Written by the MOT Check Now editorial team and checked against GOV.UK and DVSA guidance. Last updated 3 November 2026. Read our editorial policy and how we get our data.
MOT failure reasons come down to a fairly short list of areas of the car. The test is a roadworthiness inspection, and the tester works through the vehicle’s safety-related systems and records anything that does not meet the standard. This guide walks through the main areas the test examines, shows which checks an owner can do at home in a few minutes, explains the difference between a fail and an advisory, and tells you where to go next if the result is not what you hoped for.
We do not publish “most common failure” league tables here, because we would not be able to back them with an official source we can quote. What we can give you is an accurate picture of what is examined and a practical way to check each area before the test.
Quick answers
- The MOT covers lights, brakes, steering, suspension, tyres, wheels, seatbelts, exhaust and emissions, visibility, bodywork, the fuel system and the registration plate and VIN.
- A fail is caused by a major or a dangerous defect. Minor defects and advisories are on a pass.
- Many failures come from items you can check at home in minutes: bulbs, wipers, tyres, the horn, mirrors, seatbelts, the fuel cap and the number plate.
- The legal minimum tyre tread depth for a car is 1.6mm across the central three-quarters of the tread, around the whole tyre.
- The test is not a check of the engine, clutch or gearbox, and it is not a service.
- After a fail, you can drive away only if your current MOT is still valid and no dangerous defect was listed.
Key facts at a glance
| Topic | What to know |
|---|---|
| What the test is | A roadworthiness inspection of safety and environmental items on the day |
| How long it takes | Roughly 45 to 60 minutes for a car |
| Maximum fee for a car | £54.85, no VAT charged, and garages may charge less |
| Defect categories | Dangerous, major, minor, advisory and PRS, in use since 20 May 2018 |
| Causes of a fail | Dangerous and major defects |
| Minimum tread depth for cars | 1.6mm across the central three-quarters of the tread, around the whole circumference |
| Penalty for driving with a dangerous defect | Fine up to £2,500, driving ban and 3 penalty points |
| Free partial retest | Car left at the test centre and retested within 10 working days |
| Appeal deadline for a failed vehicle | 14 working days to send the complaint form to DVSA |
What the MOT test examines
An MOT looks at the condition of the vehicle on the day. It is not a check of the engine’s long-term health or the clutch, and it is not a service. The broad areas are below. The detailed test manual is much longer, so treat this as a map and not a full list.
- Lights, indicators and reflectors
- Brakes
- Steering
- Suspension
- Tyres
- Wheels
- Seatbelts
- Exhaust and emissions
- Visibility, including wipers, washers, mirrors and the windscreen
- Bodywork condition
- Fuel system
- Registration plate and vehicle identification number (VIN)
Each area is covered in more detail below, with the kind of fault that can lead to a fail and a check you can do yourself where one is practical. The tester also looks at other items that sit alongside these, such as the horn, the doors and their latches, the security of seats and the battery, and dashboard warning lights for important safety systems. The full list is set by DVSA, and the explanation of the test items in the MOT test checklist goes into each one.
Why the same few areas keep appearing
Parts that wear in normal use are the ones that reach the limit between tests. Bulbs blow, wiper blades perish, tyres wear down, brake pads and discs thin and rubber bushes harden. These are consumable items, and a year of driving is long enough to take any of them past the standard. The other group is parts that fail through age or weather, such as corrosion in structural areas and perished hoses. Understanding this helps you think about your own car: it tells you where to look first and which items you can replace cheaply before the test.
It also explains why we do not rank failure reasons. A ranking would imply a precision that we cannot source, and the list that matters is the one for your car, which depends on its age, mileage and how it is used. The best guide is its own record. The free MOT history shows what failed and what was noted on past tests, and the advisory tracker shows whether those advisories were dealt with.
Lights, indicators and reflectors
Testers check that the lamps work, are the right colour, are secure and aim correctly. That includes dipped and main beam headlights, sidelights, brake lights, indicators, hazard lights, fog lights and the rear number plate light. A bulb that has blown is a straightforward fault, and one of the cheapest things to put right before a test.
Check at home: switch everything on and walk around the car. For brake lights, reverse towards a wall or shop window at night, or ask someone to watch while you press the pedal. Check that lenses are not cracked or full of water.
Typical wording (illustrative): “nearside dipped beam not working”, “rear registration plate lamp inoperative”, “headlamp aim too high”. The category depends on how serious the effect is, and a single failed bulb is usually a straightforward, inexpensive repair. Because these items are quick to fix, they are the ones most likely to qualify for the free retest by the end of the next working day if you return to the same test centre.
