(year.to_i, rand(4..12), rand(1..28)))
+      log = FactoryBot.create(:lettings_log, :completed, assigned_to: current_user, ppostcode_full: "SW1A 1AA", startdate: generate_different_date_within_collection_year(Time.zone.local(year.to_i, 4, 1), end_date_override: Time.zone.now + 14.days))
       log_to_csv = BulkUpload::LettingsLogToCsv.new(log:, line_ending: "\n", overrides: { organisation_id: "ORG#{log.owning_organisation_id}", managing_organisation_id: "ORG#{log.owning_organisation_id}" })
       file.write(log_to_csv.default_field_numbers_row)
       file.write(log_to_csv.to_csv_row)
@@ -51,12 +53,12 @@ class TestDataController < ApplicationController
     redirect_to sales_log_path(log)
   end
 
-  [2024, 2025].each do |year|
+  %w[2024 2025].each do |year|
     define_method("create_#{year}_test_sales_bulk_upload") do
       return render_not_found unless FeatureToggle.create_test_logs_enabled?
 
       file = Tempfile.new("#{year}_test_sales_log.csv")
-      log = FactoryBot.create(:sales_log, :completed, assigned_to: current_user, value: 180_000, deposit: 150_000, county: "Somerset", saledate: Time.zone.local(year.to_i, rand(4..12), rand(1..28)))
+      log = FactoryBot.create(:sales_log, :completed, assigned_to: current_user, value: 180_000, deposit: 150_000, county: "Somerset", saledate: generate_different_date_within_collection_year(Time.zone.local(year.to_i, 4, 1), end_date_override: Time.zone.now + 14.days))
       log_to_csv = BulkUpload::SalesLogToCsv.new(log:, line_ending: "\n", overrides: { organisation_id: "ORG#{log.owning_organisation_id}", managing_organisation_id: "ORG#{log.owning_organisation_id}" })
       file.write(log_to_csv.default_field_numbers_row)
       file.write(log_to_csv.to_csv_row)
diff --git a/app/helpers/collection_time_helper.rb b/app/helpers/collection_time_helper.rb
index f5ffd66bf..05fe44449 100644
--- a/app/helpers/collection_time_helper.rb
+++ b/app/helpers/collection_time_helper.rb
@@ -58,7 +58,7 @@ module CollectionTimeHelper
     start_date = [start_date_override, collection_start_date(date).to_date].compact.max.to_date
     end_date = [end_date_override, collection_end_date(date).to_date].compact.min.to_date
 
-    return nil if start_date > end_date
+    return nil if start_date >= end_date
 
     available_dates = (start_date..end_date).to_a - [date.to_date]
     available_dates.empty? ? nil : available_dates.sample
diff --git a/spec/helpers/collection_time_helper_spec.rb b/spec/helpers/collection_time_helper_spec.rb
index a23fc905d..cd1230c85 100644
--- a/spec/helpers/collection_time_helper_spec.rb
+++ b/spec/helpers/collection_time_helper_spec.rb
@@ -106,4 +106,112 @@ RSpec.describe CollectionTimeHelper do
       end
     end
   end
+
+  describe "#generate_different_date_within_collection_year" do
+    let(:date) { Time.zone.local(2024, 6, 15) }
+
+    context "when no overrides are provided" do
+      it "returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date)
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when start_date_override is the last day" do
+      it "returns nil" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2025, 3, 31))
+        expect(result).to be_nil
+      end
+    end
+
+    context "when end_date_override is the first day" do
+      it "returns nil" do
+        result = generate_different_date_within_collection_year(date, end_date_override: Time.zone.local(2024, 4, 1))
+        expect(result).to be_nil
+      end
+    end
+
+    context "when start_date_override and end_date_override are the same day" do
+      it "returns nil" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2024, 6, 15), end_date_override: Time.zone.local(2024, 6, 15))
+        expect(result).to be_nil
+      end
+    end
+
+    context "when start_date_override is greater than end_date_override" do
+      it "returns nil" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2024, 7, 1), end_date_override: Time.zone.local(2024, 6, 1))
+        expect(result).to be_nil
+      end
+    end
+
+    context "when the date is at the start of the collection year" do
+      let(:date) { Time.zone.local(2024, 4, 1) }
+
+      it "returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date)
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when the date is at the end of the collection year" do
+      let(:date) { Time.zone.local(2025, 3, 31) }
+
+      it "returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date)
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when start_date_override is before the collection year" do
+      it "ignores the override and returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2023, 12, 31))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when end_date_override is after the collection year" do
+      it "ignores the override and returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date, end_date_override: Time.zone.local(2025, 12, 1))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when both start_date_override and end_date_override are provided and valid" do
+      it "returns a different date within the overridden range" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2024, 8, 1), end_date_override: Time.zone.local(2024, 9, 1))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 8, 1), Time.zone.local(2024, 9, 1))
+      end
+    end
+
+    context "when both start_date_override and end_date_override are provided but start_date_override is before the collection year" do
+      it "ignores the start_date_override and returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2023, 12, 31), end_date_override: Time.zone.local(2024, 5, 1))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2024, 5, 1))
+      end
+    end
+
+    context "when both start_date_override and end_date_override are provided but end_date_override is after the collection year" do
+      it "ignores the end_date_override and returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2025, 3, 1), end_date_override: Time.zone.local(2025, 12, 1))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2025, 3, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+
+    context "when both start_date_override and end_date_override are outside the collection year" do
+      it "ignores both overrides and returns a different date within the collection year" do
+        result = generate_different_date_within_collection_year(date, start_date_override: Time.zone.local(2023, 12, 31), end_date_override: Time.zone.local(2025, 12, 1))
+        expect(result).not_to eq(date)
+        expect(result).to be_between(Time.zone.local(2024, 4, 1), Time.zone.local(2025, 3, 31))
+      end
+    end
+  end
 end