All new cars that are over three years old require a valid MOT certificate. This MOT needs to be renewed each year if you wish to drive the car on the road. The MOT can be carried out up to one month prior to the expiry date whilst still honouring the anniversary, so for example if you have your MOT done one month prior to it expiring then you will actually have 13 months until it is required to be done again.
The best time to get an MOT done ideally is at least a few weeks prior to the expiry. This then allows you plenty of time to either get repairs done or to decide if you want to get rid of the car / scrap it before you go ahead with any repair work. If you leave it until the day or so before the expiry date then you are often rushed in to having to get the work done without being able to shop around for the best price. If the car still has a valid MOT then you can still drive it even if it fails (up until the expiry date) as long as the reason it failed is not considered serious.