diff --git a/app/service/rest.py b/app/service/rest.py
index 4416a5a39..0643d3108 100644
--- a/app/service/rest.py
+++ b/app/service/rest.py
@@ -12,6 +12,7 @@ from notifications_utils.timezones import convert_utc_to_bst
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm.exc import NoResultFound
 
+from app import DATE_FORMAT
 from app.config import QueueNames
 from app.dao import fact_notification_status_dao, notifications_dao
 from app.dao.dao_utils import dao_rollback
@@ -946,6 +947,8 @@ def check_if_reply_to_address_already_in_use(service_id, email_address):
 def returned_letter_summary(service_id):
     results = get_returned_letter_summary(service_id)
 
-    json_results = [{'returned_letter_count': x.returned_letter_count, 'reported_at': x.reported_at} for x in results]
+    json_results = [{'returned_letter_count': x.returned_letter_count,
+                     'reported_at': x.reported_at.strftime(DATE_FORMAT)
+                     } for x in results]
 
     return jsonify(json_results)
diff --git a/tests/app/dao/test_returned_letters_dao.py b/tests/app/dao/test_returned_letters_dao.py
index bb0836be0..9c33988a4 100644
--- a/tests/app/dao/test_returned_letters_dao.py
+++ b/tests/app/dao/test_returned_letters_dao.py
@@ -50,7 +50,7 @@ def test_insert_or_update_returned_letters_updates(sample_letter_template):
             assert x.notification_id in [notification.id, history.id]
 
 
-def test_insert_or_update_returned_letters_when_no_notification(sample_letter_template):
+def test_insert_or_update_returned_letters_when_no_notification(notify_db_session):
     insert_or_update_returned_letters(['ref1'])
     assert ReturnedLetter.query.count() == 0
 
@@ -104,6 +104,7 @@ def test_get_returned_letter_summary_orders_by_reported_at(sample_service):
     create_returned_letter(sample_service, reported_at=now)
     create_returned_letter(sample_service, reported_at=last_month)
     create_returned_letter(sample_service, reported_at=last_month)
+    create_returned_letter()  # returned letter for a different service
 
     results = get_returned_letter_summary(sample_service.id)
 
diff --git a/tests/app/db.py b/tests/app/db.py
index ac23654c2..e95f79b77 100644
--- a/tests/app/db.py
+++ b/tests/app/db.py
@@ -944,7 +944,7 @@ def set_up_usage_data(start_date):
     return org, org_3, service, service_3, service_4, service_sms_only
 
 
-def create_returned_letter(service, reported_at=None):
+def create_returned_letter(service=None, reported_at=None):
     if not service:
         service = create_service(service_name='a - with sms and letter')
     template = create_template(service=service, template_type=LETTER_TYPE)
diff --git a/tests/app/service/test_rest.py b/tests/app/service/test_rest.py
index 316819da0..ec736abd1 100644
--- a/tests/app/service/test_rest.py
+++ b/tests/app/service/test_rest.py
@@ -3374,10 +3374,14 @@ def test_get_monthly_notification_data_by_service(mocker, admin_request):
     assert response == []
 
 
+@freeze_time('2019-12-11 13:30')
 def test_get_returned_letter_summary(admin_request, sample_service):
-    create_returned_letter(sample_service, reported_at=datetime.utcnow())
     create_returned_letter(sample_service, reported_at=datetime.utcnow() - timedelta(days=3))
+    create_returned_letter(sample_service, reported_at=datetime.utcnow())
+    create_returned_letter(sample_service, reported_at=datetime.utcnow())
 
     response = admin_request.get('service.returned_letter_summary', service_id=sample_service.id)
 
     assert len(response) == 2
+    assert response[0] == {'returned_letter_count': 2, 'reported_at': '2019-12-11'}
+    assert response[1] == {'returned_letter_count': 1, 'reported_at': '2019-12-08'}