It depends, and key details are still being defined. The law is in force, and Article 18 gives Sources one year from entry into force to adjust their status. But that entry-into-force milestone is not the National MRV data-submission deadline — the submission deadline under Article 6 has not yet been set, and is expected to be published, with sufficient lead time, in MOCCAE's forthcoming technical guidance.
MOCCAE is also expected to confirm who must submit — likely a limited list of direct submitters plus aggregators reporting on behalf of others — so don't assume every UAE entity must register and file. The course doesn't tie you to a date; it teaches you to start data readiness now — applicability, source register, activity data, evidence — and to track updates with a regulatory watchlist, so you're ready when the guidance lands.