If you move, you must change your "carte grise" (within 1 month) because your address is written on it. It's compulsory.
Do I have to change the « plaques d'immatriculation » ?
Not necessarily. It depends if you bought your car in a different department. If so, then you'll have to change your
« plaques d'immatriculation » as soon as you receive the « carte grise », otherwise, you might keep them.
From April the 15th 2009 (concerning a new car) and from June the 15th concerning a second-hand car, and for any change (address or owner) the car will keep the same “plaques d’immatriculation” and “carte grise”.
Back to "carte grise"