The interactive website that partners The Car and Motorcycle Theory Test book
 

What if the vehicle is leased?

Only the vehicle’s registered keeper can apply to transfer or retain a registration number. The leasing company (if they are the keeper) would have the right to transfer or retain the registration number. If you still want to assign a registration number on a leased vehicle, check with the leasing company that they agree to you doing so and that they are prepared to co-operate with transferring or retaining the registration number in the future.