What is Checked in an MOT?

An MOT test is a crucial annual check to ensure your vehicle is safe to drive and meets the UK's road safety and environmental standards. This guide will walk you through every single check our expert technicians perform during your MOT, helping you understand the process and prepare your vehicle for the best possible chance of passing.

Why is an MOT so important?

An MOT isn't just a legal requirement; it's a vital safety check for you, your passengers, and other road users. Once your vehicle is over three years old, you're legally obligated to have it tested every 12 months.

Beyond safety, there are other serious reasons to keep your MOT up-to-date:

• It's Illegal to Drive Without One: Driving a vehicle without a valid MOT certificate is against the law. Police and mobile camera units can remotely check your vehicle's MOT status.

• Avoid Fines and Points: Being caught without a valid certificate can result in a hefty £2,500 fine and three penalty points on your driving licence.

Road Tax: You will be unable to renew your road tax without a current MOT certificate.

 MOT Checks Explained: What’s Checked, How It’s Checked, and Why

1) Vehicle identification and basics

How it’s checked

The tester visually inspects the VIN (vehicle identification number) and number plates for presence, legibility and security. The speedometer is checked for fitment and, where applicable, nighttime illumination.

What the tester looks for

• VIN is permanently marked and clearly readable.

• Number plates in the correct format, securely fixed and legible; no cracked or delaminated plates that obscure characters.

• A present, readable speedometer (and illumination where relevant).

Why it matters

Accurate identification helps protect against vehicle crime and ensures that your car can be quickly traced in emergencies or collisions. Police ANPR systems use number plates to check tax, insurance and MOT validity, so illegible or insecure plates can result in fines or your vehicle being pulled over. A working speedometer is not just a legal requirement; it helps you maintain safe speeds and avoid penalty points for unintentional speeding.

2) Lamps and electrical equipment

How it’s checked

All required lamps (headlamps, indicators, stop lamps, tail lamps, rear fog, number-plate lamps and DRLs where fitted) are switched on in sequence. Headlamp aim is measured with a calibrated aligner. The battery and visible wiring are inspected for security and condition.

What the tester looks for

• Correct operation, colour and brightness.

• Secure lamp units; intact lenses; no water ingress affecting output.

• Accurate headlamp aim and beam pattern (to avoid dazzling others).

• Battery is securely mounted and not leaking; wiring is free from damage or chafing.

Why it matters

Lighting faults are among the most common MOT failures. Poor headlamp aim or missing bulbs reduce your ability to see hazards and increase the risk of dazzling others, especially at night or in poor weather. 

Sound wiring and a secure battery also prevent electrical shorts that could lead to breakdowns or even fires. In short, functioning lights protect you and everyone around you.

3) Brakes

How it’s checked

Overall brake performance and left–right balance are measured on a roller brake tester. If the system isn’t suitable for rollers (certain 4x4s), a decelerometer road test may be used. 

The hydraulic system, pipes and hoses are examined for condition and leaks. The parking brake is tested for travel and holding ability. Where fitted, ABS/ESC warning lamps are observed.

What the tester looks for

• Service and parking brake efficiency above minimum thresholds; imbalance within permitted limits.

• No fluid leaks; pipes not corroded or damaged; flexible hoses not perished or bulging.

• Acceptable pedal feel and reserve travel; parking brake holds the vehicle securely.

Why it matters

Brakes are the most critical safety system on any car. If they are inefficient, unbalanced or leaking fluid, your stopping distance will increase dramatically, especially in wet conditions.

Even a slight imbalance can cause your car to pull to one side under braking, putting you at risk of losing control or colliding with other vehicles. By ensuring the braking system works effectively, the MOT helps prevent accidents caused by avoidable brake failure.

4) Steering and suspension

How it’s checked

With the car on turn plates or a lift, the tester turns the wheel from lock to lock and physically checks steering joints, linkages and mountings for security and play. Power steering (including electric systems) is assessed for leaks, noises and correct assist. Suspension components (springs, dampers, arms and bushes) are inspected with the wheels both loaded and, where needed, lifted.

