Since the start of the twenty first century, UK rules for the display and appearance of car registration plates have been altered by the national licensing agency, the Driver and Vehicle Licensing Agency (DVLA). The rules came into effect from 1 September 2001.

UK car number plates, from 1 September 2001, have to display the combination of letters and numbers making up the unique registration number in a sans serif font. This was introduced in order to enhance the reading capabilities of automatic number plate recognition systems (ANPR), as well as with the human eye.

The size of the letters and numbers is regulated to be between 50 and 79 millimetres high, with the width set at 14 millimetres. A space in between letters / numbers is 11 millimetres, and the space between a grouped set of letters / numbers is 33 millimetres. Legally allowed car number plates decorations or accessories include national symbols such as flags or national denotation symbols such as GB for Great Britain, SCO for Scotland and so on.

UK car number plates are required to be white at the front of the vehicle, and yellow at the back. On the car number plate itself, other than the series of unique letters / numbers and unobtrusive national symbols, nothing else is allowed. For antique or other vintage cars, some exceptions to the rules are made. Black plates, which used to be in circulation, are still allowed on older cars, providing they are legible.