Note: information below covers highlights and is not intended to be official or legal advice.
NEWS: FAA has pushed back RID enforcement 6 months. See separate info...
All drones and model aircraft weighing more than .55 lbs (250 grams) flown after September 16, 2023 must be equipped with Remote Identification broadcast. Craft weighing less are exempted UNLESS flown under Part 107 (commercial). All craft flown under Part 107 must comply, with each craft having its own RID capability. This includes law enforcement and agencies.
Craft flown as recreational can use add-on RID modules, and more than one craft flown as rec can use the same module. Part 107 (commercial) pilots can fly recreational, but the craft must be entered into the FAA recreational database, and can not be used commercially. To change from 107 to rec or reverse, (APPARENTLY) the craft must first be deleted from its current database, then reentered into the other database.
Newly purchased craft should have RID builtin, and in flight continuously broadcast craft serial number, latitude, longitude, altitude, and time mark. Older craft with add-on RID modules broadcast the same plus the module serial number. Craft with add-on modules are limited to line of sight flights.
Talk in the trade revolves around conjecture about (1) possible extension of the September deadline, and (2) possible enforcement grace period. Do not count on either of these; go ahead and get in compliance ASAP.