UK number plates explained

A legal requirement in the UK, number plates are a way of identifying vehicles on the road. Have you ever wondered what the numbers and letters on a number plate actually mean? Or, are you unsure about the rules regarding private registration plates?

Whether you want to personalise a number plate or are interested to know what type of number plates are banned in the UK, then you’ve come to the right place. Here at Octane Finance, we answer these questions and more in our dedicated UK number plates article…   

How does the UK number plate system work?

The number plate system we use today was originally implemented back in 2001. As a general rule of thumb, number plates contain seven letters and numbers divided into two blocks of four and three. 

Although you may think number plates are a completely random selection of letters and numbers, there is in fact a set formula for a registration plate. The format is two letters, two numbers, one space, then three further letters:

1. The first two letters displayed are known as the DVLA (Driver and Vehicle Licensing Agency) memory tag
2. The following two numbers are the age identifier
3. The final three letters are in fact generated at random

You can understand more about how the system works by taking a look at our dedicated memory tag and age identifier number plate guides, below… 

What is the reg for 2023?

As of 1st March 2023, vehicle registration plates in the UK change to feature ‘23’ as the age identifier on all newly manufactured cars. Displayed after the initial two letters (the local memory tag), the number 23 will be replaced by ‘73’ on all new cars from 1st September 2023 as number plates get updated twice a year.

Why do number plates change twice a year?

The main reason that number plates are updated is to show where a vehicle was registered and how old it is. Registration plates for new vehicles change every six months, so that a car’s age can be recognised at a glance. 

With an ever-growing demand for new cars and vans, the updated age identifiers and mix of the random element letters also means that there are enough combinations of number plates to fulfil the constant supply needed.

Each year new registration plates are issued from 1st March until 31st August and 1st September until the end of February the following year. Read on to view the age identifier system…       

Memory tag system

As mentioned above, the memory tag system was implemented to identify the area where a vehicle was first registered. Also known as an area code indicator, each region in the UK is assigned its very own DVLA memory tag identifier as explained in the accompanying table:

Have you noticed there are letters missing from the memory tag identifier list? Great spot if so! The DVLA will not use the letters I, Q or Z in its local memory tag identifiers - Z will only ever be used as a random letter. 

Age identifier system

Since the number plate system was introduced in 2001, new vehicle registration plates are introduced twice a year on 1st March and 1st September, every year.

These twice-yearly launches determine the age identifier part of a number plate and follow a distinct formula. In March, a new number plate will display the last two digits of the year it was launched. In September, the numbers change to a different combination; in September 2001 this started with 51 and the number increases year on year until all the possible variations have been used. 

To help you understand more, take a look at the number plate guide, below. This table documents the age identifier number until the year 2049/2050 when the current system reaches 99 as the age identifier:  

What are the rules on UK number plates?

You may not realise, but there are certain rules when it comes to what a number plate must look like. To be classed as legal, the number plates displayed on your vehicle must:

• Be made from a material that is reflective
• The front plate must display black characters on a white background
• The rear plate must display black characters on a yellow background
• Not have a background pattern of any kind
• Display the company or dealership name of who supplied the number plate
• Display a British Standard number (this should read as ‘BS AU 145e’ for number plates fitted after 1st September 2021)
• Not have removable or reflective characters
• Be a single shade of black for characters on number plates fitted after 1st September 2021

For a slightly more bespoke look, your number plate can display the following:

• 3D (raised) black characters
• A green flash if you have a zero-emission vehicle
• A flag on the left-hand side from one of the four options:

1. Union Jack
2. Cross of St George
3. Cross of St Andrew
4. Red Dragon of Wales

• A national identifier from one of the following options:

1. UNITED KINGDOM, United Kingdom or UK
2. GREAT BRITAIN, Great Britain, or GB
3. CYMRU, Cymru, CYM or Cym
4. ENGLAND, England, ENG, Eng
5. SCOTLAND, Scotland, SCO or Sco
6. WALES or Wales

If you do choose to display a flag, then bear in mind it must be situated above the national identifier. Neither the flag or national identifier letters can appear on the number plate margin or be more than 50 millimetres wide. 

Number plate letter spacing, size and style

Did you know that each of the characters displayed on a UK number plate must be a certain height, width and size? The letters and numbers appearing on registration plates for vehicles purchased since 1st September 2001 will need to meet a certain set of standards:

- Characters must be 79mm tall
- Characters must be 50mm wide (except the number 1 or letter I)
- The thickness of the black print (character stroke) must be 14mm
- The space between characters must be 11mm
- The space between the age identifier and the random sequence of letters must be 33mm
- The margins at the top, button and sides of the number plate must be 11mm 

What letters are not allowed on number plates in the UK?

As a driver in the UK, you’ve probably noticed that not all letters are used on number plates. This is because some of them can be confused with other letters or numbers, meaning that a vehicle wouldn’t be able to be easily identified. 

The letters not used on UK number plates are the letter I as it looks like the number 1, or the letters O and Q as they can be confused with the number 0. Although there is one exception to this rule, as the letter O is used for Oxford in reference to the memory tag system. 

For the same reason, the letter U is not used because it can be confused with the letter V (already used in the memory tag system). The letter Z looks too similar to the number 2 on number plates, so this isn’t used either. There are slightly different rules for personalised number plates, which we’ve explained below.   

Illegal number plates in the UK

Year after the year, the DVLA issues a list of banned number plates in the UK. One of the main reasons they do so is because they may be deemed to cause offence or are in poor taste. 

As you can imagine, the option to personalise a number plate with distasteful three letter words at the end can prove all too tempting for some, which is why these measures are taken. We won’t go into detail with what some of these banned options spell - we’re sure you can work it out for yourselves!

But, it’s not just the random three letters at the end of a registration plate that can prove controversial. Every year many local memory tag and age identifier combinations are banned too, due to the fact that they may give the impression of a distasteful word. 

You may or may not be surprised that COVID-related words are an absolute no-go, examples include; CO22 RNA and CO22 ONA.   

Private number plates

If the standard number plate assigned to your vehicle isn’t for you, then you can of course opt for a personalised number plate instead. A private number plate can be purchased directly from the DVLA or a private dealer - if you’re opting to purchase a plate from a private dealer, then do make sure it is legally valid. 

We’d recommend buying a personalised number plate from the DVLA. Thanks to the dedicated DVLA Personalised Registrations online search tool, you can discover millions of personalised number plate options at the click of a button.

Happy shopping!