US and Canadian license plates

A vehicle registration plate, also known as a number plate (British English) or a license plate (American English), is a metal or plastic plate attached to a motor vehicle or trailer for official identification purposes. All countries require registration plates for road vehicles such as cars, trucks, and motorcycles. Whether they are required for other vehicles, such as bicycles, boats, or tractors, may vary by jurisdiction. The registration identifier is a numeric or alphanumeric ID that uniquely identifies the vehicle owner within the issuing region's vehicle register. In some countries, the identifier is unique within the entire country, while in others it is unique within a state or province. Whether the identifier is associated with a vehicle or a person also varies by issuing agency.

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 motorboats, require only one plate, which is usually attached to the rear of the vehicle. National databases relate this number to other information describing the vehicle, such as the make, model, colour, year of manufacture, engine size, type of fuel used, mileage recorded (and other similar data in jurisdictions where vehicles are regularly inspected for roadworthiness every year or two), Vehicle Identification (Chassis) Number, and the name and address of the vehicle's registered owner or keeper.

In the vast majority of jurisdictions, the government holds a monopoly on the manufacturing of vehicle registration plates for that jurisdiction. Either a government agency or a private company with express contractual authorization from the government makes plates as needed, which are then mailed to, delivered to, or picked up by the vehicle owners. Thus, it is normally illegal for private citizens to make and affix their own plates, because such unauthorized private manufacturing is equivalent to forging an official document. Alternately, the government will merely assign plate numbers, and it is the vehicle owner's responsibility to find an approved private supplier to make a plate with that number.

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Wikipedia