diff --git a/app/models/forms/bulk_upload_lettings/upload_your_file.rb b/app/models/forms/bulk_upload_lettings/upload_your_file.rb
index 82b5c75d5..552710885 100644
--- a/app/models/forms/bulk_upload_lettings/upload_your_file.rb
+++ b/app/models/forms/bulk_upload_lettings/upload_your_file.rb
@@ -15,6 +15,7 @@ module Forms
 
       validates :file, presence: true
       validate :validate_file_is_csv
+      validate :validate_file_size
 
       def view_path
         "bulk_upload_lettings_logs/forms/upload_your_file"
@@ -73,6 +74,16 @@ module Forms
           errors.add(:file, :not_csv)
         end
       end
+
+      MAX_FILE_SIZE = 10.megabytes
+
+      def validate_file_size
+        return unless file
+
+        if file.size > MAX_FILE_SIZE
+          errors.add(:file, :file_too_large)
+        end
+      end
     end
   end
 end
diff --git a/app/models/forms/bulk_upload_sales/upload_your_file.rb b/app/models/forms/bulk_upload_sales/upload_your_file.rb
index 83ce04e10..447574d1a 100644
--- a/app/models/forms/bulk_upload_sales/upload_your_file.rb
+++ b/app/models/forms/bulk_upload_sales/upload_your_file.rb
@@ -14,6 +14,7 @@ module Forms
 
       validates :file, presence: true
       validate :validate_file_is_csv
+      validate :validate_file_size
 
       def view_path
         "bulk_upload_sales_logs/forms/upload_your_file"
@@ -67,6 +68,16 @@ module Forms
           errors.add(:file, :not_csv)
         end
       end
+
+      MAX_FILE_SIZE = 10.megabytes
+
+      def validate_file_size
+        return unless file
+
+        if file.size > MAX_FILE_SIZE
+          errors.add(:file, :file_too_large)
+        end
+      end
     end
   end
 end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 106ccb9fa..4ef35d19e 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -90,11 +90,13 @@ en:
             file:
               blank: "Select which file to upload."
               not_csv: "Your file must be in CSV format."
+              file_too_large: "File must be 10MB or less. Check your file and delete data that does not need to be uploaded."
         forms/bulk_upload_sales/upload_your_file:
           attributes:
             file:
               blank: "Select which file to upload."
               not_csv: "Your file must be in CSV format."
+              file_too_large: "File must be 10MB or less. Check your file and delete data that does not need to be uploaded."
         forms/bulk_upload_lettings/needstype:
           attributes:
             needstype:
diff --git a/spec/features/bulk_upload_lettings_logs_spec.rb b/spec/features/bulk_upload_lettings_logs_spec.rb
index 315e1461e..b3e403cbf 100644
--- a/spec/features/bulk_upload_lettings_logs_spec.rb
+++ b/spec/features/bulk_upload_lettings_logs_spec.rb
@@ -74,6 +74,25 @@ RSpec.describe "Bulk upload lettings log" do
 
       expect(page).to have_content("Upload lettings logs in bulk")
     end
+
+    it "shows file to large error" do
+      stub_const("Forms::BulkUploadLettings::UploadYourFile::MAX_FILE_SIZE", 1.bytes)
+      visit("/lettings-logs")
+
+      click_link("Upload lettings logs in bulk")
+      expect(page).to have_content("Which year")
+      click_button("Continue")
+      choose(current_formatted_year)
+      click_button("Continue")
+      click_button("Continue")
+
+      allow_any_instance_of(Forms::BulkUploadLettings::UploadYourFile).to receive(:`).and_return("text/csv")
+
+      attach_file "file", file_fixture("2023_24_lettings_bulk_upload.xlsx")
+      click_button("Upload")
+
+      expect(page).to have_content("File must be 10MB or less. Check your file and delete data that does not need to be uploaded.")
+    end
   end
   # rubocop:enable RSpec/AnyInstance
 
diff --git a/spec/features/bulk_upload_sales_logs_spec.rb b/spec/features/bulk_upload_sales_logs_spec.rb
index b7098999d..b32df43e1 100644
--- a/spec/features/bulk_upload_sales_logs_spec.rb
+++ b/spec/features/bulk_upload_sales_logs_spec.rb
@@ -71,6 +71,26 @@ RSpec.describe "Bulk upload sales log" do
 
       expect(page).to have_content("Upload sales logs in bulk")
     end
+
+    it "shows file to large error" do
+      stub_const("Forms::BulkUploadSales::UploadYourFile::MAX_FILE_SIZE", 1.bytes)
+      visit("/sales-logs")
+      click_link("Upload sales logs in bulk")
+
+      expect(page).to have_content("Which year")
+      click_button("Continue")
+      click_button("Continue")
+      choose("2023 to 2024")
+      click_button("Continue")
+      click_button("Continue")
+
+      allow_any_instance_of(Forms::BulkUploadSales::UploadYourFile).to receive(:`).and_return("text/csv")
+
+      attach_file "file", file_fixture("2023_24_lettings_bulk_upload.xlsx")
+      click_button("Upload")
+
+      expect(page).to have_content("File must be 10MB or less. Check your file and delete data that does not need to be uploaded.")
+    end
   end
   # rubocop:enable RSpec/AnyInstance