Top 10 MOT Failure Reasons and How to Avoid Them in 2026

Discover the top 10 MOT failure reasons and simple ways to avoid them. Save time, money and stress with these expert tips before your next MOT test.

What the MOT Test Is Really Checking

Most drivers treat the MOT as something that just happens once a year, a box to tick, a certificate to collect. But underneath that routine sits a rigorous safety inspection that checks dozens of components across your vehicle, from your lighting to your tyres, brakes to emissions. Understanding what the test is looking for puts you in a much stronger position to pass it.

The MOT was introduced to protect everyone on the road, not just the driver. A car with worn brake pads or a cracked windscreen is not just a risk to you, it is a risk to the pedestrian crossing in Farnborough town centre or the cyclist on a back road through Tongham. The test exists for good reason, and failing it is more common than most people realise.

What Are the Most Common MOT Failure Reasons?

According to DVSA MOT testing data, the most common MOT failure reasons are:

1. Faulty lights and indicators
2. Worn or damaged tyres
3. Brake defects
4. Suspension problems
5. Windscreen and wiper issues
6. Excessive emissions
7. Exhaust system faults
8. Steering defects
9. Damaged seat belts
10. Illegal or damaged number plates

Most MOT failures can be avoided through routine vehicle maintenance, regular tyre inspections, brake checks, and a pre-MOT inspection before test day.

10 Common MOT Failure Reasons (And How to Prevent Each One)

This section covers each failure point in detail, ranked by frequency based on government MOT test data. Whether your car is due in Aldershot next week or Farnham in two months, the same rules apply.

1. Lighting and Signalling Faults

Lighting faults are consistently the number one cause of MOT failures across the UK. A single blown bulb, even a rear fog light that rarely gets used, is enough to earn a fail.

Testers check every external light on the vehicle: headlights, brake lights, indicators, fog lights, reversing lights, hazard lights and number plate illumination. If it does not work, it fails.

What to do:

1. Walk around your car at night and check all lights are functioning before your test.
2. Ask a friend to stand behind the car while you press the brake pedal.
3. Check that headlights are properly aligned, misalignment is also a testable item.
4. Replace any blown bulbs at least a week before your MOT so you have time to double-check.

Did you know? According to government test data, lighting and signalling defects account for approximately 30% of all recorded MOT failure items, making it the single largest category year after year.

Light Type	Common Fault	How to Check
Headlights	Blown bulb or misalignment	Switch on, check both beams
Brake Lights	Bulb failure	Press pedal, ask someone to watch
Indicators	Not flashing or too fast/slow	Activate and walk around car
Number Plate Light	Often forgotten	Check at night
Fog Lights	Inoperative switch or bulb	Test front and rear separately

2. Tyre Condition and Tread Depth

Tyres are where your car meets the road. They are arguably the most safety-critical component on any vehicle, and yet they are one of the most neglected. Tyre failures at MOT come in several forms: insufficient tread depth, visible damage such as cuts or bulges, incorrect tyre size, or tyres in a condition deemed structurally unsafe.

The legal minimum tread depth in the UK is 1.6mm across the central three-quarters of the tyre width. However, most tyre professionals recommend replacing tyres at 3mm, as stopping distances increase significantly below that threshold.

Residents across Fleet, Ash Vale and North Camp who cover longer daily commutes tend to wear tyres faster, so checking tread regularly makes sense regardless of when your MOT falls.

What to check before your MOT:

1. Use a 20p coin inserted into the tread groove, if the outer band of the coin is visible, you are likely below the legal limit.
2. Inspect sidewalls for bulges, cuts or cracking.
3. Check that all four tyres are the same size and type as required by the vehicle manufacturer.
4. Ensure valve caps are present and tyres are inflated to the correct pressure.

If you are unsure about your tyre condition, a pre-MOT tyre check at G Force Tyres can identify any concerns before test day.

Tread Depth	Status	Recommendation
3mm or above	Good	Monitor regularly
2mm to 3mm	Monitor	Plan replacement soon
1.6mm to 2mm	Legal but worn	Replace immediately
Below 1.6mm	Illegal	Replace before MOT

3. Brakes

Brake defects are among the most serious failure categories an MOT tester can record. A brake fault is not just a test failure, it is a genuine safety emergency. Worn brake pads, corroded discs, fluid leaks, or a handbrake that fails to hold the vehicle correctly can all result in a fail.

