Top 10 MOT Failure Reasons in 2025 & How to Avoid Them

Nearly 40% of UK vehicles fail their MOT test on the first attempt, with most failures being preventable through basic maintenance and pre-test checks. In 2024, almost 10 million MOT tests ended in failure, costing drivers time, money, and inconvenience.

This comprehensive guide reveals the top 10 reasons cars fail their MOT in 2025, based on official DVSA statistics. More importantly, you'll learn exactly how to check for these issues yourself and what it costs to fix them - helping you pass your MOT first time and avoid expensive surprises.

Official 2025 MOT Failure Statistics

According to the Driver and Vehicle Standards Agency (DVSA) data for Q3 2024-2025 (October to December), here's the state of MOT testing in the UK:

Key Statistics:

• 72% - National average pass rate
• 28% - Failure rate (approximately 10 million failures annually)
• 40% - Vehicles failing due to preventable issues
• 150+ - Safety and emission systems checked during each test

The data reveals that most failures happen because drivers skip simple checks and basic maintenance. Many issues that cause MOT failures can be identified and fixed for less than �50 if caught early.

#1: Lighting and Electrical Equipment (23.64% of All Defects)

Failure Rate: 10.60% of tests fail for lighting issues Defect Share: 23.64% of all defects found

Why It Fails

Lighting is the number one cause of MOT failures in the UK. The most common issues are:

• Blown bulbs - Headlights, brake lights, indicators, fog lights
• Cracked or damaged light lenses
• Poor headlight alignment - Dazzling oncoming traffic
• Corroded connections - Causing intermittent faults
• Number plate lights not working
• Indicator bulbs wrong colour (must be amber)

What's Tested

MOT testers check every external light on your vehicle:

• Headlights (dipped and main beam)
• Brake lights (including high-level brake light)
• Indicators (front, rear, side repeaters)
• Fog lights (if fitted)
• Reverse lights
• Number plate lights
• Hazard warning lights

How to Check Yourself

Walk-around test (takes 5 minutes):

1. Turn on dipped headlights - check both work
2. Switch to main beam - both should illuminate brighter
3. Turn indicators on - front, side, and rear should flash
4. Ask someone to press brake pedal - all brake lights illuminate
5. Turn on fog lights (if fitted) - should illuminate
6. Put car in reverse - reversing lights come on
7. Check number plate light - should illuminate plate clearly

Signs of potential failures:

• Dim lights (may indicate failing bulb)
• Flickering (loose connection)
• Cracked lens (water ingress causes failures)
• Condensation inside light units

Quick Fixes

Bulb replacement: �5-�15 per bulb

• Most bulbs can be replaced at home in 5-10 minutes
• YouTube has guides for specific car models
• Keep spare bulbs in your car

Lens cleaning/repair: �0-�30

• Clean lenses with warm water and car shampoo
• Remove condensation by leaving in sunshine
• Replace cracked lenses (�20-�80 depending on model)

Professional Repair Costs

If you need a garage to fix lighting issues:

• Bulb replacement: �20-�40 (including labour)
• Headlight alignment: �30-�50
• Wiring repair: �50-�150
• Complete light unit replacement: �80-�300

Pro tip: Check all lights 2 weeks before your MOT and replace any blown bulbs. It's the cheapest and easiest way to avoid a failure.

#2: Brakes (21.25% of Defects)

Failure Rate: 9.03% of tests fail for brake issues Defect Share: 21.25% of defects

Why It Fails

Brakes are the second most common failure category. Issues include:

• Worn brake pads - Below minimum thickness
• Worn or scored brake discs - Excessive wear or damage
• Low brake fluid - Below minimum level
• Brake imbalance - One side braking harder than the other
• Handbrake inefficiency - Won't hold car on slope
• Leaking brake components - Fluid leaks from calip

ers or lines

• Corroded brake pipes - Especially on older vehicles
• ABS warning light on - Indicates system fault

What's Tested

MOT testers use a roller brake tester to check:

• Brake efficiency - Must achieve minimum % (typically 50%+ for main brakes, 25%+ for parking brake)
• Brake balance - Left and right must be within tolerance
• Brake fluid level - Must be above minimum
• Brake pipes and hoses - No corrosion, damage, or leaks
• Brake pedal - Firm feel, no sponginess
• Handbrake - Holds car securely
• ABS - Warning light must go off after ignition

How to Check Yourself

Simple home checks:

1. Brake pedal feel - Should be firm, not spongy
2. Brake fluid level - Check reservoir under bonnet (between min/max lines)
3. Brake pad thickness - Look through wheel spokes (should see at least 3mm)
4. Handbrake test - Park on hill, handbrake should hold car without rolling
5. Listen for noises - Squealing or grinding indicates worn pads
6. Check for pulling - Car shouldn't pull to one side when braking

