For most drivers in the UK, an MOT test is required once a vehicle is more than 3 years old. Designed to ensure cars remain roadworthy and safe, the MOT checks a wide range of components, from tyres and brakes to lights and emissions.
Unfortunately, many drivers fail their MOT every year, often because issues could have been identified and fixed beforehand. Understanding the most common MOT fail reasons can help you prepare your vehicle properly, reduce unexpected repair costs, and improve your chances of passing first time.
In this guide, we’ll explain what an MOT failure is, what you can fail an MOT on, how to avoid common MOT failures, and what to do if your vehicle doesn’t pass.
What is an MOT failure?
An MOT failure means your vehicle did not meet the minimum legal road safety and environmental standards required during its MOT inspection.
When a car fails its MOT, the garage will issue a VT30 certificate listing the faults found during the test. Faults are categorised into three main groups:
Dangerous faults.
Major faults.
Minor faults.
Dangerous and major faults result in an MOT fail, while minor faults are usually issued as advisory notices and should still be addressed as soon as possible. If your vehicle displays a dangerous fault, it may not be legal to drive it away from the test centre until repairs are completed.
What can you fail an MOT on?
There are many things that can result in an MOT fail, but most failures stem from a handful of common issues. These often involve parts of the vehicle that naturally wear over time or are overlooked during routine maintenance.
Some of the most common MOT failures include:
Faulty lights.
Brake problems.
Suspension issues.
Poor visibility.
Emissions problems.
Damaged windscreen wipers.
Registration plate issues.
Many of these problems are relatively simple to spot before your test and can often be fixed quickly and cheaply.
The most common MOT failure reasons
Faulty lights and indicators
Lighting issues are among the leading causes of MOT failure in the UK. This includes:
Broken headlights.
Faulty brake lights.
Non-working indicators.
Reversing lights.
Number plate lights.
In many cases, drivers simply aren’t aware that a bulb has gone out.
Before your MOT, walk around your vehicle and check that every light is working correctly. Ask someone to help check brake lights and indicators if needed. Simple bulb replacements are usually inexpensive compared to the inconvenience of an MOT fail.
Tyre condition and tread depth
Tyres play a major role in vehicle safety, particularly in wet or icy conditions.
The legal minimum tread depth in the UK is 1.6mm across the central three-quarters of the tyre, but tyres can still perform poorly before reaching this limit.
Your tyres may fail an MOT if they have:
Insufficient tread depth
Cuts or bulges
Uneven wear
Exposed cords
Incorrect tyre sizes
Regular tyre inspections can help you identify problems early. Keeping tyres inflated to the correct pressure can also reduce wear and improve fuel efficiency.
Brake problems
Brakes are another major contributor to common MOT failures. Since brakes are essential to road safety, even minor issues can lead to failure.
Common brake-related MOT fail reasons include:
Worn brake pads.
Damaged discs.
Brake imbalance.
Fluid leaks.
Reduced braking performance.
Drivers may notice warning signs such as squealing noises, vibrations, or longer stopping distances before problems become serious.
Routine servicing is one of the best ways to catch brake issues early, which is why regular car and van servicing matters to all drivers.
Windscreen damage and visibility issues
Your visibility must not be impaired during driving, which means the MOT includes checks on:
Windscreens.
Wipers.
Washers.
Mirrors.
A chip or crack in the driver’s line of sight could result in an MOT fail, depending on its size and location.
Worn wiper blades are another common issue. If wipers smear water or fail to clear the windscreen effectively, they may need replacing before the test. It’s also important to ensure your washer fluid is topped up before arriving at the garage.
Suspension and steering faults
Suspension problems are especially common on vehicles regularly driven over potholes or rough roads.
Issues may include:
Broken springs.
Damaged shock absorbers.
Excessive movement.
Steering wear.
Drivers sometimes notice knocking sounds, uneven tyre wear, or poor handling before these faults are identified during an MOT. Because suspension repairs can become expensive if left unresolved, regular maintenance checks are essential.
Emissions and exhaust problems
Modern MOT tests include strict emissions checks to ensure vehicles meet environmental standards. Common emissions-related MOT fail reasons include:
Exhaust leaks.
Faulty catalytic converters.
Diesel particulate filter (DPF) issues.
Excess smoke emissions.