Brake fade, spongy pedal feel and pulling to one side when braking are all warning signs that something is wrong before the MOT even arrives. Do not wait for the tester to tell you what you already suspect.

Common brake-related failure points:

1. Brake pads worn below the minimum thickness.
2. Brake discs that are heavily scored, corroded or warped.
3. Handbrake that fails the efficiency test.
4. Brake fluid that has degraded or is leaking.
5. Uneven braking force between wheels, causing the car to pull.

If your car has been sitting on a driveway in Ash or Farnborough for a few weeks over winter, disc corrosion can develop faster than you might expect, particularly on vehicles not driven regularly. A visual check or a short test drive will often reveal brake issues before the test date.

4. Suspension Components

The suspension system absorbs shocks from the road, maintains tyre contact and keeps your vehicle stable. When components fail, handling becomes unpredictable, and the MOT tester will flag it.

Suspension failures typically involve worn shock absorbers, damaged springs, deteriorated bushes or loose anti-roll bar drop links. These parts degrade gradually, which means drivers often adapt to the symptoms without realising the vehicle is no longer safe.

Signs your suspension may be failing:

1. The car bounces excessively after going over a speed bump.
2. You hear knocking or clunking from underneath the car on uneven roads.
3. The car dips heavily at the front when braking.
4. Uneven tyre wear across the tread pattern.

Winding country roads between Tongham and Farnham put genuine stress on suspension components, particularly on older vehicles. Regular servicing helps catch these issues before they become a test failure.

Component	Warning Sign	Failure Risk
Shock Absorbers	Excessive bounce	High
Springs	Sagging ride height	High
Bushes	Knocking, vibration	Medium
Anti-roll bar links	Clunking on corners	Medium
Wheel bearings	Humming noise	High

 

5. Driver’s View of the Road (Windscreen and Wipers)

A chip, crack or screen damage that falls within the tester’s defined zones can cause an immediate failure. The windscreen is divided into specific areas, damage directly in the driver’s line of sight is treated very seriously, while damage further out may only result in an advisory.

Wiper blades that smear rather than clear, or washers that fail to produce a jet of fluid, are also testable items. These are among the easiest pre-MOT checks to carry out.

Simple pre-MOT checks:

1. Inspect the windscreen carefully for chips or cracks, especially in the swept area of the wipers.
2. Test wiper blades at all speeds, including intermittent settings.
3. Top up the washer reservoir and confirm jets are directed at the screen correctly.
4. Check that the rear windscreen and heated elements are working.

A small chip picked up on the A31 near Farnham can turn into a spreading crack within weeks, particularly in cold or wet conditions. Getting it repaired promptly not only prevents an MOT fail but is far cheaper than a full screen replacement.

6. Emissions

Exhaust emissions testing is a core part of the MOT, and it catches a surprising number of vehicles every year. The test measures the levels of harmful gases produced by the engine — and a car that is running inefficiently, burning oil or running on a faulty catalytic converter will produce readings that breach the legal limits.

Diesel vehicles in particular are tested for visible smoke, and any dark or excessive exhaust output will result in a fail. This is particularly relevant for older diesel cars that may have had their diesel particulate filter (DPF) removed or blocked.

What can cause an emissions failure:

1. A faulty or missing catalytic converter.
2. A blocked or removed DPF on diesel vehicles.
3. Engine running too rich (too much fuel relative to air).
4. Oil burning due to worn piston rings or valve seals.
5. Failing oxygen sensors sending incorrect fuel mixture data to the engine management system.

Making sure your car has had a full service before the MOT is one of the most reliable ways to reduce emissions-related risk. Fresh oil, a clean air filter and a correctly functioning fuel system all contribute to lower emissions output.

