Most MOT failures aren’t caused by mysterious mechanical faults — they’re caused by small, visible, fixable problems that drivers could have spotted themselves. A quick once-over in the week before your test can be the difference between a pass and a fail, a retest fee, and a day without your car. Here are the ten checks that matter most, with exactly how to do each one.
The failures that catch drivers out most
Year after year, the same five categories dominate MOT failures: lights and signalling, suspension, brakes, tyres, and visibility (wipers, washers and the driver’s view of the road). Notice what’s on that list — almost everything is something you can inspect on your driveway in ten minutes. That’s the theme of this guide: the test rewards basic maintenance, not mechanical expertise.
1. Check all car lights
Faulty lights are one of the single most common reasons for failure, and also one of the easiest to fix. Walk around the car with a helper operating the controls, or use reflections in shop windows and garage doors if you’re on your own. Check headlights (dipped and main beam), sidelights, indicators (all four corners plus side repeaters), brake lights (including the high-level centre light), reversing lights, fog lights, and number plate lights.
What the tester looks for: every required lamp must work, show the correct colour, and — for headlights — aim correctly. Fail vs advisory: a blown bulb is a straight fail; badly aimed headlights fail too, though many test centres will adjust the aim on the spot.
2. Inspect tyres for wear and damage
Tyres must have at least 1.6mm of tread across the central three-quarters of the tyre, all the way round. The classic 20p coin test works: insert a 20p piece into the tread grooves — if the coin’s outer band is visible, the tread is below the legal limit. Also check sidewalls for cuts, bulges or cracking, and make sure all tyres are the correct size and load rating for the car. A mismatched space-saver fitted as a road wheel can cause problems too.
What the tester looks for: tread depth, structural damage, correct fitment. On cars fitted with a tyre pressure monitoring system, a malfunction warning light is a fail. Fail vs advisory: a cut deep enough to expose cords is a fail; minor perishing on an older tyre may be noted as an advisory instead.
3. Clean your number plates
An unreadable, cracked, dirty or incorrectly spaced number plate is an instant fail — and entirely avoidable. Wash both plates, check the characters match DVLA format (correct font, spacing and grouping), and make sure the plate lights illuminate them at night.
What the tester looks for: legibility, secure fixing, correct format, and illumination. Fail vs advisory: there’s little middle ground here — a plate the tester can’t read properly fails.
4. Windscreen, wipers and washers
Damage in the driver’s line of sight fails the test: chips or cracks over 10mm in the swept area directly in front of the driver are a fail, and damage over 40mm elsewhere in the swept area fails too. Run the wipers — they must clear the screen effectively without smearing or juddering — and check the washers actually spray. Top up the washer fluid; an empty reservoir that leaves the washers inoperative is a fail.
What the tester looks for: the driver’s view of the road must be unobstructed. Fail vs advisory: a small stone chip outside the swept area may be noted as an advisory; anything in the driver’s sight line is judged strictly.
5. Check brakes and handbrake
Listen for grinding or squealing, feel for pulling to one side or a spongy pedal, and test the handbrake on a gentle slope — it must hold the car stationary. The tester’s brake rollers measure braking effort and balance far more precisely than you can, so this check is about catching the obvious.
What the tester looks for: braking performance, balance across each axle, handbrake efficiency, and the condition of discs, pads, pipes and hoses. Fail vs advisory: pads worn close to the limit may earn an advisory; scored discs, leaking pipes or a handbrake that can’t hold the car are fails. A dashboard brake or ABS warning light indicating a fault is also a fail.
6. Keep the car reasonably clean
This one surprises people. The tester needs clear access to seatbelts, pedals, the driver’s seat adjustment and under-bonnet checks. A car so cluttered or filthy that the tester can’t work safely can have the test refused — and you may still be charged. Clear the footwells, make sure every seatbelt is reachable and unobstructed, and give the interior a basic tidy.
