What's checked in an MOT (and how to pass first time)
By James Snow
Owner and mechanic, SV Autos
Published July 2026, updated September 2026
An MOT is the annual test that checks a car still meets the minimum legal standards for safety and exhaust emissions on the day it is tested, and it is required by law once the car is three years old.
Most MOT fails aren't big, expensive faults. They're small things like a blown bulb or a worn wiper that could have been sorted in five minutes at home. If you know what the tester is actually looking at, you can check the obvious stuff yourself and give the car a proper chance of passing first time. Here's the full list, the usual culprits, and what to look over the night before.
One MOT failure in six was something small: 9,880 cars failed on nothing but bulbs, wipers, washers or a number plate.
What the tester actually checks
The MOT is a set safety and emissions check against the standards on the day of the test. The tester works through the whole car looking for anything worn, broken or not up to the legal minimum. It's a fixed list, so nothing is down to opinion.
These are the main areas they go through:
What do they check on the brakes?
Pad and disc condition, the handbrake, and then a measured test of how hard the car actually stops and whether it pulls to one side. The measured part is why brakes cannot be signed off on a driveway walk round.
What counts as a legal tyre?
At least 1.6mm of tread across the central three quarters and right round the tyre, no cuts or bulges, and the right size and type for the car. The test looks at the worst point, not an average, so one bald edge fails it.
Why do lights fail so many cars?
Because a single dead bulb is an instant fail and nobody notices their own brake lights. Aim matters too: a headlamp pointing too high dazzles oncoming drivers and fails even when the bulb is fine.
What does the emissions test involve?
The car is run up and the exhaust is sampled against the limits for its engine and age. Diesels are also checked for visible smoke. There is no way to check this at home, which is one of the things a pre-MOT check is for.
Can rust fail the car?
Yes, but only where it matters. Surface rust on a wing is cosmetic. Corrosion within 30cm of a suspension or brake mounting, or anywhere structural, is a fail, and so are sharp edges from rotten bodywork.
- Brakes: pads, discs, the handbrake, and a proper test of how well the car stops
- Tyres and wheels: tread depth, condition, and the right size and type fitted
- Steering and suspension: play, wear, and anything loose or damaged
- Lights and indicators: that they all work, aim correctly and are the right colour
- Wipers and washers: that they clear the screen properly
- Windscreen: chips or cracks in the driver's line of sight
- Seatbelts: condition and that they lock and hold
- Mirrors: that the required ones are there and not damaged
- Exhaust and emissions: that it's secure, not blowing, and within limits
- Horn, number plate and VIN: that they work and are correct and readable
- Body and structure: no sharp edges, serious corrosion or damage
Why the small stuff fails the most
The faults that fail the most cars are the ones you'd never think of as a problem. A single blown bulb is an instant fail, and so is a wiper blade that smears instead of clearing the screen, or a washer bottle that's run dry.
None of these are engine faults or big repairs. They're the kind of thing that goes unnoticed day to day, then costs you a re-test because nobody looked before the car went in.
- Lights and bulbs: a blown headlight, brake light or indicator
- Tyres: tread under the 1.6mm legal limit, or damage to the sidewall
- Brakes: worn pads or discs, or a weak handbrake
- Wipers and washers: worn blades or an empty screenwash bottle
- Number plate: cracked, faded or hard to read
Check these the night before
A quick walk round the car the evening before the test catches most of the common fails while there's still time to fix them. You don't need any tools, just five minutes and someone to help with the brake lights.
Turn everything on and walk round: headlights on full and dipped, indicators, hazards, and get someone to press the brake pedal while you check the rear lights. Top up the screenwash, give the wipers a test on a wet screen, and have a look at your tyres for tread and any bulges or splits. A quick wipe of the number plate finishes it off.
- Walk round with all the lights on and check every bulb
- Have someone press the brake pedal while you watch the brake lights
- Top up the screenwash and test the wipers on a wet screen
- Check tyre tread (a 20p coin edge is a rough guide) and look for damage
- Give the number plate and windscreen a clean
- Listen for the handbrake holding on a slope
What you can't check yourself
Some of the list needs the car up on a ramp or proper test gear, so there's a limit to what you can spot on the driveway. Brake performance, emissions, and worn steering or suspension joints all need looking at underneath or with the right equipment.
That's the gap a pre-MOT check fills. We go over the same areas the tester will, find anything likely to fail, and can put most of it right before the car ever goes in for the real thing.
Advisories are worth reading
An MOT pass can still come with advisories. These are things that are legal for now but heading towards a fail, like a tyre getting low or a brake pad wearing thin. They're the tester telling you what to keep an eye on.
It's worth reading them rather than filing the certificate away. Sorting an advisory early, in your own time, is nearly always cheaper and less stressful than leaving it until it fails next year.
What actually fails, in our own data
Every failure item we counted, ranked, from the DVSA anonymised MOT records for our area. The percentage is the share of failed cars carrying that item, so a car with three faults appears in three rows.
| Failure item | Failed cars | Share of failed cars |
|---|---|---|
| A tyre seriously damaged | 8,939 | 15% |
| The aim of a headlamp is not within limits laid down in the requirements | 7,683 | 12.9% |
| A lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning | 5,976 | 10% |
| A suspension pin, bush or joint excessively worn | 5,829 | 9.8% |
| Windscreen washers not working or not providing sufficient fluid to clear the windscreen | 4,875 | 8.2% |
| A spring or spring component fractured or seriously weakened | 4,842 | 8.1% |
| Wiper blade missing or obviously not clearing the windscreen | 4,467 | 7.5% |
| A suspension joint dust cover missing or no longer prevents the ingress of dirt etc | 3,681 | 6.2% |
| A tyre cords visible or damaged | 3,420 | 5.7% |
| Tyre tread depth not in accordance with the requirements | 3,341 | 5.6% |
Sample: 59,747 failed cars, from 210,390 tests. Source: SV Autos analysis of DVSA anonymised MOT data, computed 2026-09-23.
