Why Pre-Test Preparation Matters
The DVSA publishes annual MOT failure statistics. Consistently, the top failure reasons include lighting defects, tyre issues, and driver visibility — all things you can check at home in 20 minutes. Catching a £5 bulb failure before the test saves you the cost of a retest fee (£30–£55) and the inconvenience of a second visit.
Lights — the Number One Failure Cause
Check every exterior light works:
- Headlights — dipped and full beam
- Front and rear fog lights
- Brake lights (get help from a second person or reverse towards a reflective surface)
- Rear lights and side lights
- Indicators — front, rear, and side repeaters
- Hazard lights
- Reverse lights
- Number plate lights
Bulb replacements for most cars cost £3–£8 and take under 10 minutes with a YouTube guide for your specific model.
Tyres
Check all four tyres for:
- Tread depth — minimum 1.6mm across the central three-quarters. Use the 20p test or a gauge.
- Sidewall damage — bulges, cuts, or cracks are dangerous faults
- Correct inflation — check against the placard in the door jamb or your handbook
Windscreen and Visibility
- A chip or crack in the driver's line of sight (40mm zone) will fail
- A chip larger than 10mm anywhere in the wipers' swept area will fail
- Wiper blades should clear the screen cleanly without streaking — replace if they smear
- Make sure the washer jets work and the bottle is full
Warning Lights
Any warning light that stays on during the test is a potential fail. The engine management light is an automatic failure. Check that:
- All warning lights illuminate briefly at startup (self-test) then go out
- No warning lights remain on during normal operation
Horn
Press it. A non-functioning horn is an automatic Major failure.
Under the Bonnet
- Check oil level (top up if low — a dry sump won't cause a MOT failure directly, but running with very low oil risks engine damage)
- Coolant level
- Brake fluid (the tester checks this; low fluid can indicate a leak)
- No obvious fluid leaks on the driveway where the car is usually parked
When to Book a Pre-MOT Inspection
If your car is over 5 years old, has high mileage, or you've noticed any handling, noise, or warning light issues, a pre-MOT inspection (£30–£50 at most independents) is a smart investment. The mechanic will identify borderline items so you can decide whether to fix them before the test rather than face a failure.
Quick Pre-MOT Checklist
- All lights — headlights, brake lights, indicators, fogs, number plate
- Tyres — tread 1.6mm+, no damage, correct pressure
- Windscreen — no chips in critical zones
- Wipers — clearing effectively, washer fluid full
- Horn — works
- No warning lights on dashboard
- No fluid leaks
- Car drives and brakes normally