Brakes
The brakes are tested for effectiveness and balance, and the tester also looks at the condition of components such as discs, pads, pipes and hoses where they are visible, along with the handbrake. Weak or uneven braking, a leaking hose or a corroded pipe are the sort of defects that can turn into a major or dangerous fault.
Check at home: notice whether the pedal feels spongy or goes close to the floor, whether the car pulls to one side under braking, and whether you hear grinding or squealing. The handbrake should hold the car on a slope without needing to be pulled to its highest notch. If you notice a change in how the brakes feel, get them looked at before the test and not after it.
Typical wording (illustrative): “brake disc worn, pitted or scored”, “brake pipe corroded”, “handbrake lever has excessive travel”. Brake defects are among the ones most likely to be recorded as dangerous when severe, because the risk is immediate. If you have any doubt about your brakes, do not wait for the test.
Steering
Steering is checked for play, smoothness and condition of the parts that connect the wheel to the road. Excess movement in the wheel, stiff steering or a worn joint can all be recorded. A tester will also look at power steering fluid leaks where they are visible.
Check at home: with the car stationary and the engine running if you have power steering, turn the wheel gently and notice any vague or notchy feel. Listen for knocking when turning at low speed.
Typical wording (illustrative): “steering rack ball joint dust cover split”, “excessive play in steering linkage”. A split gaiter or boot is a common advisory because it lets dirt in and wears the joint underneath. If it is replaced early, it is a cheaper job than waiting for the joint to wear.
Suspension
Springs, shock absorbers, bushes and joints are inspected for damage, leaks and wear. A broken spring or a badly worn joint can fail a test. Suspension faults often show up gradually as a bouncy ride, noises over bumps or uneven tyre wear, which is why they commonly appear first as advisories in older cars.
Check at home: park on level ground and look for the car sitting lower at one corner. Press down firmly on each corner and release; a healthy corner settles quickly. Look at tyre wear patterns, since uneven wear can point to suspension or alignment problems.
Typical wording (illustrative): “shock absorber leaking fluid”, “coil spring broken”, “suspension arm bush worn”. Where a shock absorber is leaking, the tester is looking at whether the leak is slight or excessive. A slight leak may be an advisory, and an excessive one can fail the test.
Tyres and wheels
Tyres are checked for tread depth, condition and suitability. The legal minimum tread depth for a car is 1.6mm across the central three-quarters of the tread, around the whole circumference. Cuts, bulges, exposed cords and similar damage can all be recorded. Wheels are checked for damage, security of fixings and condition of the rim.
Check at home: a tread depth gauge gives a reading in millimetres and costs very little. Many drivers use the 20p coin as a rough check, which is a common practice, but a gauge is more accurate and the legal limit is a measurement and not a coin. Also look along the sidewalls for cracks and lumps, check the tyre pressure. Make sure all the wheel nuts are present.
Typical wording (illustrative): “tyre tread depth below requirements of 1.6mm”, “tyre has a bulge in the sidewall”, “wheel nut missing”. Tyres are a good example of how an advisory turns into a fail: a tyre noted as close to the legal limit one year is likely to be below it the next. Our tyre guide explains tread depth, condition, age and how to read the sidewall markings.
Seatbelts
Every belt is checked for condition, security of mounting and correct operation of the buckle and retractor. Frayed webbing, belts that do not retract or buckles that do not latch can cause a fail.
Check at home: pull each belt out fully, look for fraying or cuts, let it retract, and click each buckle in and out. Tug sharply on the belt to check it locks. This takes a minute per seat and is one of the quickest checks on this page.
Exhaust and emissions
The exhaust is checked for leaks, security and the condition of the system, and emissions are measured. The limits depend on the fuel type and the age of the vehicle. A leaking exhaust is usually noisy, which is your first clue. Diesel vehicles may also be checked for smoke from the exhaust.
Check at home: listen for a louder-than-normal note and look underneath for loose or hanging sections. Visible blue or black smoke in normal driving suggests an emissions problem to deal with before test day. Do not ignore a warning light on the dashboard, particularly ones related to the engine or exhaust system.
It helps to know that emissions are a separate matter from emissions zones. The MOT emissions test is about whether your vehicle meets the standard that applies to its age and fuel type. ULEZ and Clean Air Zones are local charging schemes that use the vehicle’s Euro status and fuel type. A car can pass its MOT and still be chargeable in a zone. Our ULEZ checker and Clean Air Zone checker estimate zone status from the data, and you should always confirm with the official operator.
Visibility: wipers, washers, mirrors and the windscreen
The driver must be able to see clearly. Testers check that wiper blades clear the screen effectively, that the washers work, that mirrors are secure and not badly damaged, and that the windscreen is free from damage or obstruction in the area directly in the driver’s view. A large crack or a chip in the swept area directly in front of the driver is the typical cause of a fail.
