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What are car registration numbers?

Every car on the UK’s roads has a registration number. But why is it important and what does it mean? Our guide explains.

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By Cazoo editorial team

Every car has a registration number, a combination of letters and numbers shown on a ‘number plate’ attached to the front and back of the car. They’re a legal requirement for using a car on the UK’s roads and they also give you some useful information about the car.

Here, we explain everything you need to know about registration numbers.

Why does my car have a registration number?

A car’s registration number distinguishes it from every other car on the road. The combination of letters and digits is unique to an individual car and allows it to be identified for a variety of reasons. The information linked to your car’s registration number is essential when you want to tax, insure or sell it and it allows authorities to track a car that has been involved in a crime or traffic offence. On a practical level, it also means you can pick your car out in a car park filled with similar makes and models.

Does a registration number identify a car’s owner?

All registration numbers are issued by the Driving and Vehicle Licensing Agency (DVLA) when a car is new. The registration is tied to both the car and its ‘keeper’ (DVLA doesn’t use the word ‘owner’), be they an individual person or a company. When you buy a car, you must notify the DVLA of the transfer of ‘keepership’ from the seller to you, which is recorded against the car’s registration. You then become the car’s ‘registered keeper’. Insurance, MOTs, breakdown cover and servicing are also tied to the car’s registration.

What does a registration number mean?

A registration number is a unique combination of letters and digits. Several formats have been used over the years; the current one is two letters/two digits/three letters. Here’s an example:

AA21 YYY

The first two letters are an area code indicating the DVLA office where the car was first registered. Each office has several codes – ‘AA’ refers to Peterborough, for example.

The two digits are a date code telling you when the car was first registered. So ‘21’ tells you the car was registered between 1 March and 31 August 2021.

The final three letters are randomly generated and simply mark the car out from all the other registrations that start with ‘AA 21’.

This format was introduced in 2001. It was designed to give more combinations of letters and digits than previous formats allowed.

When do registration numbers change?

The current registration number format uses two digits as a date code to indicate when a car was first registered. The code changes every six months, on 1 March and 1 September. In 2020, the code changed to ‘20’ in March (matching the year) and ‘70’ in September (the year, plus 50). In 2021, the code is ‘21’ in March and ‘71’ in September. And so on for subsequent years.

The format started on 1 September 2001 with the code ‘51’, and will end on 31 August 2050 with the code ‘50’. After that date, a new – as yet unannounced – format will be introduced.

There’s often a lot of excitement around ‘reg change day’. Many car buyers really value having a car with the latest date code. Around the same time, some dealers offer great deals on cars with the previous code, so you could pick up a bargain.

Do I need a number plate on my car all the time?

The law requires most vehicles on UK roads, including cars, to have a number plate showing the correct registration number attached to the front and back. There are a few vehicles, like tractors, that need only one plate on the back, and vehicles that don’t have to be registered with the DVLA, like bicycles, don’t need any number plates.

There are strict rules governing a number plate’s size, colour, reflectiveness and the spacing between the characters. Confusingly, the rules differ slightly depending on the registration format. 

There are other rules, too. You mustn’t block the view of the plate, for instance with a bike rack or trailer. You mustn’t use stickers or tape to alter the appearance of the plate. It must be kept clean and undamaged. The rear number plate lights must be working.

If your plate doesn’t meet the rules, your car could fail its MOT. The police can fine you and even confiscate your car. If you need to replace a damaged plate, they’re available from most car parts shops.

What are private registrations?

If you want something more distinctive or meaningful than your car’s original registration, you can buy a ‘private’ registration. There are thousands available from the DVLA, specialist auctions and dealers. If you can’t find one you like, the DVLA may be able to issue a registration just for you, so long as the combination of letters and digits meets some format requirements and doesn’t spell out anything rude. It can't make your car appear newer than it is, either. Costs vary from about £30 to hundreds of thousands for the most desirable registrations.

Once you’ve bought a private registration, you need to ask the DVLA to transfer it to your car. If you sell the car, you need to tell the DVLA so it can reinstate its original registration, and to have your registration transferred to your new car. 

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