The most common MOT defects, word for word (not just the category)
Broken down to the exact wording, not broad DVSA categories, and restricted to defects that actually failed the car, not advisories. From 54 million real tests.
MOT DATA · 5 min read
Categories hide the real story
DVSA's own published failure breakdown groups everything into broad categories: lights and electrics, suspension, tyres, brakes and so on. That is useful for a quick view but it hides which single defect is actually doing the damage inside each category. We joined the DVSA's separate defect-level (reason-for-rejection) extract against 54,086,786 first-time car MOT tests from 2024, the same join behind the failure list on every model page on this site, and instead of grouping by category we ranked every one of the 527 distinct defect descriptions that actually failed a car on its own.
Why 527 and not every defect DVSA records
DVSA testers do not just record a fail. Each defect citation carries its own severity code: Advisory (noted, does not affect the result), Minor (recorded, does not fail the car on its own), rectified on the spot during the test, or Fail (actually caused the test to fail). Pooled together, those four cover 88,311,928 resolved citations across 2024, and Advisory alone is the largest single group. Only 24,791,197 of them, 28.1 percent, are the Fail type - the number below is built from those, and only those, so "most common MOT defect" here means a defect a car actually failed on, not one a tester merely noted for next time.
The single most common specific defect
It is not tyre tread. "A suspension pin, bush or joint excessively worn" is flagged as an actual fail more than any other single defect description in the country: 1,995,317 times across the 54,086,786 tests analysed, 3.69 percent of tests. "Tyre tread depth not in accordance with the requirements" is second (1,249,535, 2.31 percent) and "a tyre seriously damaged" third (1,088,821, 2.01 percent).
The rest of the top ten, word for word
In order after those three: the aim of a headlamp is not within limits laid down in the requirements (952,430); a spring or spring component fractured or seriously weakened (891,118); a lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning (881,968); a brake lining or pad worn below 1.5mm (832,151); a wiper blade missing or obviously not clearing the windscreen (742,943); a suspension joint dust cover missing or no longer prevents the ingress of dirt etc (727,753); and windscreen washers not working or not providing sufficient fluid to clear the windscreen (667,518). Suspension, tyres and lighting take seven of the top ten places once you restrict to genuine fails and stop grouping by category.
A caveat worth being upfront about
These are defect-flag counts divided by the number of tests, not a "percentage of cars with at least one problem" figure. A single test can have the same defect flagged more than once, for example two or more tyres below the tread limit on the same car, so a defect that commonly affects more than one tyre, wheel or corner at once will show a higher rate here than the share of cars affected. Treat these as "how often this exact defect actually fails a test, per 100 tests", which is also exactly how the per-model failure lists elsewhere on this site are defined, not as a claim that one in five cars on the road has illegal tyres.
Why the category numbers and these do not match
You will notice the category-level figures elsewhere on this site (tyres at 6.23 percent of cars, for instance, from DVSA's own published category summary) do not equal the 2.31 percent above for tread depth alone. That is not a contradiction: the category figure covers every tyre defect a car can fail on, of which tread depth is one, while the number above is one specific defect description on its own, using the fails-only definition described above. We are showing our workings rather than picking whichever number reads better.
How many of these are marked dangerous, not just a fail
DVSA testers do not just fail a defect, they can also mark it "dangerous": their own judgement that the car should not be driven away until it is fixed, distinct from an ordinary major or minor fail. Nobody publishes this split below national level. This figure uses the full 88,311,928 resolved citations, advisories and minors included, not just the 24,791,197 fails behind the ranking above, because a dangerous mark is about the defect DVSA saw, not only the ones that ended the test: 4,387,939 of those citations carry it, 4.97%. That share is not even across models: on the model pages elsewhere on this site, among models with a large enough sample to state it, it ranges from under 2% to over 15%, so the same defect is treated as a genuinely urgent problem far more often on some models than others.
What is this useful for?
If you are buying a cheap MOT-failure car, the failure sheet tells you exactly which of these defect descriptions apply, not just which category. Worn suspension bushes, tread depth and tyre damage are the three most likely single items on any failure sheet in the country, and all three are quick to check yourself before you bid: suspension bushes by looking for cracked or perished rubber at the pivot points, tread with a 20p coin, and tyre sidewalls by eye. Run the car through the Analyzer once you have priced the visible damage, and check the model's own failure list on its Salvage Prophet page for what is unusual about that specific model rather than the national picture.
What is the single most common specific MOT defect in the UK?
A suspension pin, bush or joint excessively worn, flagged as an actual fail 1,995,317 times across 54,086,786 first-time car MOT tests in 2024, Salvage Prophet's own analysis of the DVSA's defect-level extract, restricted to citations that caused the test to fail rather than advisories. Tyre tread depth is second at 1,249,535.