Warning signs:

• Squealing noise when braking (pads worn)
• Grinding noise (pads completely worn - metal on metal)
• Car pulls to one side (imbalance or seized caliper)
• Pedal feels soft or spongy (air in system or leak)
• Longer stopping distances (pads worn or fluid contaminated)

Quick Fixes

Brake fluid top-up: �5-�10

• Buy correct fluid type (usually DOT 4)
• Top up to max line
• Warning: Low fluid often indicates worn pads, not just needing top-up

Professional Repair Costs

• Front brake pads: �60-�150 (pair, fitted)
• Rear brake pads: �50-�120 (pair, fitted)
• Front brake discs + pads: �200-�400
• Rear brake discs + pads: �150-�300
• Brake fluid change: �40-�80
• Handbrake adjustment: �30-�60
• Brake pipe replacement: �80-�200 per section

Important: Worn brakes are safety-critical. If you suspect an issue, get it checked immediately. Don't wait for MOT.

#3: Suspension (10% of Failures)

Why It Fails:

• Worn shock absorbers - Excessive bouncing
• Broken springs - Cracked or snapped coils
• Worn bushes - Excessive play in suspension components
• Damaged anti-roll bar - Cracks or loose mounting

What's Tested

Testers check:

• Shock absorber condition (bounce test)
• Spring condition (no cracks or breaks)
• All bushes and mounting points
• No excessive play in components

How to Check

Bounce test:

1. Push down firmly on each corner of car
2. Release quickly
3. Car should bounce once or twice and settle
4. If it bounces 3+ times, shocks are worn

Listen for noises:

• Clunking over bumps = worn bushes or mounts
• Creaking = damaged springs
• Rattling = loose components

Costs to Fix

• Shock absorber pair: �150-�400 (fitted)
• Front springs: �150-�300 (pair, fitted)
• Rear springs: �120-�250 (pair, fitted)
• Suspension bushes: �80-�200 per set

#4: Tyres (Major Failure Category)

Why It Fails:

• Tread depth below 1.6mm (legal minimum across central 3/4 of tyre)
• Uneven wear - Indicates tracking or suspension problems
• Cuts or bulges in sidewall - Structural damage
• Cords visible - Tyre worn through to structure
• Wrong tyre size - Doesn't match V5C specification
• Perished rubber - Cracks in sidewall (age-related)

The 20p Test

Quick tread depth check:

1. Insert 20p coin into tread groove
2. If outer band of coin is visible, tread is below 1.6mm = FAIL
3. If outer band is hidden, you have legal tread depth

However: Consider replacing tyres at 3mm for safety, especially in wet weather.

Tyre Safety Checks

Before your MOT:

• Check all four tyres for tread depth (including spare if carried)
• Look for cuts, bulges, or punctures
• Check tyre pressure (correct pressure on sticker inside driver's door)
• Ensure valve caps are fitted
• Check tyres are correct size for vehicle

Costs to Replace

Tyre prices vary by size:

• Small cars (14"-15"): �50-�100 per tyre
• Medium cars (16"-17"): �70-�130 per tyre
• Large cars/SUVs (18"+): �100-�200 per tyre
• Fitting fee: Usually �10-�20 per tyre (balancing included)

Budget tyres vs premium: Budget tyres (�40-�60) meet legal standards but wear faster. Premium tyres (�80-�150) last longer and perform better in wet conditions.

#5: Windscreen, Wipers and Washers

Why It Fails:

• Windscreen chips or cracks - 10mm+ damage in "Zone A" (driver's direct view), or 40mm+ anywhere
• Worn wiper blades - Leaving streaks or unwiped areas
• Washer not working - Empty reservoir or faulty pump
• Damaged windscreen - Severe cracks affecting structure

Zone A Explained

Zone A is the area directly in front of the driver, swept by the wipers. Any damage here over 10mm = instant fail.

Outside Zone A: Damage up to 40mm in diameter is allowed (but still dangerous long-term).

