Are 3D and 4D number plates legal in the UK?

Plates fitted from 1 September 2021 must meet BS AU 145e, which requires characters in a single shade of solid black with no two-tone, shadowed or 3D effect. Raised legal 4D plates that meet the standard do exist, so buy only from a supplier who will state the British Standard on the invoice. Earlier BS AU 145d plates remain acceptable on cars that already have them.

Will a dirty number plate fail an MOT?

Usually not, because a merely grubby plate is cleaned at the test rather than failed. A plate that is permanently faded, cracked or has a lifting reflective layer is a failure, as is one that is missing, insecure enough that it is likely to fall off, or made up with the wrong font, size or spacing.

Can I space out the letters on my number plate?

No. Misspaced or restyled characters do not conform to the requirements, so the plate is a major defect at the test, and this is the situation in which the DVLA is most likely to withdraw a personalised registration. Italic fonts, tinted backgrounds and shortened plates fall into the same category, however smart they look.

What do I need to buy a replacement number plate?

A registered supplier will make one up on production of your V5C, or a certified copy, together with photographic identification, and that is a legal requirement rather than a formality. A pressed or acrylic plate is £15 to £30 each, a pair typically £25 to £50, and the supplier's name and postcode must appear on the plate.

MOT defect file

Registration plate missing, insecure or illegible

Last updated 27 July 2026

Quick answer

A number plate is missing, hanging loose, or no longer readable — faded, cracked, dirty, obscured or made up with the wrong font or spacing. It fails the test and is a separate offence on the road.

Typical cost: £20–£60 per plate
DIY viability: Straightforward

For vehicles first registered from September 2001, characters are 79 mm high, normally 50 mm wide and formed with 14 mm strokes. Character gap and margin are 11 mm; the group gap is 33 mm. The figure 1 and letter I are narrower exceptions.

What you might notice

A plate hanging by one fixing, rattling at idle, or visibly lifting away from the panel
Characters that have faded to grey, or a yellow rear plate turned pale and chalky
Cracking, crazing or a lifting reflective layer, most often on a rear plate that has spent years facing the weather
Spacing, italic characters or a stylised font that looks smart and does not match the legal layout

What causes it

Adhesive pads or plastic fixings that have failed with age, leaving the plate held on by one screw
Ultraviolet fading, which affects the pigment in cheaper plates within a few years
Water getting behind the reflective film after a stone chip, so the layers lift and bubble
A novelty or show plate fitted deliberately — misspaced, italicised, tinted or 4D-lettered in a way the rules do not allow

Advisory or failure?

A registration plate that is missing, or so insecure that it is likely to fall off, is a major defect. So is one where the characters are missing, illegible, or do not conform to the requirements — wrong size, wrong spacing, the wrong font, or a background that is not white at the front and yellow at the rear. There is no dangerous grading for a plate, and a plate that is merely grubby is generally cleaned rather than failed, but a permanently faded or cracked one is a failure. Plates fitted from 1 September 2021 must meet BS AU 145e, which means a single shade of solid black with no two-tone, shadowed or 3D-effect characters; earlier plates to BS AU 145d remain acceptable on cars that already have them. Note that the plate lamp is assessed separately in the lighting section, so a plate can pass while its lamp fails, and vice versa.

Can you fix it yourself?

Straightforward

Buying and fitting a plate is genuinely simple. A registered supplier will make one up on production of your V5C or a certified copy and photographic identification, which is a legal requirement rather than a formality, and they will supply it to the correct standard by default. Fitting is two screws with coloured caps or a set of adhesive pads on a clean, dry panel. The traps are all in the specification: order it to BS AU 145e, keep the standard spacing whatever a show-plate site offers you, and use the correct character height rather than a shortened plate that happens to fit an aftermarket bumper. Fit the supplier's name and postcode as marked — it must appear on the plate.

What it costs

A pressed or acrylic replacement plate from a registered supplier is £15 to £30 each, with a pair typically £25 to £50, and a fitting kit a couple of pounds. Fitted at a garage or a plate shop, expect £30 to £60 for the pair including labour. Pressed metal and legal 4D plates cost more, £35 to £60 each, and are only worth buying from a supplier who will state the British Standard on the invoice. Where the plate mounts to a bumper with broken captive fittings or a damaged plinth, the plinth itself is £20 to £60 and is what pushes an otherwise trivial job up the range.

What happens if you ignore it

An illegible plate carries a fine of up to £1,000, and DVLA can withdraw a personalised registration from the vehicle entirely if the plate is misrepresented or misspaced, which is a real loss on a mark somebody has paid for. Practically, an unreadable plate defeats automatic number plate recognition, so you can expect problems with car park charges, toll and clean air zone payments, and any insurance claim where the other party's camera is your best evidence. A plate that finally falls off is worse again, since driving without a plate is an offence in its own right.

Common questions

What is the fine for an illegible number plate?: Up to £1,000, and the DVLA can withdraw a personalised registration from the vehicle entirely where the plate is misrepresented or misspaced, which is a real loss on a mark somebody has paid for. An unreadable plate also defeats number plate recognition, so expect trouble with car park charges, tolls and clean air zone payments.
Are 3D and 4D number plates legal in the UK?: Plates fitted from 1 September 2021 must meet BS AU 145e, which requires characters in a single shade of solid black with no two-tone, shadowed or 3D effect. Raised legal 4D plates that meet the standard do exist, so buy only from a supplier who will state the British Standard on the invoice. Earlier BS AU 145d plates remain acceptable on cars that already have them.
Will a dirty number plate fail an MOT?: Usually not, because a merely grubby plate is cleaned at the test rather than failed. A plate that is permanently faded, cracked or has a lifting reflective layer is a failure, as is one that is missing, insecure enough that it is likely to fall off, or made up with the wrong font, size or spacing.
Can I space out the letters on my number plate?: No. Misspaced or restyled characters do not conform to the requirements, so the plate is a major defect at the test, and this is the situation in which the DVLA is most likely to withdraw a personalised registration. Italic fonts, tinted backgrounds and shortened plates fall into the same category, however smart they look.
What do I need to buy a replacement number plate?: A registered supplier will make one up on production of your V5C, or a certified copy, together with photographic identification, and that is a legal requirement rather than a formality. A pressed or acrylic plate is £15 to £30 each, a pair typically £25 to £50, and the supplier's name and postcode must appear on the plate.

Cars this happens to most

Of every model with at least 2,000 tests in the DVSA data, these record registration plate missing, insecure or illegible on the largest share of their MOTs. Across all of them the typical rate is 0.3% of tests.

BMW I81.7%
37 times in 2,142 tests
BMW X71.5%
40 times in 2,595 tests
Mercedes-Benz G-Class1.3%
45 times in 3,477 tests
Audi Q81.2%
63 times in 5,286 tests
Porsche Taycan1.0%
82 times in 7,988 tests
Audi S51.0%
22 times in 2,163 tests
Ford Mustang0.8%
98 times in 12,306 tests
Maserati Ghibli0.8%
26 times in 3,334 tests

A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.

Pass rates for every make and model

Warning lights behind this

This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.

This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.

Has this been recorded on your car?

Check the full MOT history for any UK registration.