What Fails an MOT? The Most Common Failure Reasons
Most Common MOT Failure Reasons
Based on official DVSA data from millions of tests, these are the items that cause the most MOT failures:
1. Lighting and Signalling
Faulty or blown bulbs are consistently the number one cause of MOT failures. A blown brake light or indicator will fail the test. Walk around your car and check every light before your appointment.
2. Suspension
Worn suspension components — ball joints, bushes, shock absorbers — are a major failure category. These often show up as knocking or uneven tyre wear before they become a test failure.
3. Brakes
Brake failures include worn pads and discs, seized callipers, leaking brake hoses, and poor braking performance on the roller brake tester. Brakes that pull to one side are also a fail.
4. Tyres
Tyres below the legal 1.6mm minimum tread depth, with cuts or bulges in the sidewall, or of the wrong type or size for the vehicle will cause a fail.
5. Driver's View of the Road
This covers windscreen damage (chips in the direct line of sight), dirty or damaged mirrors, wiper blades that don't clear effectively, and washer jets that don't work.
6. Fuel and Exhaust System
Exhaust leaks, missing or modified catalytic converters, removed DPFs (on diesels), and emissions that exceed the legal limits all cause failures.
7. Bodywork
Structural corrosion — especially on the chassis, sills, and floor — is a common fail on older vehicles. Sharp edges and damage that could injure pedestrians also fail.
8. Seat Belts
Frayed, damaged, or non-functioning seat belts fail the test. Inertia reel belts must lock properly.
9. Registration Plates
Non-standard fonts, incorrect spacing, damage that makes the plate unreadable, or plates that don't display both characters — these all fail.
10. Dashboard Warning Lights
An engine management light, ABS warning, or airbag light that remains on after startup is an automatic failure.
How to Avoid Failures
Most MOT failures are preventable with a simple pre-test check:
- Replace blown bulbs (buy a spare set — they're cheap)
- Check tyre tread with a 20p coin
- Test all seat belts
- Check windscreen for chips and cracks
- Listen for knocking from the suspension
- Check dashboard lights don't stay on after ignition
- Look for exhaust leaks or smoke
Failure Rates by Vehicle Type
Older vehicles fail at a higher rate. Statistics show that cars over 10 years old have a significantly higher failure rate than newer vehicles. The overall UK MOT pass rate is around 55–60% on first attempt.
After a Failure
If your vehicle fails, you'll receive a VT30 certificate listing the failure reasons. You can get it repaired and retested — if done at the same garage within 10 working days, the partial retest is usually free.