DIY Checks

Windscreen:

• Look for chips or cracks
• Chips can be repaired if caught early (�30-�50)
• Cracks usually mean replacement (�150-�300)

Wipers:

• Test on all speeds
• Look for juddering or streaking
• Check blades for splits or tears
• Replace annually (�10-�30 per pair)

Washers:

• Top up washer fluid (�2-�5)
• Test spray reaches windscreen
• Check no leaks from bottle

Repair Costs

• Wiper blades: �10-�30 (pair)
• Washer fluid: �2-�5 (bottle)
• Windscreen chip repair: �30-�60 (often covered by insurance)
• Windscreen replacement: �150-�400 (insurance usually covers with excess)

#6: Emissions and Exhaust

Why It Fails:

• Excessive smoke - Diesel vehicles (blue, black, or white smoke)
• Emissions too high - Petrol or diesel exceeds limits
• Faulty catalytic converter - Not reducing emissions properly
• Exhaust leaks - Holes or loose connections
• DPF (Diesel Particulate Filter) issues - Warning light on or blocked filter

Emission Limits (2025)

Petrol cars (Lambda test):

• CO (carbon monoxide) must be below 0.2%
• HC (hydrocarbons) must be below 200ppm
• Lambda value must be 0.97-1.03

Diesel cars (Smoke test):

• Smoke density below specific limits
• DPF must be present and functioning (if fitted as standard)

Common Causes

High emissions:

• Poor engine tune
• Faulty lambda sensor
• Worn spark plugs
• Dirty air filter
• Failing catalytic converter

Diesel smoke:

• Blocked DPF
• Worn injectors
• Turbo problems
• Carbon build-up

DIY Prevention

"Italian Tune-Up" - Works surprisingly well:

1. Drive car at 3,000+ RPM for 15-20 minutes before MOT
2. Uses high revs to burn off carbon deposits
3. Clears DPF if partially blocked
4. Best done on motorway or dual carriageway

Other tips:

• Use quality fuel (super unleaded helps)
• Replace air filter regularly (�10-�30)
• Service engine on schedule
• Don't just do short journeys (carbon builds up)

Repair Costs

• Engine service: �150-�300
• Lambda sensor: �50-�150 (+ fitting �50-�80)
• DPF cleaning: �100-�200
• DPF replacement: �500-�2,000
• Catalytic converter: �300-�1,500
• Exhaust section replacement: �80-�300

#7: Steering

Why It Fails:

• Excessive steering play - Too much movement before wheels turn
• Worn track rod ends - Clunking when turning
• Loose or damaged steering rack - Play or leaks
• Power steering failure - Heavy steering or leaks
• Worn steering column joints

Home Checks

Steering play test:

1. Wheels straight ahead
2. Engine running (for power steering)
3. Turn steering wheel gently left/right
4. Should be minimal movement before wheels turn
5. Excessive play (more than ~25mm at wheel rim) = potential fail

Listen for noises:

• Clunking when turning = worn track rod ends
• Whining when turning = power steering pump issue
• Creaking = worn bushes

Costs

• Track rod ends: �80-�150 (pair, fitted + alignment)
• Power steering fluid top-up: �10-�20
• Power steering pump: �200-�400 (fitted)
• Steering rack: �300-�800 (fitted)

#8: Body, Structure and Corrosion

Why It Fails:

• Rust near seatbelt mounting points - Structural safety issue
• Corroded chassis or subframe - Excessive corrosion
• Sharp edges - Dangerous projections from bodywork
• Insecure body panels - Bonnet, doors, boot not secured properly

Critical Areas

MOT testers especially check:

• Seatbelt mounting areas - Any rust here = serious fail
• Chassis rails - Load-bearing structure
• Suspension mounting points - Corrosion weakens mounts
• Sills - Often rust from inside out

Prevention

Rust protection:

• Wash car regularly (especially underneath in winter)
• Treat minor rust early with converter and paint
• Wax sills and arches annually
• Check for water traps (blocked drain holes)

Costs

• Minor rust treatment: �50-�150
• Welding repairs: �200-�800 (depending on extent)
• Sill replacement: �400-�1,000 per side
• Chassis repair: �500-�2,000+

Warning: Serious structural rust can be economically unviable to repair on older vehicles.

#9: Mirrors

Why It Fails:

• Missing mirror - Driver's side mirror is mandatory, passenger and interior also required
• Broken or cracked glass - Obscuring vision
• Insecure mounting - Mirror not firmly attached
• Incorrect adjustment - Electric mirrors must work

Requirements

Must have:

• Driver's door mirror
• Either passenger door mirror OR interior mirror
• All mirrors must be secure and provide clear view

Quick Fixes

• Replace missing stick-on mirror: �10-�30
• Secure loose mirror: Tighten screws or re-glue
• Replace broken glass: �15-�50 (DIY) or �50-�150 (fitted)

#10: Registration Plates

Why It Fails:

• Illegible characters - Dirt, damage, or fading
• Wrong font or spacing - Non-compliant style
• Incorrect size - Letters/numbers not standard size
• Reflectivity issues - Plate not reflective
• Insecure mounting - Plate loose or missing fixing
• Damage or cracks - Broken or bent plate

