Vehicles don't need an MOT until they are three years old. The exceptions are passenger vehicles such as taxis and ambulances, which need one after just one year.
Cars and motorcycles that are more than 40 years old are also exempt. This is because they are rarely driven, usually kept in good condition as 'classic cars', and because they are so different from modern vehicles that many MOT checks are irrelevant.
Other exemptions include tractors, goods vehicles powered by electricity, and trams.