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When MOT time rolls around, most drivers worry about brakes, emissions, or suspension issues. But one of the most common — and easily avoidable — reasons for MOT failure is the humble number plate. It might seem like a small detail, yet the MOT test has strict rules around plates, and even minor issues can lead to a fail.
The good news? Almost all number plate‑related MOT failures are quick, simple, and inexpensive to fix. In this guide, we’ll break down the 10 most common MOT number plate fails, explain why they matter, and show you how to sort them without spending a fortune.
1. Number Plates That Are Too Dirty to Read
It sounds obvious, but thousands of vehicles fail their MOT every year because the plates are simply too dirty. Mud, road salt, and grime can obscure characters, making them unreadable to both MOT testers and ANPR cameras.
How to Fix It Cheaply
A bucket of warm water and a sponge. That’s it. Clean your plates before the test — front and back — and you’ll avoid one of the easiest fails on the list.
2. Cracked or Damaged Plates
Even small cracks can distort characters or create sharp edges, which is enough for an MOT fail. Damage often comes from minor bumps, pressure washers, or stones flicked up from the road.
How to Fix It Cheaply
Replacement plates are inexpensive, especially when ordered online. RegPlates offers fully road‑legal replacements that meet all DVLA and MOT standards. You can explore options here:
3. Incorrect Spacing or Fonts
The MOT test follows strict DVLA rules on character spacing, margins, and font style. If your plate has been customised illegally — for example, squeezed spacing to mimic a name — it will fail.
How to Fix It Cheaply
Order a new, fully compliant plate. If you’re unsure whether your current spacing is legal, RegPlates has a helpful guide: https://www.regplates.com/number-plate-rules(regplates.com in Bing)
4. Faded or Discoloured Plates
Over time, UV exposure and weathering can cause plates to fade. Yellow rear plates often bleach to a pale cream, and white front plates can yellow or dull. If the contrast between the background and characters is reduced, it’s an MOT fail.
How to Fix It Cheaply
Replacement is the only option. Fortunately, modern acrylic plates are durable and affordable. If your plates are more than 5–7 years old, replacing them before the MOT is often a smart move.
5. Loose or Poorly Secured Plates
A number plate that’s hanging off, rattling, or insecure is a fail. MOT testers must ensure the plate is firmly attached and won’t fall off during normal driving.
How to Fix It Cheaply
A simple fix:
- Use new screws or sticky pads
- Ensure the plate is flush against the vehicle
- Avoid overtightening, which can cause cracks
A pack of adhesive pads costs just a few pounds and can be fitted in minutes.
6. Incorrect Colour or Reflectivity
UK law requires:
- White reflective plate with black characters at the front
- Yellow reflective plate with black characters at the rear
If your plates have tinted covers, coloured backgrounds, or non‑reflective materials, they will fail.
How to Fix It Cheaply
Remove any tinted covers immediately — they’re illegal. If the plate itself is non‑compliant, replace it with a standard reflective acrylic plate.
7. Missing Supplier Name or BS AU 145e Marking
Since September 2021, all new number plates must meet the BS AU 145e standard. This includes:
- The supplier’s name and postcode
- The British Standard code
- A valid font and layout
If these markings are missing, the plate is not road‑legal and will fail the MOT.
How to Fix It Cheaply
Order a new plate from a DVLA‑registered supplier. RegPlates ensures all plates meet the latest standards, so you’re covered.
8. Illegal Decorative Elements
This includes:
- Stickers
- Background patterns
- Non‑standard flags
- 3D gel characters that don’t meet the new standard
- Raised lettering that exceeds permitted dimensions
While some decorative styles used to be tolerated, MOT rules have tightened significantly.
How to Fix It Cheaply
Remove any stickers or covers. If the plate itself is non‑compliant, replace it with a legal version. You can still personalise your plate legally — just ensure it meets DVLA rules.
9. Incorrect or Missing Flags and Identifiers
Legal flags include:
- Union Jack
- Cross of St George
- Cross of St Andrew
- Red Dragon of Wales
- EU flag (for older plates only)
Anything else — such as football badges or novelty icons — is an MOT fail.
How to Fix It Cheaply
If your plate has an illegal flag, you’ll need a replacement. Legal flags are inexpensive and can be added when ordering a new plate.
10. Number Plates That Don’t Match DVLA Records
If the plate on the vehicle doesn’t match the DVLA registration, the MOT tester must fail the vehicle. This can happen if:
- A private plate was removed but the old plates weren’t refitted
- A plate was misprinted
- A cloned plate was unknowingly purchased
How to Fix It Cheaply
Check your V5C and ensure the plate on the car matches the official registration. If you’ve recently transferred a private plate, confirm the change on the official DVLA site:
If you suspect your plate may be cloned, contact the police and DVLA immediately.
How to Avoid MOT Number Plate Fails Altogether
A quick pre‑MOT check can save you time, money, and stress. Before your test:
- Clean both plates
- Check for cracks or fading
- Ensure the plate is secure
- Confirm spacing and font are legal
- Look for the BS AU 145e marking
- Remove any covers or decorations
If anything looks questionable, replacing the plate is usually the cheapest and easiest solution.
Why Number Plates Matter More Than You Think
Number plates aren’t just for identification — they’re essential for:
- ANPR enforcement
- Speed cameras
- Congestion and clean‑air zone charging
- Vehicle security
- Insurance validation
A non‑compliant plate can lead to:
- MOT failure
- Police fines
- Points on your licence
- Your vehicle being flagged as suspicious
Given how inexpensive legal plates are, it’s simply not worth the risk.
Final Thoughts
Number plate‑related MOT failures are some of the easiest to avoid — and the cheapest to fix. Whether your plates are dirty, damaged, faded, or non‑compliant, the solution is usually quick and affordable.
If you need new plates, want to check the legality of your current ones, or are considering a personalised registration, RegPlates has everything you need to stay road‑legal and stylish.
Jon Cherry is a Director of leading personalised number plate dealer Regplates.com. Jon has over 25 years industry experience handling some of the most expensive plates ever sold with many high profile and celebrity clients. Active since 1991 in the number plate industry, Jon is currently Chairman of the Cherished Numbers Guild, a trade body representing number plate dealers in the UK. Jon has written many articles on the industry and insight into the future of numberplates and the market as a whole.
