diff --git a/app/dao/notifications_dao.py b/app/dao/notifications_dao.py
index 84f9e1249..8976bbebc 100644
--- a/app/dao/notifications_dao.py
+++ b/app/dao/notifications_dao.py
@@ -689,11 +689,11 @@ def dao_old_letters_with_created_status():
     last_processing_deadline = yesterday_bst.replace(hour=17, minute=30, second=0, microsecond=0)
 
     notifications = Notification.query.filter(
-        Notification.created_at < convert_bst_to_utc(last_processing_deadline),
+        Notification.updated_at < convert_bst_to_utc(last_processing_deadline),
         Notification.notification_type == LETTER_TYPE,
         Notification.status == NOTIFICATION_CREATED
     ).order_by(
-        Notification.created_at
+        Notification.updated_at
     ).all()
     return notifications
 
diff --git a/tests/app/celery/test_scheduled_tasks.py b/tests/app/celery/test_scheduled_tasks.py
index baf108380..f6081916f 100644
--- a/tests/app/celery/test_scheduled_tasks.py
+++ b/tests/app/celery/test_scheduled_tasks.py
@@ -376,12 +376,12 @@ def test_check_templated_letter_state_during_bst(mocker, sample_letter_template)
     mock_logger = mocker.patch('app.celery.tasks.current_app.logger.exception')
     mock_create_ticket = mocker.patch('app.celery.nightly_tasks.zendesk_client.create_ticket')
 
-    noti_1 = create_notification(template=sample_letter_template, created_at=datetime(2019, 5, 1, 12, 0))
-    noti_2 = create_notification(template=sample_letter_template, created_at=datetime(2019, 5, 29, 16, 29))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 5, 29, 16, 30))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 5, 29, 17, 29))
-    create_notification(template=sample_letter_template, status='delivered', created_at=datetime(2019, 5, 28, 10, 0))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 5, 30, 10, 0))
+    noti_1 = create_notification(template=sample_letter_template, updated_at=datetime(2019, 5, 1, 12, 0))
+    noti_2 = create_notification(template=sample_letter_template, updated_at=datetime(2019, 5, 29, 16, 29))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 5, 29, 16, 30))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 5, 29, 17, 29))
+    create_notification(template=sample_letter_template, status='delivered', updated_at=datetime(2019, 5, 28, 10, 0))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 5, 30, 10, 0))
 
     check_templated_letter_state()
 
@@ -401,12 +401,12 @@ def test_check_templated_letter_state_during_utc(mocker, sample_letter_template)
     mock_logger = mocker.patch('app.celery.tasks.current_app.logger.exception')
     mock_create_ticket = mocker.patch('app.celery.nightly_tasks.zendesk_client.create_ticket')
 
-    noti_1 = create_notification(template=sample_letter_template, created_at=datetime(2018, 12, 1, 12, 0))
-    noti_2 = create_notification(template=sample_letter_template, created_at=datetime(2019, 1, 29, 17, 29))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 1, 29, 17, 30))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 1, 29, 18, 29))
-    create_notification(template=sample_letter_template, status='delivered', created_at=datetime(2019, 1, 29, 10, 0))
-    create_notification(template=sample_letter_template, created_at=datetime(2019, 1, 30, 10, 0))
+    noti_1 = create_notification(template=sample_letter_template, updated_at=datetime(2018, 12, 1, 12, 0))
+    noti_2 = create_notification(template=sample_letter_template, updated_at=datetime(2019, 1, 29, 17, 29))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 1, 29, 17, 30))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 1, 29, 18, 29))
+    create_notification(template=sample_letter_template, status='delivered', updated_at=datetime(2019, 1, 29, 10, 0))
+    create_notification(template=sample_letter_template, updated_at=datetime(2019, 1, 30, 10, 0))
 
     check_templated_letter_state()