Most Common MOT Failures in 2026: Top 10 Reasons Cars Fail

Every year, roughly two in five vehicles presented for an MOT in the UK are handed back with either a failure or an advisory notice. Understanding the most common MOT failures in 2026 can save you time, money, and the inconvenience of a re-test fee. The good news is that the vast majority of failure items can be identified with a careful pre-MOT inspection — no specialist tools required.

The Driver and Vehicle Standards Agency (DVSA) publishes annual data on MOT outcomes. Lighting, tyres, and brakes consistently sit at the top of the list, accounting for over half of all failures. Here we break down the top ten culprits and explain exactly what testers look for.

1. Lighting and Signalling

Faulty lights remain the single biggest reason for MOT failures year after year. Testers check every external lamp: headlights, brake lights, rear fog lights, reverse lights, indicators, and number-plate illumination. A blown bulb costs under £5 to replace yourself, yet it is still the most preventable failure category. Walk around your car at night before the test and ask someone to operate the controls while you check every lamp is working. Also verify that headlight aim is correct — badly aligned beams dazzle other drivers and will earn an immediate failure.

2. Tyres

Tyre-related defects are the second most frequent cause of failure. Testers examine tread depth across the central three-quarters of each tyre: the legal minimum is 1.6 mm across a continuous band around the full circumference. In practice, many safety experts recommend replacing tyres at 3 mm. Beyond depth, inspectors check for cuts, bulges, and uneven wear patterns that indicate suspension or alignment issues. Even a single cracked sidewall can result in a dangerous defect classification, meaning the car cannot legally be driven until it is repaired.

3. Brakes

Brake system defects account for a large share of the most common MOT failures in 2026. Testers use a rolling road brake-testing machine to measure the stopping force generated at each wheel. They also physically inspect disc and pad condition, brake lines for corrosion or leaks, and the handbrake efficiency. Worn discs showing deep scoring or lipping, seized callipers, and corroded brake pipes are common reasons for referral. If you notice a spongy pedal, pulling to one side, or a grinding noise during braking, have the brakes inspected before the test.

4. Driver Vision and Windscreen

The windscreen is divided into two zones. Zone A is a 290 mm wide central band directly in front of the driver; any damage larger than 10 mm in this area results in a failure. Zone B covers the remainder of the swept area, where damage larger than 40 mm is a failure. Chips that have been professionally repaired and are not in the driver's direct line of sight usually pass. Wiper blades are also checked: if they smear excessively or fail to clear the screen effectively, that is a failure too.

5. Exhaust Emissions

Emission testing has tightened considerably since the introduction of the Euro 6 standards. Petrol cars are assessed for carbon monoxide (CO) and hydrocarbons (HC) at idle, while diesel vehicles must pass an opacity (smoke density) test. A blocked diesel particulate filter (DPF) is a particularly common cause of failure and can be expensive to rectify. If your diesel has been driven predominantly on short urban journeys, the DPF may not have regenerated properly. A long motorway run before the test can sometimes clear a partially blocked filter, but a fully blocked unit will need professional attention.

6. Suspension and Steering

Worn suspension components — including ball joints, tie rod ends, shock absorbers, and anti-roll bar bushes — are a growing failure category as the UK car parc ages. Testers use a suspension testing rig and a visual inspection on a ramp to identify excessive play or corrosion. Steering rack gaiters that are split or missing will fail the car outright. If you notice clunking over bumps, excessive body roll, or vague steering, arrange a suspension check before your MOT date.

7. Bodywork and Structure

Sharp edges caused by corrosion or accident damage that could injure a pedestrian or cyclist will result in a failure. More seriously, structural corrosion in load-bearing areas — sill sections, floor pans, and chassis legs — can lead to a dangerous defect classification. Many older UK cars suffer from underbody rust, especially those that have spent years in areas where roads are heavily salted in winter.

8. Number Plates

It sounds minor, but number plate non-compliance is a surprisingly common failure. Plates must use the correct font (Charles Wright 2001), display the correct spacing, and be properly lit. Aftermarket "show plates" with stylised fonts, flags in the wrong position, or missing BS AU 145e certification will fail the test. Replacement plates cost very little and should be one of the first things checked.

9. Seat Belts

Every seat belt in the vehicle is checked for condition and operation. Frayed webbing, inertia reel mechanisms that do not lock, and buckles that fail to release cleanly all result in failures. Because seat belts are rarely tested in day-to-day use, owners often overlook deterioration. Pull each belt out fully and check for cuts or fraying before the test.

10. Fuel and Exhaust Systems

Fuel leaks are an immediate dangerous defect. Testers will also check that the exhaust system is securely mounted, free from excessive leaks, and not emitting fumes into the passenger compartment. Corroded exhaust hangers and failing catalytic converters are common issues on higher-mileage vehicles.

The best way to avoid a surprise failure is to carry out a pre-MOT check using our MOT checklist and to review your vehicle's test history for recurring advisory notices that may now have developed into failures. You can check your MOT history free of charge to see every past advisory, mileage reading, and failure item recorded against your registration.