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

What if your right to assign or retain your registration number is due to end?

You must either assign the registration number or apply for an extension before this happens. Your V750 or V778 will tell you how to do this.

You will lose your right if you act too late.

You can extend the right to a registration number for either one year, two years or three years, paying the correct fee as shown on either the V750 or V778. These extension fees arenot refundable.