Emissions failure at a glance:

Vehicle Type	What Is Tested	Common Cause of Failure
Petrol	CO, HC, Lambda	Faulty catalytic converter
Diesel	Smoke opacity, PM	Blocked or removed DPF
Hybrid	Both standards apply	Battery/engine balance issues

 

7. Fuel and Exhaust System

Beyond emissions output, the physical condition of the fuel and exhaust system is also inspected. Leaking fuel lines, corroded exhaust pipes, broken mountings or a damaged silencer are all failure items, and some of them create noise long before they become test issues.

A blowing exhaust is one of the more obvious warning signs, but a small fuel leak is far more dangerous and far harder to spot. If you notice a smell of petrol inside the cabin or after parking, it should be investigated immediately, not just for the MOT, but for your personal safety.

Practical checklist:

1. Listen for any unusual exhaust noise, especially under acceleration.
2. Check exhaust mountings are secure and not hanging loose.
3. Look for visible corrosion along the exhaust pipe system.
4. If you detect any fuel smell, have the system inspected before driving further.

8. Steering

Steering failures at MOT typically involve excessive play in the steering wheel, worn joints, damaged steering racks or seized components. A small amount of play in older vehicles may be acceptable, but a tester who finds the steering wheel moves significantly before the wheels respond will record a defect.

Power steering fluid leaks, damaged steering columns or worn track rod ends all fall within this category. Drivers who notice their steering feeling heavy, inconsistent or pulling to one side should treat that as an urgent signal, not just a nuisance.

What gets checked:

1. Steering wheel free play, how much it moves before the wheels respond.
2. Condition of track rod ends, ball joints and steering rack.
3. Power steering fluid levels and signs of leakage.
4. Steering lock operation and column integrity.

9. Seat Belts and Restraints

Seat belts are a legal requirement and an MOT testable item. Testers check that belts retract smoothly, lock correctly under load, are securely anchored and show no signs of fraying or damage. A belt that jams, fails to retract, or whose buckle does not click securely will cause a fail.

This is one of the easiest pre-MOT checks to carry out, and one that is often overlooked because drivers assume the belt is fine simply because it clicks shut.

Check every belt in the car:

1. Pull each belt fully out and check for fraying, cuts or discolouration.
2. Allow it to retract: it should wind back smoothly without bunching.
3. Buckle and release each clasp to confirm the mechanism works properly.
4. Check rear seat belts too: they are equally testable.

10. Number Plates

It might seem minor, but a number plate that is cracked, faded, incorrectly spaced or not meeting legal character requirements is enough to generate a failure. The plate must be clearly legible, properly lit and securely fixed to the vehicle.

Personalised plates with stylised fonts or altered character spacing are a common trap, if the spacing does not comply with legal standards, it is a failure regardless of how it looks.

What to check:

1. Both plates are present, clean and undamaged.
2. Characters are the correct legal size, font and spacing.
3. The rear plate is illuminated by a functioning light.
4. Plates are secure and not cracked or obscured.

Understanding MOT Failure Categories

Not every MOT defect is treated equally. The test uses a three-tier system to communicate the severity of each item found, and understanding these categories helps you make informed decisions after a test.

You can read a full breakdown of how each category works in this guide to MOT fail categories explained.

Category	What It Means	Can You Drive Away?
Dangerous	Poses immediate risk to road safety	No: illegal to drive
Major	Significant risk: vehicle has failed	No: must be repaired
Minor	Advisory only: vehicle passes	Yes: but repair soon

A Dangerous item means the vehicle presents an immediate hazard. A Major item means the vehicle has failed and must be repaired before being used on the road. A Minor item is recorded as an advisory, the car passes, but the issue should be addressed before the next test.

Electric Vehicles and MOT Failures: What Is Different

If you drive an electric vehicle, the MOT process shares much of the same structure as a conventional car, but there are some key differences. The combustion-related checks simply do not apply, but the test still covers tyres, brakes, lights, steering, suspension and structural integrity.

Electric cars can also fail for issues specific to their drivetrains, such as exposed high-voltage cables, missing warning labels or damaged battery enclosures. For a detailed breakdown of what EV owners need to know, this guide on electric car MOT failures covers the full picture.

