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

What if you no longer want to assign the registration number?

If you are not going to assign the registration number, you can allow your right to end. You can then apply for a refund of the assignment fee you paid when you got the right. Your V750 or V778 will tell you how to do this.

If you allow your right to end, you will not be able to get it back at a later date.

You can only apply for a refund of the assignment fee after the right has run out and within six years of that date.