What the tester looks for

• Excessive free play, worn ball joints, split gaiters, loose or damaged mountings.

• Power-steering leaks or malfunctions.

• Broken springs, leaking or severely worn dampers, split bushes, cracked arms.

Why it matters

Your steering and suspension systems keep your car stable and predictable on the road. If there is excessive play in the joints or wear in the bushes, your steering may feel vague or unresponsive. 

Worn dampers or broken springs affect how well tyres grip the road surface, particularly when cornering or braking. Failures here can lead to a dangerous loss of control, especially at high speeds or during emergency manoeuvres.

5) Tyres and wheels

How it’s checked

Tyres are inspected around the full circumference for condition, size and type. Tread depth is measured across the central three-quarters of the tread. The tester checks load/speed ratings where required, wheel condition, and wheel security. The TPMS warning lamp (if fitted and testable) is observed.

What the tester looks for

• Tread depth of at least 1.6 mm across the central three-quarters of the tread around the full circumference.

• No cuts, bulges, sidewall damage or exposed cords; matched sizes and compatible types on the same axle.

• TPMS not indicating a malfunction on vehicles where it’s part of the test.

Why it matters 

Tyres are the only contact point between your car and the road. With insufficient tread depth, they lose the ability to disperse water, massively increasing the risk of aquaplaning in wet conditions. 

Structural damage, bulges or exposed cords can cause sudden blowouts, which are highly dangerous on motorways. Ensuring tyres are roadworthy means your vehicle has the grip it needs to brake safely, steer accurately and maintain stability.

6) Visibility: windscreen, wipers, washers and mirrors (or cameras)

How it’s checked

The tester examines the swept area of the windscreen and the driver’s field of vision through the front side windows. The wash/wipe is operated to confirm that it clears effectively. Mirrors (or approved camera systems where fitted) are checked for security and adequate rearward view.

What the tester looks for

• Damage or tinting that significantly affects the driver’s view, especially in “Zone A”, a central strip in the swept area.

• Wipers that clear the screen properly and washers that supply sufficient fluid.

• Secure mirrors or camera systems providing an adequate rearward view.

Why it matters

Clear vision is fundamental to safe driving. Even a small chip or crack in the swept area of the windscreen can distort your view or grow into a larger fracture. 

Poorly performing wipers or empty washer bottles leave you blinded in the rain or when dirt and spray hit the screen. Working mirrors or camera systems are equally important, allowing you to judge overtaking and manoeuvres without putting others at risk.

7) Seatbelts, seats and SRS (airbags)

How it’s checked

All seatbelts are pulled and latched to confirm condition, operation and locking. Mountings and seat security are checked. The SRS/airbag warning lamp is observed through the ignition cycle; a persistent fault indication is recorded as a defect where testable.

What the tester looks for

• Frayed, cut or damaged belts; faulty buckles; missing or insecure mountings.

• Front seats that won’t lock securely upright; loose runners.

• Airbag or restraint system warning lamp is illuminating due to a fault.

Why it matters

Seatbelts and airbags are your last line of defence in a crash. If a seatbelt doesn’t lock correctly or is frayed and weakened, it may fail when you need it most. Loose seats could shift under impact, preventing the restraint system from working correctly. 

An illuminated airbag warning light often means the system won’t deploy in an accident – a potentially life-threatening fault. MOT checks ensure these critical protections are functioning.

8) Body, structure and closures (doors, bonnet, boot)

How it’s checked

The tester inspects the vehicle structure, including sills, chassis rails and other load-bearing members, for corrosion, damage or poor repairs, especially within prescribed distances of key mountings (brakes, steering, suspension, seatbelts). Doors, bonnet and boot/tailgate are opened and closed to confirm they latch and release correctly.

What the tester looks for

• Excessive corrosion, fractures or insecure repairs that weaken the structure or affect the attachment of safety-critical components (particularly within “prescribed areas”).

• Sharp edges are likely to injure pedestrians or cyclists.

