An upcoming MOT can raise questions for any car owner, especially when you want a clear understanding of what the test involves and how to avoid unnecessary failures. This guide explains the entire MOT process so you know exactly what happens during the inspection and why each check matters. It covers what is checked in an MOT, the faults that can lead to a failure, what happens if your car does not pass, and what advisories mean for future maintenance.
What is an MOT and when do you need one
An MOT (Ministry of Transport) test is a yearly inspection required in the UK to confirm a car is safe and roadworthy. It becomes due once your car is three years old (from its date of first registration), then every year after that.
After passing, you receive a certificate showing the test date and expiry date. You can have your car re-tested up to one month (minus a day) before expiry and still keep the original renewal date.
Note: an MOT is not a full service. It does not assess engine health, clutch condition, gearbox, or the mechanical condition of the car’s running gear.
Driving a vehicle without a valid MOT (or with one that has expired) is illegal, unless the car is being driven only to a pre-booked MOT test. There is no 14-day grace period.
What do they check in an MOT?
During the MOT, a qualified tester inspects all major components that affect safety, emissions, or road legality.
Here is a breakdown of the main areas checked in an MOT and what is examined:
Body, Structure and General Condition
The car’s body and chassis are checked for excessive corrosion, damage, and sharp edges that might cause injury. Any serious rust or structural weakness, especially in safety-critical areas (like near suspension or steering mountings), can cause a fail.
If your car has a towbar (or other attachments), these are checked for security, proper wiring (13-pin socket), and acceptable condition.
Brakes, Brake Warning Lights and Brake Fluid
The braking system is thoroughly tested. This includes checking condition and operation of service brakes, parking brake, brake pads/discs condition (where visible), and ensuring the car stops evenly and safely.
If fitted, the anti-lock braking system (ABS), electronic stability control (ESC) or electronic parking brake is also checked. Their dashboard warning lights (malfunction indicator lamps) must not be illuminated. Brake fluid is also reviewed to ensure it is not contaminated or at risk of leaking.
Tyres, Wheels and Tyre Pressure Monitoring System (TPMS)
All tyres (except spare) are checked for correct size and type, security, overall condition (no bulges, cuts, or damage), and adequate tread depth. The legal minimum tread is 1.6 mm across the central three-quarters of the tyre.
For vehicles first registered on or after 1 January 2012, if they have a tyre-pressure monitoring system (TPMS), the TPMS warning light must work (or else the test fails).
Lights, Electrical Equipment and Registration Plates
All required exterior lights must work correctly and be the right colour. This includes headlights (dip and main beam), indicators (including hazard), brake lights, side lights, rear lights, fog lights (if fitted), number-plate lights, and reflectors (on vehicles built after 1980). Headlamp aim is checked so they do not dazzle oncoming drivers.
Registration plates must be securely fitted, in the correct format and colour, and fully legible from a distance.
Windscreen, Wipers, Washers, Mirrors and Driver’s View
The windscreen is checked for damage or obstruction, especially in the driver’s line of sight. Large chips or cracks can cause a fail. Wipers and washers must work correctly to keep the screen clear. Mirrors must be securely fitted, sufficient in number (drivers side, internal or passenger side external), and in good condition.
Doors, Boot, Bonnet, Seats and Seatbelts
All doors must open and close properly, and front doors must open from inside. The boot (or tailgate) and bonnet must latch securely. Seats must be firmly attached, with seat backs locking in the upright position. For driver’s seat, the adjustment mechanism (if fitted) must work. Seatbelts (including pretensioners and load limiters if fitted) must be present, undamaged, secure, and fully operational.
Steering and Suspension
Steering components and suspension (springs, shock-absorbers, joints) are checked for excessive wear, damage or corrosion. The steering wheel and column must be secure. If the car has power steering, fluid levels may be checked.
Exhaust, Emissions, Fuel System and General Under-Carriage
The exhaust system must be secure and complete (including catalytic converter if originally fitted), with no leaks or excessive noise. Emissions are tested to ensure the car meets legal environmental standards. For diesel vehicles, a smoke test may be applied (when safe). The fuel system is checked for leaks; fuel pipes/hoses must be secure and the fuel cap must seal properly.
