diff --git a/app/celery/tasks.py b/app/celery/tasks.py
index 7287118a4..a1ee49020 100644
--- a/app/celery/tasks.py
+++ b/app/celery/tasks.py
@@ -18,7 +18,6 @@ from requests import (
     RequestException
 )
 from sqlalchemy.exc import SQLAlchemyError
-from sqlalchemy.orm.exc import NoResultFound
 
 from app import (
     create_uuid,
@@ -42,7 +41,6 @@ from app.dao.notifications_dao import (
     dao_get_last_notification_added_for_job_id,
     update_notification_status_by_reference,
     dao_get_notification_history_by_reference,
-    dao_get_notification_by_reference,
 )
 from app.dao.provider_details_dao import get_current_provider
 from app.dao.service_email_reply_to_dao import dao_get_reply_to_by_id
@@ -498,12 +496,7 @@ def update_letter_notification(filename, temporary_failures, update):
 
 
 def check_billable_units(notification_update):
-    try:
-        # This try except is necessary because in test keys and research mode does not create notification history.
-        # Otherwise we could just search for the NotificationHistory object
-        notification = dao_get_notification_by_reference(notification_update.reference)
-    except NoResultFound:
-        notification = dao_get_notification_history_by_reference(notification_update.reference)
+    notification = dao_get_notification_history_by_reference(notification_update.reference)
 
     if int(notification_update.page_count) != notification.billable_units:
         msg = 'Notification with id {} has {} billable_units but DVLA says page count is {}'.format(
diff --git a/app/dao/notifications_dao.py b/app/dao/notifications_dao.py
index 35d5759e4..bcd5a5668 100644
--- a/app/dao/notifications_dao.py
+++ b/app/dao/notifications_dao.py
@@ -17,6 +17,7 @@ from notifications_utils.statsd_decorators import statsd
 from notifications_utils.timezones import convert_utc_to_bst
 from sqlalchemy import (desc, func, asc)
 from sqlalchemy.orm import joinedload
+from sqlalchemy.orm.exc import NoResultFound
 from sqlalchemy.sql import functions
 from sqlalchemy.sql.expression import case
 from sqlalchemy.dialects.postgresql import insert
@@ -585,9 +586,16 @@ def dao_get_notification_by_reference(reference):
 
 @statsd(namespace="dao")
 def dao_get_notification_history_by_reference(reference):
-    return NotificationHistory.query.filter(
-        NotificationHistory.reference == reference
-    ).one()
+    try:
+        # This try except is necessary because in test keys and research mode does not create notification history.
+        # Otherwise we could just search for the NotificationHistory object
+        return Notification.query.filter(
+            Notification.reference == reference
+        ).one()
+    except NoResultFound:
+        return NotificationHistory.query.filter(
+            NotificationHistory.reference == reference
+        ).one()
 
 
 @statsd(namespace="dao")
diff --git a/migrations/versions/0293_drop_complaint_fk.py b/migrations/versions/0293_drop_complaint_fk.py
new file mode 100644
index 000000000..84d431f15
--- /dev/null
+++ b/migrations/versions/0293_drop_complaint_fk.py
@@ -0,0 +1,21 @@
+"""
+
+Revision ID: 0293_drop_complaint_fk
+Revises: 0292_give_users_folder_perms
+Create Date: 2019-05-16 14:05:18.104274
+
+"""
+from alembic import op
+
+
+revision = '0293_drop_complaint_fk'
+down_revision = '0292_give_users_folder_perms'
+
+
+def upgrade():
+    op.drop_constraint('complaints_notification_id_fkey', table_name='complaints', type_='foreignkey')
+
+
+def downgrade():
+    op.create_foreign_key('complaints_notification_id_fkey', 'complaints',
+                          'notification_history', ['notification_id'], ['id'])
diff --git a/tests/app/dao/test_provider_details_dao.py b/tests/app/dao/test_provider_details_dao.py
index 31a058831..153f39a2e 100644
--- a/tests/app/dao/test_provider_details_dao.py
+++ b/tests/app/dao/test_provider_details_dao.py
@@ -262,7 +262,7 @@ def test_toggle_sms_provider_switches_provider_stores_notify_user_id_in_history(
     assert old_provider_from_history.created_by_id == sample_user.id
 
 
-def test_can_get_all_provider_history(current_sms_provider):
+def test_can_get_all_provider_history(restore_provider_details, current_sms_provider):
     assert len(dao_get_provider_versions(current_sms_provider.id)) == 1