Motorcycles and tricycles registered after 1.9.2001 must only display a number plate at the rear of the vehicle.
Motorcycles and tricycles registered before 1.9.2001 can display a number plate at the front but are not required to.

The characters may be smaller and follow the rules lined out below.

Character Height:	64mm
Character Width:	44mm
Character Stroke:	10mm
Space between characters:	10mm
Space between groups:	30mm
Top, side & bottom margin:	11mm
Space between vertical lines:	13mm

Motorcycles registered on or after 1 September 2001 must display a two-line number plate number plate.
Motorcycles registered prior to the 1 September 2001 may display a three-line plate, but one-line plates are illegal, irrespective of the date of registration of the motorcycle.