diff --git a/README.md b/README.md
index 3ce61ee..d838586 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,9 @@ Things that are not implemented:
 
 - Region settings
 - KMS settings
+- Custom ACK deadlines
+- ACK'd message retention
+- Authenticating PUSH delivery
 - The Schema API and any PubSub settings related to it
 - Authentication settings for Push subscriptions
 - Changing message retry backoff settings for a subscription may not fully take