Every year, millions of UK cars fail their MOT. Of those failures, a huge chunk are for issues that cost less than £15 to put right — if you'd just checked them before the test.
This is the cheapest motoring lesson you'll ever learn: spend 30 minutes and £15 before your MOT, and you'll dramatically reduce your chances of paying for a retest, replacement parts, and the labour to fit them.
The Big Three Cheap Fails
According to DVSA data, the most common MOT failures in the UK are:
- Lights and signalling — bulbs out, lenses cracked, alignment off
- Suspension — usually more involved, but worth checking
- Brakes — pad wear, fluid level, performance
- Tyres — tread depth, sidewall damage
- "View of the road" — wipers, washers, mirrors
Of these, the first and fifth are the cheapest to fix yourself. Let's run through each.
1. Lights — The £3-£10 Fix
A single blown headlight bulb is enough to fail your MOT. So is a broken brake light, indicator, number plate light, or fog light.
Check every light on your car before the test:
- Headlights (both dipped and main beam)
- Front and rear indicators
- Brake lights (get someone to help)
- Reversing light
- Rear fog light
- Number plate lights (often forgotten)
- Interior dashboard warning lights
Replacement bulbs are inexpensive — typically £3-£10 a pair depending on type. H7 headlight bulbs and P21W brake light bulbs are the most common UK fits, but check your handbook for your exact car.
Most bulbs can be replaced without tools. There are step-by-step videos for almost every make and model online. The exceptions are some modern LED units, which often need professional replacement.
2. Wipers and Washers — The £15 Fix
We've covered wipers in detail elsewhere on the blog. The short version: replace your blades annually, and always check your washer fluid is topped up before the MOT.
A good set of Bosch Aerotwin wipers costs around £15-£25 for both fronts and will last 12+ months.
3. Number Plate — The £10 Fix
This catches a lot of people out. Your number plate must be:
- Securely fixed
- Clearly readable from 20 metres
- Compliant with the official font (Charles Wright)
- Not cracked, faded, or coloured incorrectly
If yours is faded, peeling, or has decorative additions, replace it. UK number plates from a registered supplier cost around £10-£25.
4. Tyres — The "Check Don't Pay" Fix
Tyres are the one item where you can't always cheap out, but you can avoid surprise failures:
- Check tread depth (legal minimum is 1.6mm across the central three-quarters)
- Inspect sidewalls for cuts, bulges, or cracks
- Check pressures (correct pressures help with brake balance and tyre wear)
A 20p coin is your friend — if you insert it into the tread groove and you can see the outer band, your tread is below 3mm. Below 1.6mm and it's an instant fail.
5. Boot, Bonnet and Door Catches
Often overlooked: if any of your catches don't open or close properly, that's an MOT fail. Lubricate them with a bit of WD-40 if they're stiff. Replacing a faulty door catch is more involved, but worth checking before the test.
Your Pre-MOT Toolkit
For about £30, you can equip yourself with everything you need to spot most MOT issues before the test:
- A set of replacement bulbs for your car
- A 5-litre bottle of screenwash concentrate
- A new pair of wiper blades
- A torch for checking lights yourself
- A tyre tread depth gauge (or a 20p coin)
The whole lot is available on eBay Motors UK's car parts shop — usually cheaper than Halfords and delivered to your door within a couple of days.
The Bottom Line
An MOT retest costs £54.85. A few replacement bulbs, a set of wipers, and 30 minutes of your time costs less than £30. The maths is straightforward.
And once your car's through the MOT — if it's time to upgrade — Car Cupid lets you search every major UK car site at once to find your next motor without the usual faff.