• Front doors that open from inside and outside; a bonnet and boot that latch securely.

Why it matters

The body shell is part of the car’s safety cage. Corrosion around suspension mounts, seatbelt anchor points, or chassis rails can significantly weaken crash protection and impact how the car handles loads. Poorly repaired accident damage may leave sharp edges that can injure pedestrians or cyclists. 

Doors that don’t open properly could trap occupants in an emergency, while a bonnet or boot that flies open at speed is a severe hazard. This section of the test ensures your car remains structurally safe.

9) Exhaust, emissions and fuel system

How it’s checked

The fuel system is examined for leaks and a secure, sealing cap. The exhaust is checked for security, leaks and effective silencing. 

Emissions are tested to the standards applicable to your vehicle’s age and fuel type: petrol cars typically undergo a gas analysis (CO, HC and Lambda), while diesels receive a smoke opacity test using a calibrated meter. Excessive visible smoke or an illuminated engine warning related to emissions can lead to failure, depending on age and system.

What the tester looks for

• No fuel leaks; cap present and sealing properly.

• Exhaust present, secure and not leaking in a way that affects performance or noise.

• Emissions within the legal limits for the vehicle; no excessive visible smoke on diesels.

Why it matters

Fuel leaks are a clear fire hazard. An insecure or leaking exhaust increases noise, allows fumes into the cabin and can reduce the effectiveness of catalytic converters or DPFs. High emissions or visible smoke are both environmental problems and a sign of poor engine health, which can result in expensive repairs later. The MOT keeps harmful pollutants within legal limits and ensures your vehicle runs cleanly and safely.

10) Horn

How it’s checked

The horn is pressed to confirm that it sounds and is suitable for road use.

What the tester looks for

• A working horn with a continuous, appropriate tone (novelty tunes aren’t acceptable).

• An accessible control that functions reliably.

Why it matters 

It may seem trivial, but a working horn is an essential warning tool. In unexpected situations, sounding your horn can prevent a collision by alerting other drivers, cyclists or pedestrians to your presence. A faulty or novelty horn that isn’t suitable for road use removes this important layer of safety.

Will I be issued with MOT Certificate?

When your vehicle passes its MOT test, you will be issued with a new-style MOT certificate number which consists of an A4 sized piece of paper with the certificate printed on it. You should keep the MOT certificate somewhere safe.

What isn’t covered by an MOT?

Although the MOT is thorough in checking safety and environmental standards, it does not assess the engine, clutch or gearbox for wear and tear. 

These components are vital to how your car performs, but aren’t included in an MOT because they don’t directly fall under roadworthiness legislation. That means your car can technically pass its MOT even if it’s running poorly, hesitating under load or struggling to change gears smoothly.

This is where routine servicing comes in. A car service looks at the overall mechanical health of your vehicle, covering aspects like oil condition, fluid levels, filters, spark plugs, and gearbox operation.

If you’ve noticed symptoms such as reduced fuel economy, unusual noises, smoke, or difficulty engaging gears, a service appointment alongside your MOT is the most effective way to catch underlying problems before they develop into costly repairs. While the MOT ensures your vehicle meets the legal minimum for road use, a service helps extend its lifespan and keep it running reliably day-to-day.

For most drivers, combining an MOT with a car service is a practical choice. It saves time by reducing multiple visits to the garage, but more importantly, it gives you peace of mind that your car isn’t just legally compliant but mechanically sound too. 

Addressing wear in the engine, clutch or gearbox before it leads to breakdown also helps retain resale value and ensures smoother, more efficient driving. Ultimately, servicing complements the MOT by filling in the gaps it doesn’t cover — keeping you safe, compliant and protected from unexpected failures.

Summary

For more information on every aspect of MOTs, we’ve created a [complete comprehensive MOT Guide]. It covers a wide range of topics, including what an MOT is, how to book your test, what happens if your car fails, and the key laws surrounding MOT requirements. It’s the ideal resource if you want to understand the process in detail and prepare with confidence before test day.