Short journeys and infrequent motorway driving can sometimes contribute to DPF problems in diesel vehicles. If your engine warning light is illuminated before the MOT, it’s best to investigate the issue immediately rather than risk a failed test.
Registration plate problems
Registration plates must be clearly visible and correctly formatted.
You could fail an MOT if your plate is:
Dirty or unreadable.
Cracked or damaged.
Incorrectly spaced.
Missing required markings.
This is one of the easiest MOT fail reasons to avoid, yet it still catches many drivers out every year.
How to avoid an MOT fail
Preparing your vehicle before its MOT can significantly improve your chances of passing first time. Some simple checks you can carry out include:
Check all lights: Test headlights, indicators, brake lights, fog lights, and number plate lights before your appointment.
Inspect tyres: Check tread depth, tyre pressure, and look for visible damage.
Top up fluids: Ensure oil, coolant, and washer fluid levels are correct.
Replace worn wipers: If wipers leave streaks or squeak excessively, replace them before the test.
Clear warning lights: Dashboard warning lights can result in an MOT fail, particularly engine management or ABS warnings.
Listen for unusual noises: Knocking, squealing, or grinding sounds may indicate developing mechanical issues. Taking a few minutes to inspect your car beforehand can prevent unnecessary repair bills and delays.
For additional preparation advice, many drivers benefit from reading top tips for passing your MOT first time before booking their test.
What to do if your car fails its MOT
Failing an MOT can be frustrating, but it doesn’t always mean major repairs are needed. If your vehicle fails:
Review the fault report: The garage will explain the reasons for the MOT failure and provide a list of faults.
Understand the severity: Minor issues may simply need quick repairs, while dangerous faults could prevent you from legally driving the vehicle.
Arrange repairs: You can often have repairs completed at the same garage or choose another repair centre.
Book a retest: In many cases, you can receive a partial or free retest if repairs are completed within a certain timeframe.
Avoid driving illegally: If your MOT has expired and the vehicle has dangerous faults, you may only be allowed to drive it directly to a repair appointment.
Planning ahead can help minimise disruption and reduce the risk of unexpected downtime, especially for businesses managing multiple vehicles. This is why planning ahead for MOTs, servicing, and vehicle downtime can make a significant difference.
Do garages fail MOT on purpose?
Some drivers wonder whether garages fail vehicles intentionally to generate repair work. While this concern exists, MOT testing in the UK is tightly regulated by the DVSA.
Approved MOT testing stations must follow strict inspection guidelines, and testers are regularly monitored to ensure standards are maintained. Most garages do not fail vehicles unnecessarily. In fact, many failures involve straightforward issues that genuinely affect safety or legality.
If you disagree with an MOT result, you can appeal through the DVSA, though you should avoid carrying out repairs beforehand if you intend to challenge the decision.
Why MOT preparation matters
An MOT isn’t just a legal requirement; it’s an important safety check that helps identify potentially dangerous issues before they become serious.
Preparing your vehicle properly can help:
Reduce repair costs.
Improve vehicle safety.
Minimise unexpected breakdowns.
Avoid unnecessary downtime.
Increase the likelihood of passing the first time.
Even basic maintenance checks can make a significant difference when MOT season arrives.
Frequently asked questions about how to avoid MOT fails
What is the most common MOT fail?
Lighting faults are consistently among the most common MOT fails in the UK, followed closely by tyre and brake issues.
Can I drive my car after an MOT fail?
This depends on the severity of the fault and whether your previous MOT is still valid. Dangerous faults may make the vehicle illegal to drive.
How much does it cost to retest an MOT?
Some garages offer free retests if repairs are completed within a set timeframe, while others may charge a reduced fee.
How can I check if my car is due for an MOT?
You can check your MOT status and expiry date online using the GOV.UK MOT checker service.
Can worn tyres fail an MOT?
Yes. Tyres with tread below the legal depth or visible damage can result in an MOT fail.
Will an engine warning light fail an MOT?
Yes. Certain warning lights, including engine management, ABS, and airbag lights, can cause an MOT failure.
Do advisory notices fail an MOT?
No. Advisory notices do not fail the MOT, but they highlight issues that may need attention soon.
How long does an MOT test take?
Most MOT tests take between 45 minutes and one hour, depending on the vehicle and whether faults are identified.
