Most drivers give very little thought to their number plates once they are fitted. They go on the vehicle, they stay there, and unless something obvious happens like cracking or fading, they tend to be forgotten. The problem is that plates can drift outside the legal standard in ways that are not immediately obvious, and the consequences of driving with plates that fall short of the standard are real. This guide walks you through a straightforward self-assessment so you can check your plates with confidence and know exactly what to look for.
A plate that was road legal when it was fitted does not automatically remain road legal indefinitely. There are two reasons for this.
The first is physical deterioration. Plates are exposed to UV light, road spray, temperature changes, and cleaning products over their lifetime. A plate that was bright and crisp when new can become faded, yellowed, or cracked over time. Any of these conditions can take a plate outside the legal standard even if it was fully compliant when produced. Our article on faded number plates explains in detail how deterioration affects compliance and at what point a plate needs to be replaced.
The second reason is that the standard itself has been updated over time. Plates produced to an earlier version of British Standard may no longer meet BS AU 145e, which is the current specification. This is particularly relevant for vehicles that have not had their plates replaced for a number of years, and for used vehicles where the plate history is not known.
Working through these checks takes only a few minutes and covers the most common reasons plates are found to fall outside the legal standard.
Stand back from your vehicle and look at both plates in good daylight. You are looking for:
A plate that shows any of these issues should be replaced. A cracked plate will fail an MOT, and a faded plate may also fail depending on the degree of deterioration. Our guide to why number plates fail an MOT covers the inspection criteria in detail.
The reflective performance of a number plate is one of the requirements under BS AU 145e that cannot be assessed in daylight. Ask someone to stand behind your vehicle at night with a torch, or park facing a wall with your headlights on and observe the rear plate in your mirrors. A compliant plate should reflect light back brightly and clearly. A plate that looks dull or washed out under direct light at night has lost reflectivity and no longer meets the required standard.
Smoked or tinted overlays will also reduce reflective performance significantly. If your plates have any kind of tinted covering, they are not road legal regardless of the condition of the plate beneath.
Every character on a road legal plate must be in the Charles Wright 2001 font at the correct size: 79mm tall, 50mm wide (excluding the number 1 and letter I), with a stroke width of 14mm. Characters must be spaced 11mm apart, with a 33mm gap between the two character groups.
You do not need to measure these with a ruler in most cases. What you are looking for is any obvious deviation from the standard appearance: characters that look stretched, condensed, or italicised; a font that appears similar to the correct typeface but with different proportions or stroke weights; or spacing that is visually tighter or wider than expected.
If your plates were supplied by a registered plate maker and have not been modified, they should be correct. If you bought a vehicle and are unsure of the plate history, or if the plates look stylistically different to standard plates on comparable vehicles, it is worth investigating further.
Turn the plate over and look for the supplying company’s name or trading name, postcode, and British Standard reference. Every road legal plate produced by a registered supplier must carry this information on the reverse. If there are no supplier details on the back of your plate, it was not produced by a registered supplier and its compliance with BS AU 145e cannot be assumed.
This is one of the quickest checks you can do and one of the most revealing. A plate without supplier details is a strong indicator that it may fall short in other respects too.
The front plate must have a white reflective background. The rear plate must have a yellow reflective background. These are not optional and apply to all vehicles regardless of body colour or plate style. A white rear plate, a yellow front plate, or any background colour other than white at the front and yellow at the rear is not road legal.
This also applies to 4D plates and 3D gel plates. The raised character style does not change the background colour requirement. Our 4D legality guide covers how these requirements apply to raised character formats in detail.
Beyond the physical condition of the plates themselves, there are a few situations worth being aware of.
If you have recently purchased a used vehicle, the plates may have been on it for a significant period and their compliance history is unknown. Running through the checks above is a sensible step before your first MOT with the vehicle.
If you have a personalised or private registration, the characters must still meet the same font, size, and spacing requirements as any standard registration. A personalised plate is not exempt from BS AU 145e. If the plates displaying your personal registration were not produced by a registered supplier, they should be replaced.
If your vehicle has been modified in a way that affected the plate mounting position, it is worth checking that both plates are still correctly displayed and fully visible. A plate that is angled, partially obscured, or mounted in a position that makes it difficult to read at a normal distance may be flagged at a roadside check. Roadside plate checks are becoming more common, and the 2025 DVLA enforcement focus has increased the likelihood of plates being assessed outside of the MOT cycle.
If any part of your self-assessment raises a concern, replacing the plates is the straightforward solution. There is no benefit in waiting until an MOT forces the issue, and driving with a plate that is outside the legal standard carries a small but real risk each time the vehicle is on the road. The hidden consequences of an illegal plate are worth understanding before making that call.
Our full range of road legal plates includes standard 2D printed plates, 3D gel plates, square plates, specialist formats, and bike plates for motorcycles. All are produced to BS AU 145e and carry our supplier details on the reverse.
If you are not sure which format suits your vehicle, or if you have a specific question about whether your current plates are likely to be compliant, get in touch with us and we will give you a clear, honest answer. You can also browse our number plate accessories if you need fitting hardware alongside replacement plates.
Checking your plates takes only a few minutes. Getting it wrong, even inadvertently, is not worth the risk.
