All vehicles that are driven on the road are required by law to have a valid MOT certificate, and this is separate to the Servicing on your vehicle.
The law states, that you must have an MOT test every year, unless your vehicle is under 3 years old, exceptions do apply for vehicles such as ambulances and taxi's where the requirement is every year regardless of age. All tests must be completed before the old one expires.
If your MOT has expired on your vehicle then you cannot drive it on the road unless you are driving it to a pre-booked MOT test.
If your vehicle passes its MOT test, then you will be issued an MOT certificate and your details will be updated on the national MOT database.
If your vehicle fails, then you will get a notification of failure and this will also be recorded in the national MOT database and you will be unable to drive your vehicle on the road unless it is to take it to a pre-booked appointment to have any areas of failure repaired, or to another pre-booked MOT test.