If your drone was registered for ‘recreational’ use, removing the registration number is sufficient, because only your personal information is on file and until the registration expires (3 years), you can simply put the same registration number on a different drone and fly recreationally.

If your drone was registered for ‘commercial’ use, in addition to removing the registration number, you’ll want to log into the FAADroneZone and cancel the registration through the FAA’s online registration system.