Anmeldung vs Abmeldung vs Ummeldung

Anmeldung is the first-time registration of a vehicle in your (or the keeper's) name — needed for new, imported or previously-deregistered cars. Ummeldung is a change of keeper or address — same car, new registration entry. Abmeldung (Außerbetriebsetzung) removes the car from active registration, stops insurance and tax, and lets you scrap, sell or export. Note: "Anmeldung" also colloquially means residence registration at the Bürgeramt — different process, same word.