What the tester looks for: safe access to every testable item. Fail vs advisory: this is about the test going ahead at all rather than pass/fail — don’t give the tester a reason to turn the car away.
7. Top up fluids
Check screenwash (must spray — see tip 4), engine oil, coolant and brake fluid levels. Low fluids won’t always fail the test directly, but they signal poor maintenance, and some — like an empty washer bottle — will. More importantly, running the engine low on oil or coolant risks real damage that dwarfs the cost of a top-up.
What the tester looks for: fluid leaks (a serious brake fluid leak is a fail), and that washers and wipers function. Fail vs advisory: minor seepage may be advisory; an active leak that affects braking or leaves drips is a fail.
8. Sort dashboard warning lights
If a warning light is on, assume the tester will care. An illuminated engine management light fails the test because it affects the emissions assessment. ABS, airbag/SRS, brake system and electronic stability warning lights indicating faults are all fails. The rule of thumb: no warning lights showing a malfunction should be lit when you arrive.
What the tester looks for: warning lamps must illuminate with the ignition and then go out (or behave as the manufacturer intends). Fail vs advisory: a lit malfunction lamp is a fail — get any warning diagnosed and fixed before test day.
9. Seatbelts and horn
Pull every belt fully out: the webbing must not be frayed, cut or twisted, buckles must latch securely, and retractors must pull the belt back smoothly. Then press the horn — it must work and be loud enough to be heard. Both are quick checks with zero cost.
What the tester looks for: belt condition, anchorage security, buckle and retractor operation, horn function. Fail vs advisory: damaged webbing or a belt that won’t retract is a fail; slight fraying at the very edge may be advisory at the tester’s discretion.
10. Check your MOT history and due date
Before you book, run a free MOT history check on your registration number. Past advisories are a to-do list written by previous testers — if “brake pads wearing thin” appeared last year and you haven’t touched them, expect it to be a fail this year. Also confirm your due date: you can test up to a month (minus a day) early and keep the original expiry date, so there’s no reason to leave it to the last minute. Read our guide to the most common MOT failures to see what catches other drivers out.
Bonus tip — book early. Don’t wait until the expiry date. Booking a week or two ahead gives you time for a retest if needed and avoids the fine of up to £1,000 — plus invalid insurance — that comes with driving an untested car.
Consider a pre-MOT check
If you’d rather a professional did the once-over, many garages offer a pre-MOT inspection — typically under £30 — covering the same items above. It’s cheap insurance: catching a worn wiper blade or a blown number plate bulb beforehand costs pennies compared with a fail, a repair bill under time pressure, and a retest. Ask the garage to flag anything that would be an advisory too, so you can plan the work rather than firefight it.
Test-day checklist
- Enough fuel: the emissions test needs the engine at operating temperature — arrive with at least a quarter tank.
- Locking wheel nut key: if your wheels have locking nuts, leave the key in the car. Without it, the tester can’t remove the wheels and the test can’t be completed.
- Clear access: tidy the boot and footwells so the tester can reach everything.
- Booking confirmation: you don’t need to bring the V5C logbook, but having your booking reference to hand smooths check-in.
- Child seats: you can leave them fitted or remove them — just make sure the tester can still access the seatbelts.
Frequently asked questions
How long does an MOT take?
Usually 45 minutes to an hour. Most centres have a viewing area if you’d like to watch.
Can I drive my car if it fails?
Only in limited circumstances — for example, to a pre-booked repair or retest — and never if a fault is classed as dangerous. Our guide to what happens after an MOT failure explains retests, fees and your rights in full.
How much does a retest cost?
If the car stays at the test station and is retested within 10 working days, the partial retest is free. Take it away and return it to the same station within 10 working days and you’ll pay up to half the test fee; after 10 working days or at a different station, it’s a full fee again.
Should I fix advisories from last year’s test?
Yes — advisories are faults in waiting. A free MOT history check shows every advisory ever recorded against your car.
What should I learn first if I’m new to all this?
Start with our plain-English explainer: what an MOT test actually is.