MOT Requirements

Legal plates must have:

• Charles Wright font (standard UK font)
• Correct spacing - No custom spacing
• Black characters on white (front)
• Black characters on yellow (rear)
• No borders, flags, or badges (except GB identifier or Union flag)
• Reflective material
• Secure mounting - Top and bottom fixings

Common Mistakes

L "Show plates" (incorrect font/spacing) - FAIL L Custom spacing - FAIL L Cracked or broken - FAIL L Faded or dirty - May fail if illegible

Replacement Cost

New registration plates: �10-�25 (pair)

• Available from Halfords, garages, online suppliers
• Must show supplier postcode on plate
• Requires V5C document to prove ownership

5-minute fix: Clean dirty plates with soapy water. Many failures are simply due to mud obscuring numbers.

How to Avoid MOT Failures

Pre-MOT Inspection Checklist

2 weeks before MOT, check:

 All lights working (walk around test)  Tyre tread depth (20p test all four tyres)  No warning lights on dashboard  Windscreen wipers work (no streaking)  Washer fluid topped up  Brake pedal firm feel  Handbrake holds on a hill  Horn works  All seatbelts present and click  Mirrors all present and secure  Number plates clean and legible  No obvious exhaust smoke

Download Complete MOT Checklist �

Book MOT Early

• Don't wait until last minute - If you fail, you need time to fix and retest
• Book 1 month in advance - Keeps your expiry date for next year
• Avoid rush periods - March and September are busiest

Address Previous Advisories

Check your MOT history for advisory items from last year. These often become failures the next year.

Check Your MOT History Free � - See your advisories and plan repairs

Regular Servicing

Cars that are regularly serviced are far more likely to pass:

• Oil changes keep engine healthy (helps emissions)
• Filters replaced improve performance
• Fluids topped up
• Small issues caught before they become failures

Pre-MOT Garage Inspection

Some garages offer pre-MOT inspections for �20-�40:

• Identify potential failures before official test
• Get quotes for repairs
• Time to shop around for best prices
• Worth it for older vehicles or if you're concerned

Use MOT History to Predict Failures

Your vehicle's MOT history can reveal patterns:

Recurring advisories = Likely future failures

• Brake wear mentioned 3 years running? They'll fail soon
• Tyre wear noted? Budget for replacements
• Corrosion advisories? Getting worse each year

Mileage trends = Maintenance needs

• High annual mileage? Brakes and tyres wear faster
• Low mileage? Check for perished rubber and seized components

Our mileage chart shows:

• Usage patterns over time
• Mileage at each test
• Potential clocking (fraud detection)

Check Your Free MOT History & Mileage Chart �

MOT Failure FAQ

What is the most common MOT failure?

Lighting and electrical equipment failures account for 23.64% of all defects, making them the most common reason for MOT failures. Blown bulbs alone cause thousands of failures that could be avoided with a simple �5 bulb replacement.

How can I avoid failing my MOT?

The best way to avoid MOT failure is to check your car 2 weeks before the test using our checklist. Walk around testing all lights, check tyre tread depth, top up washer fluid, and address any dashboard warning lights. Most failures are preventable.

What fails an MOT immediately?

Dangerous defects cause immediate failure, including: excessive brake wear, bald tyres, serious structural corrosion near seatbelt mounts, missing lights, severely cracked windscreen, or steering with excessive play. These pose immediate safety risks.

Can I fix failures myself?

Many common failures are DIY-fixable: replacing bulbs, topping up fluids, cleaning number plates, replacing wiper blades. However, brake work, suspension repairs, and emissions issues usually require professional mechanics.

How much does it cost to fix MOT failures?

Costs vary widely:

• Minor (bulbs, wipers): �10-�50
• Moderate (brake pads, tyres): �100-�300
• Major (suspension, exhaust): �200-�800
• Serious (structural rust, DPF): �500-�2,000+

Budget �100-�200 for typical failures on a well-maintained car. Neglected vehicles can easily cost �500-�1,000 to put right.

Check Your MOT History Before Your Test

The smartest way to prepare for your MOT is to check your vehicle's complete history first. Our free MOT checker shows:

 Previous failures - Know what failed before  Advisory items - Track recurring issues  Mileage progression - Spot maintenance needs  Test dates - Plan your next test

Don't wait until you fail - check your history today and address potential issues early. A �10 bulb replacement now beats a �54.85 retest fee plus the cost of fixing failures.

Check Your Free MOT History Now � (Enter your registration for instant results)

Remember: 40% of cars fail their MOT, but most failures are preventable. With this guide and a simple pre-MOT check, you can join the 72% who pass first time.