Horn and Warning-Device Systems
The horn must work and be loud enough for other road users to hear. Any dashboard warning lights (for airbags, seatbelt systems, ABS, ESC, TPMS etc.) are checked - if illuminated during the test (and the vehicle has those systems), that can be a failure.
Vehicle Identification Number (VIN) and Speedometer
The VIN must be present and readable (for most vehicles). For some classes of vehicle, the speedometer and odometer may also be checked.
What a car can fail on (common MOT failure reasons)
Cars often fail MOTs for relatively simple issues. Common failure causes include:
Faulty bulbs or lights
Worn tyres
Worn or damaged suspension components
Faulty brakes
Windscreen chips or cracks that affect driver visibility
Broken seatbelts or insecure seats
Emissions or exhaust faults
Structural corrosion
Because lights, tyres and suspension are so commonly problematic, a large share of MOT failures come from those areas.
What happens if your car fails its MOT
If the tester finds defects that are “major” or “dangerous,” your car will fail the MOT and you receive a “Refusal of an MOT Test Certificate”. You cannot legally drive the vehicle until the defects are fixed.
If the faults are “minor” (advisories) only, the car still passes. The advisory does not legally require repair before driving, but it flags issues the tester believes could worsen before your next MOT.
Most garages offer a free or reduced-cost retest if you return within a set timeframe (commonly 10 working days) after fixing the problems.
If your MOT certificate is still valid, and the failure is non-dangerous, you may legally drive the car away to a repair shop. But if the failure lists dangerous faults (brake failure, fuel leak, structural integrity), you must not drive the vehicle.
Understanding MOT Warnings and Advisories
During an MOT, not all faults result in a failure. Some defects, while not serious enough to fail the test, are recorded as “advisories” (sometimes called “minor defects”). These include things like slightly worn tyres still above legal tread depth, small chips in a windscreen outside the driver’s main view, or bulbs that are weakened but still functioning.
Advisories are a heads-up. They show parts that could deteriorate before next year’s MOT. It makes sense to address them promptly, which reduces the chance of a failure next time.
MOT testers classify issues into three categories: Minor (Advisory), Major, Dangerous. Minor issues do not cause a fail (but are noted). Major defects cause a fail. Dangerous defects cause a fail and make the car illegal to drive.
How to prepare ahead so you have the best chance of passing
You don’t need special tools to do a quick pre-MOT check. Simple checks can often catch issues before the test.
Walk all around the car and switch on every light (headlights, tail lights, brake lights, indicators, fog lights, number plate lights). Replace any blown bulbs and clean dirty lenses.
Inspect tyres for correct tread depth (at least 1.6 mm across central ¾), no cuts or bulges, and correct size. Check tyre pressure (especially if your car has TPMS).
Examine windscreen for cracks or chips; focus especially on the area in front of the driver. Check wipers and washers work, and top up washer fluid if needed.
Test horn to make sure it works and is loud.
Make sure number plates are clean, legible, and correctly formatted.
Check that seatbelts are present, retract correctly, fasten properly, and show no fraying or damage.
Ensure all doors, the boot, and bonnet open and close securely and latch properly.
Remove unnecessary clutter from inside like hanging items, heavy loads, or loose objects that might obstruct driving or access to controls.
If you have a towbar, make sure it and any electrical socket is intact and clean.
Clear warning lights from the dashboard (ABS, airbags, TPMS etc). If any lights are illuminated when you start the engine, arrange a check-up before the MOT.
Why MOT matters
An MOT ensures your car meets minimum safety and environmental standards to drive on UK roads. It gives you, and the authorities, confidence the vehicle is not a danger to you or other drivers.
However, it does not replace regular servicing. The MOT does not check mechanical health of the engine, gearbox, clutch, or many other wear-and-tear items. You should still follow the manufacturer’s service schedule.
Because the MOT only checks visible and testable items, you should regularly maintain and inspect your car, not rely on the annual MOT alone.
If this is your first MOT, treat it as a chance to run through a simple checklist and catch easy-to-fix issues before the test. Many common failures come from simple problems, such as blown bulbs, worn tyres, dusty number plates, or chipped windscreens. A quick pre-check can make the difference between a pass and a fail.
Remember: an MOT checks safety and emissions, not your engine’s performance or how well the car drives. Keep your car maintained and serviced between MOTs to avoid surprises. If your car is due it’s MOT do not delay, find a reputable MOT test centre like Plympton Car Centre.
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