The small lamp that illuminates the rear number plate isn't lighting. If a plate has two lamps and one is out, it's still recorded. It's one of the most common and cheapest MOT failures there is — and one almost nobody notices, because you can't see it from the driver's seat.
Wording as it commonly appears on an MOT certificate: “Registration plate lamp not working”.
What does it mean?
The small lamp that illuminates the rear number plate isn't lighting. If a plate has two lamps and one is out, it's still recorded. It's one of the most common and cheapest MOT failures there is — and one almost nobody notices, because you can't see it from the driver's seat.
How serious is it?
Usually recorded as: Minor. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- A blown festoon or capless bulb
- Water in the lamp unit corroding the contacts, which is very common on hatchbacks and vans
- A cracked lens letting the weather in
- An aftermarket LED unit that has failed or was never wired correctly
What a mechanic would check
Sidelights on, then walk to the back of the car — that's the whole test. If the bulb is good I check the holder for green corrosion and the earth, because on a lot of cars it's the earth in the boot lid loom that has broken, not the bulb.
What might need replacing
- A bulb
- A plate lamp unit
- Cleaning up corroded contacts or repairing an earth
Can you still drive it?
Perfectly safe to drive, but it's a fixed-penalty offence in its own right and it fails the MOT every time. Check it whenever you check your other bulbs.
Repair cost
This is the cheapest fix on the whole certificate — usually a bulb and five minutes. Worth doing yourself before the test.
Before the retest
Walk round the car with someone working the switches: dipped, main, sidelights, indicators, hazards, brake lights including the high-level light, rear fog and number plate lamps. A new headlamp bulb or unit should be followed by a beam aim check, because a correctly working lamp aimed into oncoming traffic still fails. Wipe lenses clean and make sure no warning lights stay on after start-up.
Retest rules
If the vehicle stays at the test centre for repair and is retested within 10 working days, a partial retest is often free; some items qualify for a free retest if you bring the car back by the end of the next working day. The exact conditions are set out on GOV.UK, so confirm with the test centre before you leave. A major or dangerous failure means the car cannot legally be driven away unless the previous MOT is still valid and nothing dangerous was recorded — check your certificate first.
Related help
More lights failures · MOT failure decoder · Ask a mechanic about your certificate
This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.