What Happens During an MOT Test: Step-by-Step Guide

Every car over three years old in the UK must pass an annual MOT test to confirm it meets minimum road safety and environmental standards. Yet for many drivers, particularly those booking their first test, the process can feel mysterious. What exactly does the tester look at? How long does it take? What happens if your car fails? This guide walks you through what happens during an MOT test from the moment you pull into the garage to the moment you drive away with your certificate.

Before the Test: What to Bring and Check

You do not need to bring any paperwork to an MOT — the tester only needs your vehicle. That said, it is worth running through a few quick checks the evening before to avoid an easy fail. Top up your screenwash, check that all lights are working, make sure your tyres have at least 1.6 mm of tread depth, and ensure your number plates are clean and secure. You should also confirm your vehicle details using a free MOT check so you know exactly when your current MOT expires and whether there are any advisory notes from the previous test to address.

Arrive a few minutes early so the tester can take your details and log the vehicle on the DVSA's online system. The tester will confirm the vehicle identification number (VIN), mileage, and registration plate before the inspection begins.

Stage 1: Visual Exterior Inspection

The what happens during an MOT test process begins with a walk-around inspection of the exterior. The tester checks:

• Number plates — correct format, secure fixing, no cracks obscuring characters
• Bodywork — no sharp edges or protrusions that could injure pedestrians
• All exterior lights — headlights, brake lights, indicators, fog lights, reversing lights
• Windscreen — no chips or cracks larger than 10 mm in the driver's swept area, or 40 mm elsewhere
• Wipers and washers — blades must clear the screen effectively
• Mirrors — at least two mirrors providing a rearward view

If the tester spots an obviously dangerous defect at this stage — a completely shattered headlamp, for example — they may record a failure immediately, though in most cases they will complete the full inspection first.

Stage 2: Under-Bonnet Checks

Next, the tester opens the bonnet and checks fluid levels and key components. This includes engine oil, brake fluid, and screenwash. They will also inspect the brake servo and master cylinder for leaks, check battery security, and confirm the VIN stamped on the vehicle matches the registration documents. Hydraulic or electronic power steering fluid may be checked depending on the vehicle's system.

This stage takes only a few minutes but can catch issues that drivers overlook during day-to-day ownership.

Stage 3: Interior and Safety Equipment Checks

The tester then sits inside the vehicle to verify the following:

• Horn — must work and be audible
• Seats and seatbelts — belts must latch, retract, and show no fraying; seats must be securely fixed
• Steering — checked for excessive play or stiffness
• Dashboard warning lights — critical lights such as ABS, airbag, and electronic stability control (ESC) must extinguish after the engine starts
• Speedometer — must be present and operational
• Fuel cap — must seal correctly to prevent vapour escape

Stage 4: Brake and Suspension Testing on the Ramp

The vehicle is driven onto a two-post ramp or inspection pit. This is the most detailed phase, covering the areas most likely to cause a failure. The tester checks:

• Tyres — tread depth, sidewall condition, correct fitment, matching sizes on the same axle
• Suspension components — wishbones, control arms, shock absorbers, spring condition
• Steering linkage — track rod ends, ball joints, rack gaiters
• Brakes — brake lines, callipers, discs, and pads are inspected visually for wear and corrosion
• Exhaust — checked for leaks, security, and excessive noise
• Fuel system — pipes and connections inspected for leaks
• Underside corrosion — excessive rust on structural members is a failure point

For deeper background on which issues most frequently cause failures, see our guide to common MOT failures.

Stage 5: Brake Performance Test

Brakes are tested on a rolling road brake tester — a set of rollers built into the workshop floor. Each wheel is placed on the rollers in turn, and the tester applies the brakes while the rollers spin. The machine measures braking force at each wheel independently. The results must meet DVSA minimum efficiency thresholds: typically 50% for the service brake and 16% for the handbrake. An imbalance between the left and right wheels on the same axle can also trigger a failure, even if the overall efficiency is sufficient.

Stage 6: Emissions Test

The emissions test varies depending on whether your car is petrol, diesel, or electric. For petrol vehicles, a probe is inserted into the exhaust and the tester measures carbon monoxide (CO), hydrocarbons (HC), and lambda (oxygen balance). Diesel vehicles undergo a smoke opacity test, where the engine is revved hard and the density of the exhaust smoke is measured. Electric vehicles do not require an emissions test but must still pass all other relevant checks. Failing the emissions test is one of the most common reasons for an MOT failure on older vehicles.

After the Test: Pass, Fail, or Advisory

Once all checks are complete, the tester submits the results electronically to the DVSA. You will receive a printed VT20 pass certificate or a VT30 refusal notice if the vehicle has failed. If there are items that are not quite at failure level but could worsen over time, these are recorded as advisories — you are not required to fix them immediately, but it is sensible to address them before your next test.

Your MOT result is automatically recorded on the DVSA database, which means you can check it online at any time. If you want to review your car's full MOT history, including all previous pass and fail records, you can do so for free. Looking at past advisories is an excellent way to identify recurring problems before your next test.

Understanding what happens during an MOT test removes the anxiety from the process. Carry out the basic pre-test checks, use your previous MOT history to fix outstanding advisories, and you give your car the best possible chance of sailing through first time.