The Deregulation (Motor Vehicles Tests) Order 1996
Section 47 of the Road Traffic Act 1988 makes it an offence for a vehicle to which the section applies to be used on a road unless a MoT test certificate has been issued for it within the previous twelve months. The section does not in general, apply to any vehicle until a specified period after it is first registered, the specified period being 3 years in some cases and one year in other cases. However, where a vehicle is tested within one month (two months in the case of a public service vehicle) before the expiration of a current certificate, the twelve month period is extended to twelve months from the expiration of that certificate.