A vehicle registration plate is a metal or plastic plate attached to a motor vehicle or trailer for official identification purposes. The registration identifier is a numeric or alphanumeric code that uniquely identifies the vehicle within the issuing region's database. In some countries, the identifier is unique within the entire country. In others, it is unique within each state or province. There is also variation on whether the identifier is associated with a vehicle or a person. Depending on the country or region of issue, it may also be referred to as a license plate, number plate, vehicle tag, license tag, or simply tag.

Legal requirements

Most governments require a registration plate to be attached to both the front and rear of a vehicle, although certain jurisdictions or vehicle types, such as motorcycles, only require one plate, which is usually attached to the rear. National databases relate this number to other information describing the vehicle, such as the make, model, color, year of manufacture, engine size, type of fuel used and mileage recorded during the vehicles annual (or bi-annual) road worthiness test, Vehicle identification (Chassis) Number and the name and address of the vehicle's registered owner or keeper.

In some jurisdictions, these registration plates will be permanently assigned to that particular vehicle for its lifetime. Some countries permit the re-registration of the vehicle with "personal" ("vanity" or "Cherished Mark") plates. When the vehicle is destroyed or exported to a different country it will require re-registering in the country of import. China requires the re-registration of any vehicle that crosses its borders from another country, such as overland holiday tourist visits, regardless of the amount of time it is due to remain there; this has to be arranged with prior approval.

In others, such as U.S. states, where they are known as license plates, they require periodic changing. For cost-saving purposes, however, the tendency for the past three decades has been to simply replace a small decal on the plate's surface, or to use a decal on the windshield to indicate the current expiration date of the registration. Additionally, some jurisdictions follow a "plate-to-owner" policy, meaning that when a vehicle is sold, the seller removes the current plate(s) from the vehicle. Buyers must either obtain new plates from their jurisdiction of residence or attach plates that they already hold from that jurisdiction, as well as formally registering their vehicles, under the buyer's name and the plate number, with the appropriate authorities. A person who sells a car and then purchases a new one can apply to have the old plates put onto this car. One who sells a car and does not buy a new one may, depending on the local laws involved, have to turn the old plates in or destroy them, or may simply be permitted to keep them. Other states keep the plate with the vehicle when ownership passes.