diff --git a/app/main/views/platform_admin.py b/app/main/views/platform_admin.py
index 2598a4eb6..25b727630 100644
--- a/app/main/views/platform_admin.py
+++ b/app/main/views/platform_admin.py
@@ -360,6 +360,9 @@ def platform_admin_returned_letters():
 
         try:
             letter_jobs_client.submit_returned_letters(references)
+            redis_client.delete_cache_keys_by_pattern(
+                'service-????????-????-????-????-????????????-returned-letters-summary'
+            )
         except HTTPError as error:
             if error.status_code == 400:
                 error_references = [
diff --git a/app/notify_client/service_api_client.py b/app/notify_client/service_api_client.py
index eaaf5b59e..b89e5c196 100644
--- a/app/notify_client/service_api_client.py
+++ b/app/notify_client/service_api_client.py
@@ -569,6 +569,7 @@ class ServiceAPIClient(NotifyAdminAPIClient):
     def get_service_data_retention(self, service_id):
         return self.get("/service/{}/data-retention".format(service_id))
 
+    @cache.set('service-{service_id}-returned-letters-summary')
     def get_returned_letter_summary(self, service_id):
         return self.get("service/{}/returned-letter-summary".format(service_id))
 
diff --git a/tests/app/main/views/test_platform_admin.py b/tests/app/main/views/test_platform_admin.py
index cd22eb384..fb13306d1 100644
--- a/tests/app/main/views/test_platform_admin.py
+++ b/tests/app/main/views/test_platform_admin.py
@@ -680,6 +680,7 @@ def test_platform_admin_displays_stats_in_right_boxes_and_with_correct_styling(
 
 def test_platform_admin_submit_returned_letters(mocker, platform_admin_client):
 
+    redis = mocker.patch('app.main.views.platform_admin.redis_client')
     mock_client = mocker.patch('app.letter_jobs_client.submit_returned_letters')
 
     response = platform_admin_client.post(
@@ -688,7 +689,9 @@ def test_platform_admin_submit_returned_letters(mocker, platform_admin_client):
     )
 
     mock_client.assert_called_once_with(['REF1', 'REF2'])
-
+    redis.delete_cache_keys_by_pattern.assert_called_once_with(
+        'service-????????-????-????-????-????????????-returned-letters-summary'
+    )
     assert response.status_code == 302
     assert response.location == url_for('main.platform_admin_returned_letters', _external=True)
 
diff --git a/tests/app/notify_client/test_service_api_client.py b/tests/app/notify_client/test_service_api_client.py
index 1a1ee7c3a..de7e731be 100644
--- a/tests/app/notify_client/test_service_api_client.py
+++ b/tests/app/notify_client/test_service_api_client.py
@@ -316,6 +316,25 @@ def test_client_returns_count_of_service_templates(
             ],
             {'data_from': 'api'},
         ),
+        (
+            service_api_client.get_returned_letter_summary,
+            [SERVICE_ONE_ID],
+            [
+                call('service-{}-returned-letters-summary'.format(SERVICE_ONE_ID))
+            ],
+            None,
+            [
+                call('service/{}/returned-letter-summary'.format(SERVICE_ONE_ID))
+            ],
+            [
+                call(
+                    'service-{}-returned-letters-summary'.format(SERVICE_ONE_ID),
+                    '{"data_from": "api"}',
+                    ex=604800,
+                )
+            ],
+            {'data_from': 'api'},
+        ),
     ]
 )
 def test_returns_value_from_cache(