How to Prepare Your Car Before MOT Day

Preparation is not about gaming the system, it is about making sure your vehicle is in the condition it should already be in year-round. A simple walk-around check the week before your test can prevent the majority of first-time failures.

A practical pre-MOT checklist:

1. Check all exterior lights: front, rear, indicators, fog, number plate.
2. Inspect all four tyres for tread depth, damage and correct pressure.
3. Test all seat belts for smooth operation and secure fastening.
4. Top up washer fluid and test wipers on all settings.
5. Check the windscreen for chips or cracks in the swept area.
6. Look for any warning lights on the dashboard: address them before the test.
7. Listen for any unusual noises from brakes, suspension or exhaust when driving.
8. Confirm the number plates are clean, undamaged and correctly formatted.
9. Check the handbrake holds the vehicle on a slope.
10. If your car is diesel, check for any visible exhaust smoke under acceleration.

Running through this checklist costs nothing but a few minutes of your time. Drivers across North Camp, Ash Vale and Farnborough who take this approach rarely arrive at the test with surprises waiting for them.

What Happens If You Fail Your MOT?

A first-time fail is not the end of the world. What matters most is understanding what has been found, what category it falls into and what your options are.

If your vehicle fails on a Major or Dangerous item, it cannot be driven on public roads until repaired, unless you are driving directly to a pre-booked repair appointment. Once repairs are complete, the vehicle can be retested. If the retest takes place at the same garage within ten working days, some garages will offer a partial or full retest at a reduced or no additional charge, though this varies by provider.

Do not be tempted to ignore a failed MOT. Driving a vehicle without a valid certificate is a criminal offence and can invalidate your insurance, meaning that in the event of an accident, you would bear the full financial consequences yourself.

MOT Failure Statistics UK

Recent DVSA data shows:

• Nearly 30% of MOT failures are caused by lighting and signalling defects.
• Tyres and braking systems remain among the most dangerous MOT failures.
• More than 2 million vehicles fail MOT tests annually due to tyre-related defects.
• Suspension and steering faults account for a significant proportion of dangerous MOT advisories.
• Vehicles that receive regular servicing are considerably more likely to pass their MOT first time.

Conclusion

The MOT test is not designed to catch you out, it is designed to keep you, your passengers and everyone around you safe. The ten failure points covered in this guide account for the overwhelming majority of vehicles that do not pass first time, and almost all of them can be identified and addressed in advance with a simple, methodical pre-check.

Whether you drive through Aldershot daily, commute from Farnham or park up in Fleet, your vehicle is subject to the same road conditions and the same legal requirements. A little attention before test day pays dividends in time saved, stress avoided and money kept where it belongs, in your pocket.

Frequently Asked Questions

What is the most common reason for MOT failure?

Lighting and signalling faults are the most frequently recorded category in MOT failure data, accounting for roughly a third of all recorded defects. A single blown bulb is enough to fail the test, which is why a quick light check before your appointment matters.

Can I drive my car if it fails the MOT?

If your existing MOT certificate has expired, you cannot legally drive the vehicle on public roads following a failed test, unless you are driving directly to a pre-booked repair. If your certificate is still valid and the failure is not in the Dangerous category, different rules may apply. Always confirm with your garage.

How long does an MOT test take?

A standard MOT test typically takes between 45 minutes and one hour. If additional checks are needed or advisory items need discussion, it may take slightly longer.

Is it worth getting a service before an MOT?

Yes, a full service before an MOT addresses many of the issues that commonly cause failures, including oil condition, filter cleanliness, fluid levels and general mechanical health. It is one of the most effective ways to increase your chances of a first-time pass.

Do electric cars need an MOT?

Yes. Once an electric vehicle is three years old, it requires an annual MOT just like any other car. The test covers all non-drivetrain components plus specific EV safety checks.

What is the difference between a Major and Dangerous MOT failure?

A Major failure means the vehicle has failed the test and must be repaired before use. A Dangerous failure means the vehicle poses an immediate risk and cannot be driven legally at all until the issue is resolved.

Can I get an MOT retest for free?

Some garages offer a free or reduced-cost partial retest within a set number of working days if repairs are carried out with them. The terms vary, so it is always worth asking at the time of booking.