Should the vehicle fail, you will be issued with a VT3O Certificate stating the items causing the failure of the MOT test. Make sure that you are clear as to what rectification is required for a pass to be issued. In certain cases expert or special services may be required regarding emissions or welding.
There is no set time limit before a retest and it is at the discretion of the individual. Remember - a car that does not have as current MOT Certificate is not allowed to be used on the road except when going for repairs for an MOT test, or to a prearranged MOT test.