MOT Failure Rates UK: The Most Common Reasons Cars Fail

Summary

• Almost 4 in 10 cars fail: Around 37% of MOT tests result in a failure. But most fails are easy to avoid.
• Lights are the top reason: Blown bulbs cause more fails than anything else. A quick check at home can save you time and money.
• Simple checks help: Most common fails can be spotted with a basic car maintenance checklist before you go.

Nobody wants to fail their MOT. It costs money, wastes time, and means your car might not be safe to drive.

But the truth is, most MOT failures are caused by simple problems. Things you can check yourself in 10 minutes.

Let's look at the real numbers and the most common reasons cars fail. Then we'll show you how to avoid them.

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UK MOT Failure Stats

The Driver and Vehicle Standards Agency (DVSA) keeps records of every MOT test in the UK. Here's what the numbers show:

• Around 37% of cars fail their MOT on the first attempt.
• Over 30 million MOT tests happen every year in the UK.
• More than 11 million of those result in a fail.
• Older cars fail more: Cars over 10 years old have a higher failure rate than newer ones.

That sounds scary. But here's the good news. Most of these fails are for small, cheap things.

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Top 10 Reasons Cars Fail the MOT

Here are the most common reasons for MOT failure in the UK:

Rank	Reason for Failure	% of Fails	Easy to Fix?
1	Lights and signalling	~30%	Yes - replace bulbs
2	Suspension	~13%	Needs a mechanic
3	Brakes	~10%	Sometimes DIY
4	Tyres	~8%	Yes - check tread
5	Driver's view of the road	~7%	Yes - wipers/washer
6	Exhaust and emissions	~7%	May need a mechanic
7	Steering	~5%	Needs a mechanic
8	Body and structure	~4%	Depends on damage
9	Seatbelts	~3%	Needs a mechanic
10	Windscreen	~2%	May need repair

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1. Lights and Bulbs - The Biggest Fail

Blown bulbs are the number one reason for MOT failure. Around 3 in 10 fails are because of lighting problems.

This includes headlights, brake lights, indicators, fog lights, and number plate lights.

The fix is usually simple and cheap. Most bulbs cost just a few pounds. You can often fit them yourself.

How to avoid this fail

• Get someone to stand behind your car while you press the brakes. Check both brake lights work.
• Turn on your headlights. Check dipped and full beam.
• Flick on each indicator. Walk around and check they all flash.
• Don't forget the number plate light at the back.

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2. Suspension Problems

Worn shock absorbers and damaged springs are the second biggest cause of MOT failure.

Signs of suspension problems include:

• Bouncy ride: Your car bounces more than once when you push down on a corner.
• Clunking sounds: Noises when driving over bumps.
• Uneven tyre wear: This often means your suspension is worn.
• Car leans in corners: It doesn't feel stable when turning.

Suspension repairs usually need a mechanic. But spotting the signs early means you can fix them before the test.

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3. Brakes and Tyres

Worn brakes and bald tyres are dangerous. They're also common MOT fails.

Brakes

The tester measures how well your brakes stop the car. If they're worn, they won't stop evenly.

Listen for squealing or grinding when you brake. That's a sign your pads need replacing. See our brake replacement guide for costs and advice.

Tyres

The legal minimum tread depth is 1.6mm. Use a 20p coin to check. If you can see the outer band of the coin, your tread is too low.

Also check for bulges, cuts, and cracks. These are instant fails. Learn more in our tyre replacement guide.

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4. Emissions and Exhaust

Your car must not produce too much pollution. The tester checks exhaust gases to make sure.

Diesel cars are tested for excess smoke. Petrol cars are tested for carbon monoxide levels.

Tips to pass emissions

• Drive before the test: A 20-minute drive warms the engine. Warm engines produce cleaner emissions.
• Use the right oil: Old or wrong engine oil can increase emissions.
• Fix warning lights: An engine warning light often means emissions problems.
• Check your exhaust: Holes or leaks in the exhaust pipe cause failures too.

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Which Cars Are Most Likely to Fail?

Not all cars fail at the same rate. Here are some facts:

• Older cars fail more: Cars over 12 years old have failure rates above 50%.
• Well-maintained cars pass: Regular servicing makes a big difference.
• Some brands do better: Japanese cars like Honda and Toyota tend to have lower failure rates.
• Diesels fail more on emissions: Diesel particulate filter problems are a growing cause of failure.

Before buying a used car, always check its MOT history. This shows you past advisories and failures. It's a great way to spot ongoing problems.

You can run a quick check with CarOwl's free MOT checker.

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How to Pass Your MOT First Time

Follow this quick checklist before your test:

1. Check all lights - every single one, including number plate lights.
2. Test your horn - make sure it's loud and clear.
3. Check tyre tread - use the 20p coin test on all four tyres.
4. Fill washer fluid - an empty bottle is an instant fail.
5. Test wipers - they must clear the screen without smearing.
6. Try all seatbelts - they must clip, hold, and retract.
7. Look under the car - check for leaks or hanging parts.
8. Check mirrors - make sure none are cracked or loose.
9. Drive for 20 minutes - warm the engine before the test.

Want to know exactly what happens on the day? Read our guide on what happens during an MOT test.

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Most MOT fails are avoidable. A few minutes of checking at home can save you a trip back to the garage. Keep your car well maintained, and you'll pass with flying colours.

Not sure when your MOT is due? Check your MOT due date now and book early to avoid the rush.

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