Check at home: run the wipers on a damp windscreen and see if they smear or judder. Top up the washer fluid and make sure the jets spray onto the glass. Look at the windscreen from the driver’s seat for chips and cracks, and make sure nothing hangs from the mirror or blocks the view. Also check that the horn works.
Bodywork condition
The body is not judged for looks. The tester looks for corrosion or damage that affects structural strength or could injure someone, such as sharp edges, or panels in poor condition near major components like suspension mounting points or seatbelt anchorages. Doors should open and close and latch properly.
Check at home: look at the sills, wheel arches and the areas around the suspension mounts. Surface rust that is only cosmetic is different from corrosion that has holed the metal. Check that every door shuts and stays shut.
Corrosion is the failure reason most likely to change the whole repair-or-scrap decision for an older car. A small area of surface rust on a panel is cosmetic, but corrosion in a structural area such as a sill, a subframe or a suspension mounting point can be costly to repair properly, and it tends to spread. If your car has corrosion advisories in its history, take them seriously. The guide to what to do after a failed MOT has a framework for deciding whether to repair.
Fuel system
The fuel system is examined for leaks, secure pipes and a fuel cap that fits and seals properly. A fuel leak is a safety matter and will lead to a serious defect being recorded. Check at home: make sure the fuel cap is present and seals, and look for any smell of fuel or drips under the car.
Registration plate and VIN
Number plates must be secure, in good condition, correctly formed and easy to read. The VIN must be present and match what is recorded. Check at home: clean the plates, check that the characters are not damaged or altered, and that the plate is fixed firmly at both ends. Our number plate guide explains the format.
Other items worth a glance
- Horn. It must work and be loud enough to be heard. Press it before you set off.
- Doors, bonnet and boot. Latches should hold. A bonnet that does not stay closed is a safety matter.
- Seats. The driver and passenger seats should be secure and adjust and lock as designed.
- Battery. It should be secure and free from leaks. A weak battery that struggles to start the car is better dealt with before the test, since a test needs the engine running. Our car battery guide covers testing and replacement.
- Dashboard warning lights. Lights for important safety or emissions systems that stay on after the engine starts are worth investigating, because they can be recorded as defects.
- Towbars. If one is fitted, it must be secure, and the electrical socket should work.
A fifteen-minute pre-test routine
You do not need tools or experience to remove most of the cheap failures. Work through the car in this order, which follows the way you would walk around it.
- Clean the plates and check the lights. Switch on dipped beam, main beam, sidelights, fog lights, indicators and hazards. Walk around the car and check each one, then check the brake lights and the reversing lights.
- Look at the tyres. Measure the tread with a gauge, look for cuts and bulges, check the pressures and count the wheel nuts.
- Test the wipers, washers and horn. Replace worn blades and top up the screenwash.
- Inspect the glass and mirrors. Look for chips in the driver’s view, and make sure the mirrors are secure.
- Try every seatbelt. Pull, release and check the buckle.
- Check the fuel cap, doors and bonnet latch.
- Start the engine. Note any warning lights that stay on, any smoke and any unusual noises.
- Take a short drive. Notice any pulling under braking, vibration, knocking over bumps or strange steering feel.
- Read last year’s advisories. Anything marked then may now be a defect.
For a longer treatment, read how to prepare for an MOT. The routine above is a screen for obvious faults, and it does not replace the test. An item you cannot judge, such as a worn brake component, is best looked at by a garage before the test.
Fail, advisory, minor: what the result means
The result sheet places each defect in one of five categories. Understanding them avoids confusion about whether the car passed.
| Category | Meaning | Result |
|---|---|---|
| Dangerous | Too serious to drive: illegal on the road whether or not an MOT is current | Fail |
| Major | A defect serious enough to fail the test | Fail |
| Minor | Present, but not serious enough to fail | Pass |
| Advisory | Not yet defective but will become so soon | Pass |
| PRS | Defect put right at the test centre during the test | Pass |
The difference between a dangerous and a major defect matters in practice. A major defect means the test is failed and the car needs repair before it passes. A dangerous defect has the added consequence that the car should not be driven away, even if the previous MOT certificate is still in date. Driving a vehicle with a dangerous defect can bring a fine of up to £2,500, a driving ban and 3 penalty points. For the full detail see MOT advisories explained, which includes how each category appears in your history, and MOT defect categories, which explains how testers choose between them.
Worked example: how one defect moves through the categories
Illustrative example. The history below is invented. It shows how a worn front tyre could appear over three years.
| Test | What the tester records | Category | Result |
|---|---|---|---|
| Year 1 | Tread above the limit, no note | None | Pass |
| Year 2 | Front tyre worn close to the legal limit | Advisory | Pass |
| Year 3 | Front tyre tread depth below the legal limit | Major | Fail |
The advisory in year 2 was the cheap moment to act. By year 3 the owner pays for the tyre and, unless the tyre is changed at the same centre in the retest window or the repair is a quick item, may also pay a retest fee. An owner who reads advisories as a to-do list rarely faces the year 3 result.