Look at what sits near the top. A damaged tyre, a headlamp pointing the wrong way, a dead bulb, a washer that will not clear the screen. Most of that is visible from your own driveway the night before, which is the entire argument for looking.
How the odds change as a car gets older
The same records, split by how old the car was on the day of the test. This one is a straight failure rate: the share of tests at that age that failed.
| Age at test | Tests | Failed | Failure rate |
|---|---|---|---|
| 2 to 3 years | 17,715 | 2,356 | 13.3% |
| 4 to 5 years | 22,650 | 3,399 | 15% |
| 6 to 7 years | 28,375 | 5,368 | 18.9% |
| 8 to 9 years | 32,362 | 7,879 | 24.3% |
| 10 to 11 years | 29,263 | 8,895 | 30.4% |
| 12 to 13 years | 22,522 | 8,136 | 36.1% |
| 14 to 15 years | 19,091 | 7,765 | 40.7% |
| 16 to 17 years | 13,733 | 5,927 | 43.2% |
| 18 to 19 years | 9,954 | 4,263 | 42.8% |
| 20 years or older | 14,504 | 5,739 | 39.6% |
Sample: 210,390 tests. Source: SV Autos analysis of DVSA anonymised MOT data, computed 2026-09-23.
A car at two to three years old fails about one time in eight. By sixteen it is closer to one in two. If yours is over ten, the night-before walk round stops being optional and a pre-MOT check starts paying for itself.
Last year's advisory against this year's fail
This is the one worth your time. We followed the same cars from one test to the next and compared those advised on a system against those not advised on it.
| System | Advised last year, failed this year | Not advised, failed this year |
|---|---|---|
| Steering | 17.02% (306 of 1,798) | 1.59% (1,942 of 122,332) |
| Lamps and electrics | 27.91% (965 of 3,458) | 11.27% (13,603 of 120,672) |
| Suspension | 17.21% (3,361 of 19,527) | 7.06% (7,384 of 104,603) |
| Brakes | 9.25% (2,438 of 26,358) | 3.91% (3,820 of 97,772) |
| Tyres | 11.7% (4,164 of 35,595) | 6.44% (5,699 of 88,535) |
Sample: 124,130 cars matched across two consecutive tests. Source: SV Autos analysis of DVSA anonymised MOT data, computed 2026-09-23.
An advisory is not a note for the file. On every system we measured, being advised one year made failing the next several times more likely, and steering is the starkest of them. If you were advised on something, that is the thing to sort.
How this compares nationally
DVSA publishes the national picture, and it is counted differently from ours. Their figure is the share of ALL tests that failed on a category. Our table above is the share of FAILED cars carrying that item, so the two sets of percentages are not comparable and should not be read side by side. On DVSA's measure, 26.75% of class 3 and 4 tests were initial failures in the first quarter of the 2026 to 2027 financial year, and lamps, reflectors and electrical equipment was the largest single category at 9.98% of tests.
Common mistakes
Timing
Booking the test for the day the current certificate runs out.
Book up to a month minus a day early. You keep the same renewal date, so there is nothing to lose and time to fix whatever comes up.
The night before
Assuming the lights are fine because you have not noticed one out.
Walk round with everything switched on and get someone to press the brake pedal. Nobody sees their own brake lights, and one dead bulb fails the car.
Tyres
Checking the tread in one spot and calling it done.
Check across the width and right round the tyre. Wear is rarely even, and the test is judged on the worst point rather than an average.
Advisories
Filing the certificate away without reading what the tester wrote on it.
Read them the day you get them. Our own figures say an advisory is the best warning you get about next year's fail.
What a pass means
Treating a pass as proof the car is mechanically healthy.
The MOT does not test the engine or gearbox at all. A car can pass on Monday and still be well overdue a service.
In this guide series
This page is the hub. These go deeper on one part of it each.
- MOT advisories explained
What an advisory actually means, which ones to deal with first, and why last year's is the best warning you get about this year.
- How to check when your MOT is due
The free GOV.UK check, what happens if it lapses, and why booking a month early costs you nothing.
- How to check a car's MOT and service history
Reading a car's full test record before you buy it, including the mileage trail and the advisory that keeps coming back.
Key Takeaways
- Walk round the car the night before and check every bulb, with someone pressing the brake pedal for you.
- Top up the screenwash and replace any wiper blade that smears, because both are instant fails.
- Accept that brakes, emissions and suspension joints need a ramp, so book a pre-MOT check for those.
- Read the advisories on the certificate instead of filing it away.
- Sort an advisory in your own time, before it turns into next year's fail.
Primary Sources and Further Reading
- DVSA, Anonymised MOT tests and results
The raw records behind every table on this page. Published openly, so our analysis can be repeated.
- DVSA, MOT inspection manual: cars and passenger vehicles
The actual rules a tester works to, section by section. The final word on what passes and what does not.
- DVSA, MOT testing data for Great Britain (table MOT03)
The national failure rates quarter by quarter, counted differently from ours as set out above. Download table MOT03 for class 3 and 4 vehicles.
- GOV.UK, Check the MOT history of a vehicle
Free, needs only the registration, and shows every advisory the car has ever been given.