Sumit,
You have to renew your
MOT before it expires because you are not allowed to drive a car without MOT unless you're taking the car to the garage for an MOT Test. You can however renew the MOT a couple of weeks before it expires and have the new expiry date future dated, that is, if your MOT expires on the 2nd of March 2008, you can have the new expiry date as 2nd March 2009 even if you've done the MOT test before 2nd of March 2008. Hope you're getting the idea!