MOT fail reasons: what fails, what advisories mean, what to do next
Roughly 28% of cars fail their first attempt at the MOT. Here is what fails them, what each defect category means legally, and how the retest works.
The most common MOT fail reasons
The DVSA publishes defect data for every test. For class 3 and 4 vehicles (cars and light vehicles) in the 2024 to 2025 year, just over 28% failed their initial test, and the defects found break down like this:
| Defect category | Share of all defects at initial test |
|---|---|
| Lamps, reflectors and electrical equipment | 25% |
| Suspension | 19% |
| Brakes | 16% |
| Tyres | 13% |
| Visibility (windscreen, wipers, washers, view of the road) | 8% |
| Body, chassis and structure | 6% |
| Noise, emissions and leaks | 6% |
Figures are DVSA-published percentages of all defects recorded at initial tests, 2024 to 2025, rounded. Two things stand out:
- The biggest category is the cheapest to prevent. A quarter of defects are lights and electrical items, and many are simple blown bulbs you could have replaced at home for a few pounds.
- Tyres dominate the dangerous defects. In the same DVSA data, tyres accounted for around 60% of dangerous defects recorded, which is what happens when tread is driven down past the legal limit. If your car is going to be declared undriveable at a test centre, a bald tyre is the most likely reason.
Dangerous, major, minor, advisory: what each category means
Since 2018, every defect found in an MOT is placed in one of four categories, and the category determines both the test result and what you can legally do next.
| Category | Test result | What it means for you |
|---|---|---|
| Dangerous | Fail | A direct and immediate risk to road safety or the environment. Do not drive the vehicle until it is repaired. Driving it risks a fine of up to £2,500, 3 penalty points and a possible ban. |
| Major | Fail | The defect may affect safety, other road users or the environment. Repair it as soon as possible. You can drive the car away only if the previous MOT is still valid and it remains roadworthy. |
| Minor | Pass | No significant effect on safety yet. It is recorded on the certificate and should be repaired promptly before it deteriorates. |
| Advisory | Pass | An item the tester noticed starting to wear, such as brake pads getting low or tyres approaching the limit. Monitor it and plan the repair. |
Advisories explained: ignore them at your own cost
Advisories cause more confusion than any other part of the certificate. The essentials:
- They are not a fail and there is no fine for driving with advisories on your certificate.
- They are a prediction. "Brake pads wearing thin" this year is a brakes failure, or an emergency, next year. Most advisories are simply early-stage versions of the failure categories in the table above.
- They are public. Every advisory sits on the vehicle's MOT history, which anyone can look up. Buyers and dealers read them; a string of ignored advisories drags down what your car is worth. You can read any car's full history, advisories included, with our free MOT history checker, which is well worth doing before you buy a used car.
- Roadworthiness still applies. If an advisory item deteriorates into something genuinely unsafe between tests, driving the car can still be an offence, because you must keep a vehicle roadworthy at all times, not just on test day.
What to do after a fail
- Read the failure notice carefully. It lists each defect with its category. Separate the dangerous items (car stays put) from majors (repair promptly) and note any minors and advisories for later.
- Decide where to repair. The test centre may quote for the work, and having it done there keeps you inside the free-retest rules below. You are under no obligation, though; compare with other local workshops in our garage directory if the quote feels steep.
- Know your driving rights. If the previous MOT is still in date and no dangerous defect was recorded, you can drive the car, sensibly, to arrange repairs. If the old certificate has expired, you may only drive to or from repairs or to a pre-arranged retest. If anything is marked dangerous, the car does not move until it is fixed.
- Fix the cause, not just the ticket. A failed headlamp aim or a corroded brake pipe often has neighbours in the same condition. Ask the garage what is coming next; it is cheaper to plan than to be surprised at the next test.
Retest rules: what a second test costs
- Free retest: leave the vehicle at the test centre for repair and it is retested within 10 working days.
- Free partial retest: take it away and bring it back to the same centre before the end of the next working day, where the failure was on one of a set list of items such as lamps, tyres, mirrors, wipers, doors, the horn or number plates.
- Partial retest fee: take it away and return within 10 working days, and the centre can charge a partial retest fee.
- Full fee: miss those windows and you pay for a complete new test.
If you need a different centre for the retest, or you are booking a first test somewhere with better availability, browse MOT test centres across the UK by town.
Beat the statistics before the test
Look again at that failure table: lights, tyres, wipers and washers are all things you can inspect on your driveway, and together they account for a large slice of all defects. Ten minutes with the ignition on and a 20p coin for the tyre tread removes most of the easy ways to fail. Start by checking your MOT status and last test's advisories free: last year's advisories are the single best prediction of this year's fail.
Frequently asked questions
What are the most common MOT fail reasons?
DVSA data for cars and light vehicles in 2024 to 2025 shows lamps, reflectors and electrical equipment made up about 25% of all defects found at initial tests, followed by suspension at about 19%, brakes at about 16%, tyres at about 13% and visibility items such as wipers and windscreens at about 8%.
What is the difference between dangerous, major, minor and advisory MOT defects?
Dangerous and major defects both fail the vehicle. A dangerous defect means the vehicle must not be driven until repaired, and driving it risks a fine of up to £2,500, 3 penalty points and a ban. A major defect fails the test but the car can leave if the previous MOT is still valid. Minor defects and advisories do not fail the vehicle; they are recorded as items to fix or monitor.
Can I drive my car with MOT advisories?
Yes. Advisories do not fail the test and carry no direct penalty. But they flag wear that is likely to worsen, and they stay on the vehicle's public MOT history. Treat them as an early warning and a repair to-do list, not something to ignore.
What should I do if my car fails its MOT?
Get the failure items repaired, then use the retest rules: a retest is free if the vehicle stays at the test centre and is retested within 10 working days, and a partial retest before the end of the next working day is free for certain items. If a dangerous defect was recorded, the car must not be driven until it is fixed.