MOT Test Guide: The Most Common Failures and How to Prepare Your Car

The annual MOT test is a legal requirement for all cars over three years old in the UK. Despite this, around 37% of vehicles fail first time — often for simple issues that could have been fixed cheaply in advance. Here's how to prepare.

The 5 Most Common MOT Failures

1. Lighting and Signalling (30% of failures)

The single biggest cause of MOT failure. This includes headlights, brake lights, indicators, fog lights, number plate lights, and even the dashboard warning lights.

DIY fix: Walk around your car and check every light. Have someone press the brake pedal while you check the rear. Replacement bulbs cost £2-£15 from Halfords and take minutes to fit on most cars.

2. Suspension (13% of failures)

Worn shock absorbers, damaged springs, worn ball joints, and deteriorated bushes are all common issues, especially on cars with higher mileage.

Signs to watch for: Excessive bouncing over bumps, clunking noises when turning, uneven tyre wear. Professional repair needed — expect £200-£600 per axle.

3. Brakes (10% of failures)

Worn pads, corroded discs, seized callipers, and low brake fluid all cause failures.

Signs to watch for: Squealing when braking, car pulling to one side, spongy brake pedal. Brake pad replacement: £80-£200 per axle. Discs and pads: £150-£400 per axle.

4. Tyres (8% of failures)

The legal minimum tread depth is 1.6mm across the central three-quarters of the tyre, around its entire circumference. Many experts recommend changing at 3mm for safety.

DIY check: Insert a 20p coin into the tread grooves. If you can see the outer band of the coin, the tread is too low. Also check for bulges, cracks, and cuts on the sidewall.

5. Driver's View of the Road (7% of failures)

Cracked or chipped windscreens in the driver's line of sight, damaged wipers that don't clear properly, and obstructed views all cause failures.

DIY fix: Replace wiper blades (£10-£25 per pair). Windscreen chips can often be repaired for free through your insurance — but must be done before the MOT.

Pre-MOT Checklist

• All lights working (headlights, brake lights, indicators, number plate light, fog lights)
• Tyre tread above 1.6mm, correct pressure, no damage
• Windscreen clean with no chips in the driver's zone (29cm swept area)
• Wiper blades in good condition
• Washer fluid topped up and jets working
• Horn working
• Mirrors intact and secure
• Seatbelts working and not frayed
• No excessive exhaust smoke
• Handbrake holding properly
• Number plates clean, legible, and correctly spaced

When to Book Your MOT

You can have your car tested up to one month before the expiry date without losing any days on your next certificate. Book early to give yourself time for any repairs before the deadline.

Want to check a vehicle's MOT history before buying? Use our MOT History Checker tool to view past test results, advisories, and mileage records.