How to Prepare for Your MOT: 20 Checks That Could Save You Money

Around 40% of cars fail their MOT the first time. That is a lot of unnecessary stress, extra garage visits, and repair bills that could have been avoided. Many MOT failures are for simple, fixable issues that any car owner can check at home in 15 minutes. DVSA data shows that lighting faults, tyre issues, and brake problems account for the vast majority of failures. Most of these are easy to spot and cheap to fix before you take the car in.

This is not about gaming the system. It is about catching obvious problems early, fixing them on your terms (rather than at the garage's inflated rates), and avoiding the hassle of a retest. Here are 20 checks you can do yourself, starting with the most common MOT failure reasons.

According to DVSA data, the top five reasons for MOT failure are: 1. Lighting and signalling (around 18% of all failures). Blown bulbs, cracked lenses, incorrectly aimed headlights. 2. Suspension (around 13%). Worn shock absorbers, damaged springs, perished bushes. 3. Brakes (around 10%). Worn pads and discs, seized calipers, corroded brake lines. 4. Tyres (around 8%). Insufficient tread, damage, incorrect size. 5. Driver's view of the road (around 7%). Damaged windscreens, worn wipers, obstructed views. These five categories account for more than half of all MOT failures. Most can be checked at home without any tools. You can see how your specific car model performs on our reliability rankings page.

1. Headlights (dipped and main beam) Turn on your headlights and walk around the car. Both dipped beams and both main beams should work. If one is dimmer than the other or has a yellowish tint, the bulb is likely on its way out. Replace it now. Most headlight bulbs cost £5 to £15 and can be changed in under 10 minutes. 2. Brake lights Ask someone to press the brake pedal while you check from behind. Both brake lights and the high-level brake light (if fitted) must work. A blown brake light bulb is one of the most common MOT failures and costs under £5 to fix. 3. Indicators Activate each indicator in turn and check all four corners plus the side repeaters. A fast-flashing indicator usually means a bulb has blown somewhere in that circuit. If your car has LED indicators, a single failed LED within the cluster can cause a failure. 4. Rear fog light and reversing light At least one rear fog light must work. Reversing lights are not tested on the MOT, but it is worth checking them anyway. Fog light bulbs rarely blow, but the switch or wiring can develop faults, particularly on older cars. 5. Number plate lights These are easy to forget. The rear number plate must be illuminated by at least one working bulb. Check it at night or in a dark garage. The bulb is usually a small festoon type costing about £2.

6. Tread depth The legal minimum is 1.6mm across the central three-quarters of the tyre, around its entire circumference. Use a 20p coin: insert it into the tread groove, and if you can see the outer band of the coin, the tread is below 1.6mm. Check all four tyres and the spare (if you have one). Driving on illegal tyres carries a £2,500 fine and 3 penalty points per tyre. 7. Tyre condition Look for cuts, bulges, cracks, or objects embedded in the tyre. Bulges on the sidewall are particularly dangerous and will cause an instant MOT failure. Run your hand along the inner edge of each tyre (where you cannot easily see) to feel for uneven wear, which might indicate an alignment or suspension problem. 8. Tyre size and type All tyres on the same axle must be the same size and type. You cannot mix radials and cross-plies on the same axle. Mismatched tyres are a common reason for unexpected MOT failures, especially if the car has had a puncture repair where a different tyre was fitted. 9. Wheel condition Badly buckled or cracked wheels will fail the MOT. This is more common with alloy wheels, which can crack if they hit a pothole. Spin each wheel and look for visible damage to the rim.

10. Brake pads and discs You can usually see the brake pads through the wheel spokes. The friction material should be at least 3mm thick. If you can see the metal backing plate, they need replacing. Check the brake discs for deep scoring or a pronounced lip at the edge, both of which indicate they are worn and may need replacing. 11. Brake fluid level Open the bonnet and find the brake fluid reservoir (usually a small, translucent plastic container near the back of the engine bay). The fluid level should be between the MIN and MAX marks. Low fluid is often a sign of worn brake pads, as the pistons extend further to compensate, drawing more fluid into the calipers. 12. Handbrake The handbrake should hold the car on a slope without needing to be pulled excessively high. If you have to pull it more than halfway up its travel, it may need adjusting. The Ford Focus and Vauxhall Corsa are both known for handbrake cable stretch, which is a simple and cheap adjustment.

13. Windscreen damage The MOT allows a maximum chip or crack of 10mm in the driver's "swept area" (the area cleared by the wipers directly in front of the steering wheel). Outside this critical zone, the limit is 40mm. A small chip can often be repaired for free through your insurance. A crack that exceeds the limits will need a full windscreen replacement. 14. Wipers Worn wiper blades that leave streaks or miss areas of the windscreen will cause a failure. New blades cost £10 to £20 for a pair and take two minutes to fit. Check that the rear wiper works too if your car has one. 15. Washers Your windscreen washers must produce a jet of fluid that adequately cleans the windscreen. Top up the washer fluid, and check that the nozzles are not blocked (a pin can clear them). It seems trivial, but empty washer fluid is a legitimate MOT failure.

16. Engine oil level While the MOT does not specifically test oil level, a low oil level can cause the engine management light to illuminate, which will cause a failure. Check the dipstick and top up if needed. 17. Emissions warning light If your engine management light (the amber engine symbol on the dashboard) is illuminated, the car will fail the MOT. This is a relatively recent change that catches many drivers out. Get the fault codes read (most garages will do this for £20 to £30) and fix the issue before the test. Common causes include faulty oxygen sensors, catalytic converter issues, and loose fuel caps. 18. Exhaust Start the car and listen for blowing or rattling from the exhaust. Walk behind and check for excessive smoke: blue smoke indicates oil burning, black smoke suggests a fuelling problem, and white smoke (beyond initial warm-up condensation) can indicate a head gasket issue. Any of these can cause an emissions failure. The Volkswagen Golf TDI and BMW 3 Series diesel are both models where emissions issues are relatively common in older examples.

19. Mirrors You need at least two functioning mirrors, and one must be the driver's door mirror. Cracked or missing mirrors will fail the MOT. Replacement glass for most models costs £10 to £30 and clips into the existing housing. 20. Bodywork and corrosion Structural corrosion within 30cm of a load-bearing component (suspension mount, subframe, seatbelt anchor) will fail the MOT. Surface rust on panels is generally fine, but look underneath the car (particularly the sills, wheel arches, and subframe) for anything that looks like it is rusting through. Older Ford Fiestas and Vauxhall Corsas are known for rear wheel arch corrosion.

Give the car a basic clean, inside and out. A dirty car does not fail the MOT, but a tester who cannot see a component (because it is caked in mud) may record it as a failure. Make sure the boot is empty so the tester can access the seatbelt mounts. Remove any air fresheners or stickers from the windscreen that might obstruct the driver's view. If you discover any issues during these checks, you have two options: fix them yourself (lights, wipers, and washers are easy DIY jobs) or take the car to a garage for repair before the MOT. Either way, you will save money compared to discovering the problem during the test, when you will pay for the retest and potentially inflated repair prices. To see how your specific car compares to the model average, enter the reg plate into our free car checker. You will see its complete MOT history, every advisory ever noted, and a health score based on its track record. For a comprehensive check including stolen, finance, and write-off status, use our full history check. Want to know which cars are most likely to pass? Browse our reliability rankings or check running costs by model to see how maintenance costs vary across different makes.