If you’re driving for a living, an MOT failure isn’t just an inconvenience — it’s a day (or more) of lost earnings while you sort it out. Most failures come down to a handful of predictable, checkable things. Here’s what to look at before you book.
1. Tyres
The legal minimum tread depth in the UK is 1.6mm across the central three-quarters of the tyre, all the way around. That’s the legal line — for a delivery vehicle covering high mileage, don’t wait until you’re at the limit. A £5 tread depth gauge (or the 20p coin test: insert a 20p into the main grooves — if you can see the outer band of the coin, you’re close to the limit) takes two minutes per tyre. Also check for sidewall bulges, cuts, and uneven wear, which usually points to a tracking or suspension issue worth getting looked at separately.
2. Lights
Every bulb — headlights (dip and main beam), sidelights, indicators, brake lights, fog light, number plate light — gets checked. Get someone to stand behind and beside the car while you cycle through each one, including hazards. A failed bulb is one of the most common (and cheapest to avoid) MOT fails.
3. Windscreen and wipers
Chips or cracks in the driver’s line of sight (roughly a 290mm-wide band in front of the steering wheel) are an MOT fail if they’re larger than 10mm, or larger than 40mm anywhere else on the swept area. If you’ve got a chip, get it repaired before the test — a repair is far cheaper than a replacement, and most insurers cover chip repairs with no excess. Also check your wipers actually clear the screen without smearing or juddering.
4. Brakes
You can’t easily inspect brake pad thickness yourself without taking a wheel off, but you can listen and feel: a high-pitched squeal under braking, or the car pulling to one side, are both signs worth getting checked before your test rather than during it.
5. Fluid levels and the basics
Engine oil, coolant, brake fluid, and screen wash should all be topped up to the correct level. These aren’t usually MOT fail points on their own, but a garage doing a pre-MOT check will flag them anyway, and it’s free to sort yourself first.
6. Number plates
Plates need to be the correct font, spacing, and clearly legible — no cracks, fading, or obscuring dirt. If you’ve had a plate replaced anywhere other than an official supplier, double check it meets the legal spec.
A pre-MOT checklist, in order
- Check all four tyres — tread depth and condition
- Test every light, including hazards and number plate light
- Check the windscreen for chips/cracks in the swept area
- Listen for brake noise, check for pulling
- Top up oil, coolant, brake fluid, screen wash
- Check both number plates are clean and undamaged
- Check horn works
- Check seatbelts click in and retract properly
Ten minutes with this list catches the majority of common, avoidable fails — the ones that cost you a re-test and a day off the road for something that would’ve taken two minutes to fix beforehand.
Grab the free MOT Prep Checklist to keep this list handy on your phone.