diff --git a/app/notifications/validators.py b/app/notifications/validators.py
index 4f05977ce..5aee7c55b 100644
--- a/app/notifications/validators.py
+++ b/app/notifications/validators.py
@@ -155,7 +155,7 @@ def check_service_sms_sender_id(service_id, sms_sender_id, notification_type):
             message = 'sms_sender_id is not a valid option for {} notification'.format(notification_type)
             raise BadRequestError(message=message)
         try:
-            dao_get_service_sms_senders_by_id(service_id, sms_sender_id)
+            return dao_get_service_sms_senders_by_id(service_id, sms_sender_id).sms_sender
         except NoResultFound:
             message = 'sms_sender_id {} does not exist in database for service id {}'\
                 .format(sms_sender_id, service_id)
diff --git a/app/v2/notifications/post_notifications.py b/app/v2/notifications/post_notifications.py
index 87d55159d..90cd2997f 100644
--- a/app/v2/notifications/post_notifications.py
+++ b/app/v2/notifications/post_notifications.py
@@ -71,7 +71,7 @@ def post_notification(notification_type):
     check_rate_limiting(authenticated_service, api_user)
 
     check_service_email_reply_to_id(str(authenticated_service.id), service_email_reply_to_id, notification_type)
-    check_service_sms_sender_id(str(authenticated_service.id), service_sms_sender_id, notification_type)
+    sms_sender = check_service_sms_sender_id(str(authenticated_service.id), service_sms_sender_id, notification_type)
 
     template, template_with_content = validate_template(
         form['template_id'],
@@ -98,7 +98,7 @@ def post_notification(notification_type):
     if notification_type == SMS_TYPE:
         create_resp_partial = functools.partial(
             create_post_sms_response_from_notification,
-            from_number=authenticated_service.get_default_sms_sender()
+            from_number=sms_sender or authenticated_service.get_default_sms_sender()
         )
     elif notification_type == EMAIL_TYPE:
         create_resp_partial = functools.partial(
diff --git a/tests/app/notifications/test_validators.py b/tests/app/notifications/test_validators.py
index ede6d940d..a20251790 100644
--- a/tests/app/notifications/test_validators.py
+++ b/tests/app/notifications/test_validators.py
@@ -374,7 +374,7 @@ def test_check_service_sms_sender_id_where_sms_sender_id_is_none(notification_ty
 
 def test_check_service_sms_sender_id_where_sms_sender_id_is_found(sample_service):
     sms_sender = create_service_sms_sender(service=sample_service, sms_sender='123456')
-    assert check_service_sms_sender_id(sample_service.id, sms_sender.id, SMS_TYPE) is None
+    assert check_service_sms_sender_id(sample_service.id, sms_sender.id, SMS_TYPE) == '123456'
 
 
 def test_check_service_sms_sender_id_where_service_id_is_not_found(sample_service, fake_uuid):
diff --git a/tests/app/v2/notifications/test_post_notifications.py b/tests/app/v2/notifications/test_post_notifications.py
index d4055df3f..a1746ae06 100644
--- a/tests/app/v2/notifications/test_post_notifications.py
+++ b/tests/app/v2/notifications/test_post_notifications.py
@@ -118,6 +118,7 @@ def test_post_sms_notification_returns_201_with_sms_sender_id(
     notification_to_sms_sender = NotificationSmsSender.query.all()
     assert len(notification_to_sms_sender) == 1
     assert str(notification_to_sms_sender[0].notification_id) == resp_json['id']
+    assert resp_json['content']['from_number'] == sms_sender.sms_sender
     assert notification_to_sms_sender[0].service_sms_sender_id == sms_sender.id
     mocked.assert_called_once_with([resp_json['id']], queue='send-sms-tasks')