diff --git a/app/celery/letters_pdf_tasks.py b/app/celery/letters_pdf_tasks.py
index 409ed7808..d50c5b42c 100644
--- a/app/celery/letters_pdf_tasks.py
+++ b/app/celery/letters_pdf_tasks.py
@@ -120,7 +120,8 @@ def collate_letter_pdfs_for_day(date=None):
         subfolder=date
     )
     for i, letters in enumerate(group_letters(letter_pdfs)):
-        dvla_filename = 'NOTIFY.{date}{num:06}.ZIP'.format(date=date.replace('-', ''), num=i + 1)
+        # eg NOTIFY.2018-12-31.001.ZIP
+        dvla_filename = 'NOTIFY.{date}.{num:03}.ZIP'.format(date=date, num=i + 1)
         filenames = [letter['Key'] for letter in letters]
         current_app.logger.info(
             'Calling task zip-and-send-letter-pdfs for {} pdfs to upload {} with total size {:,} bytes'.format(
diff --git a/tests/app/celery/test_letters_pdf_tasks.py b/tests/app/celery/test_letters_pdf_tasks.py
index d35301ae5..4cc8d0dbd 100644
--- a/tests/app/celery/test_letters_pdf_tasks.py
+++ b/tests/app/celery/test_letters_pdf_tasks.py
@@ -231,13 +231,13 @@ def test_collate_letter_pdfs_for_day(notify_api, mocker):
     mock_group_letters.assert_called_once_with(mock_s3.return_value)
     assert mock_celery.call_args_list[0] == call(
         name='zip-and-send-letter-pdfs',
-        kwargs={'filenames_to_zip': ['A.PDF', 'B.pDf'], 'upload_filename': 'NOTIFY.20170102000001.ZIP'},
+        kwargs={'filenames_to_zip': ['A.PDF', 'B.pDf'], 'upload_filename': 'NOTIFY.2017-01-02.001.ZIP'},
         queue='process-ftp-tasks',
         compression='zlib'
     )
     assert mock_celery.call_args_list[1] == call(
         name='zip-and-send-letter-pdfs',
-        kwargs={'filenames_to_zip': ['C.pdf'], 'upload_filename': 'NOTIFY.20170102000002.ZIP'},
+        kwargs={'filenames_to_zip': ['C.pdf'], 'upload_filename': 'NOTIFY.2017-01-02.002.ZIP'},
         queue='process-ftp-tasks',
         compression='zlib'
     )