How to delete reminders on MacOS Big Sur?

Hi margalina,

We appreciate you reaching out through Apple Support Communities for help deleting reminders on your Mac. We're glad to help!

So that we're on the same page, let us know the exact version of macOS Big Sur. This can be found under Apple menu () > About this Mac.

Is the Delete key working in all other apps as expected?

Have you had a chance to restart your Mac since noticing this behavior? If not, please do so now. Here's a guide to help:

Log out, sleep, wake, restart, or shut down your Mac - Apple Support

We're here for you if you've got any questions.

Have a great day!

Choose the specific Instance of the Reminder and Right Click - it should bring up another Menu and choose Delete.