Since 1987, it has been law in the UK that all new cars are produced with rear seat belts; the law for all rear seat passengers aged 14 and over to wear seat belts was introduced in 1991.

Since 1998 it has also been law that every MOT check involves seat belt checks, and that should any seat belt be found not to comply with safety measures the car will automatically fail the MOT.

The seat belt check applies to the number of seats declared on the vehicle V5. i.e. if the V5 says five seats then to pass an MOT the tester needs to examine five seats and five seat belts.

To comply with the law, if you reduce or increase the seating capacity of the vehicle then you must also declare it to the DVLA and have the V5 updated accordingly.