The instructions to tax your car on the GOV.UK website is reproduced below:

To tax your car, motorcycle or other vehicle you will need to use a reference number from:

• a recent reminder (V11) or ‘last chance’ warning letter from DVLA
• your vehicle logbook (V5C) - it must be in your name
• the green ‘new keeper’ slip from a logbook if you have just bought it

If you do not have any of these documents, you will need to apply for a new logbook.

You must tax your vehicle even if you do not have to pay anything, for example if you are exempt because you are disabled. This last point is important as exempt vehicles now include electric vehicles. 

A late licensing penalty (LLP) letter is issued automatically. LLP is set at £80 reduced to £40 if paid within 33 days.

If the penalty is not paid, the case will be referred to a debt collection agency.

If you pay by Direct Debit and fail to make the payment, DVLA may stop you from using this payment method in the future.