Sharing a Planner Plan 1 plan with a guest user

Hey mate, 
Planner does support guest users, but it’s not smooth. Microsoft’s docs say guests can be added through Microsoft 365 Groups and they can do things like create tasks, edit details, and add files if group settings allow it. But they don’t have the same rights as full tenant members, so it often feels broken.

The error you’re seeing usually happens when group guest access isn’t set up properly in the tenant, or because of the way Teams and Planner link up. Even if the guest has a Planner Plan 1 license, that alone doesn’t fix it, the license doesn’t override group settings.

Guests also miss out on things like task assignment emails, and they can’t manage some plan settings. Basically, it works in theory, but in practice it’s hit and miss.

Common fixes are:

1. make sure Microsoft 365 Group guest access is enabled
2. or just give them a proper user account in your tenant