What to do if your car fails
First check the failure sheet, which lists each item. If a dangerous defect is listed, do not drive the car. If your existing MOT is still valid and nothing dangerous was recorded, you can drive it away, but you should still arrange the repairs quickly. If your old MOT has expired, you can legally drive only to or from a place where repairs will be carried out, or to a pre-arranged MOT test. Next decide where the repair will be done, because that affects the retest cost: a partial retest is free if the car stays at the test centre and is retested within 10 working days. Our guide what to do after a failed MOT walks through repair, retest and appeal options in order, and MOT costs sets out the retest fees. If you believe the result is wrong, you can appeal to DVSA. For a failed vehicle the complaint form must be sent within 14 working days.
Different vehicles, different tests
This guide uses cars as its main example, but the same principles apply to other vehicles with differences in what is checked. A motorcycle test looks at a different set of items from a car test. A van falls under the car-style tests if it is light enough, and heavier vehicles are tested differently. The class of your vehicle determines the checks, as explained in MOT test classes. For records on other vehicle types see the van MOT check and the motorcycle MOT check, and for cars the car MOT check.
Use your car’s history to predict the next test
The best clue to what might fail next is what has failed or been noted before. Every test since 2005 in England, Scotland and Wales is recorded in the online MOT history, including advisories. Look up your registration in the MOT check and open the full MOT history to see whether an item such as tyre wear or a brake component has been noted repeatedly. Our guide to reading MOT history shows how to interpret what you find, and the used car checklist covers what to look for when buying.
If you are buying, the same approach tells you what the previous owner has already been warned about. A car whose advisories have vanished from the record may have been repaired, which is a good sign if there are invoices, or it may simply have been tested by a different tester who noticed different things.
What our free tools show and what they cannot
| Question | What our free tools show | What they cannot do |
|---|---|---|
| What failed on previous tests? | Every recorded test since 2005 with defects and categories | Predict what the next tester will find |
| Is my MOT valid? | Status, expiry date and days remaining | Book or cancel a test |
| Is an advisory still open? | The advisory tracker follows each item through later tests | Confirm that a repair was done to a good standard |
| Will my car pass? | Nothing. A pass depends on the car on the day | Replace a pre-test check or a garage inspection |
To find a garage to test the car, see finding an MOT test centre, and to keep track of the date, set a free MOT reminder. Newly registered cars have a different timeline, covered in the first MOT guide, and the basics of the whole system are in what is an MOT.
A pre-test check does not replace the test. It removes the cheap, obvious failures such as bulbs, wipers, a missing fuel cap or a dirty number plate, and gives you time to price the more expensive items before you are standing at a garage counter.
Common mistakes before an MOT
- Leaving a warning light on and hoping the tester will not mind.
- Judging tyre tread by eye or by a coin alone.
- Ignoring last year’s advisories.
- Arriving with a dirty or damaged number plate.
- Booking at the last minute so there is no time to repair and retest while the old MOT is valid.
- Assuming the test checks the engine, clutch and gearbox, so a car that passes is mechanically sound.
- Driving a car with a dangerous defect away from the test centre because the old MOT is still in date.
Glossary
- Advisory
- A note on a pass that a component is not yet defective but will become so.
- Dangerous defect
- A direct and immediate risk to road safety or the environment. A fail, and the vehicle must not be driven.
- Major defect
- A defect serious enough to fail the test.
- Minor defect
- A defect that is present but not serious enough to fail the test.
- PRS
- Pass after rectification at the test: a defect fixed while the car was at the test centre.
- Retest
- A further test after a fail, with fee rules that depend on where and how quickly the repair is done.
- Tread depth
- The depth of the grooves in a tyre. The legal minimum for cars is 1.6mm across the central three-quarters of the tread, around the whole tyre.
- VIN
- The vehicle identification number, unique to each vehicle.
Sources and further reading
- GOV.UK: Getting an MOT, including what is tested and the MOT test results pages
- DVSA: MOT inspection manual and the guidance on defect categories
- GOV.UK: Checking your tyres and tread depth
- GOV.UK: MOT test fee
- TfL: Ultra Low Emission Zone, and GOV.UK: Clean Air Zones
Complete MOT timeline, mileage analysis, recurring advisories and a plain-English summary in one downloadable document.
We are an independent service and not affiliated with DVLA, DVSA or GOV.UK. The rules and fees on this page can change, so confirm them on GOV.UK. See our terms and editorial policy, and the page on how we get our data. Contains public sector information licensed under the Open Government Licence v3.0.