What actually fails the MOT

Lamps, reflectors and electrical equipment are the most common MOT failure category in Great Britain, recorded in 10.89% of all tests and 25.01% of all defects (DVSA 2024/25, cars and light vans). Tyres appear in only 6.39% of tests but account for 60.12% of every defect graded dangerous. The initial failure rate, before any repair and retest, was 28.08%. These are national rates, not the odds for any one car.

The most common failure is not the most dangerous failure

This is the distinction the published statistics make and most write-ups collapse. DVSA records two different things about every defect: which category it belongs to, and how serious it is. Rank the categories by how often they appear and you get one order. Rank them by how often they are graded dangerous and you get an almost opposite one.

Both statements are true at once, and neither is a ranking of “what to worry about” on its own. A blown bulb is the single most likely thing to be written on a test result. A tyre is the single most likely thing to be written on it that DVSA considers an immediate risk. Those are different questions, and a page that answers only the first one leaves the reader looking at the wrong part of the car.

Failure categories by how often they appear

DVSA, Great Britain, 2024/25, table DVSA/MOT/03, classes 3 and 4 — cars and light vans up to 3,000kg. “Share of tests” is DVSA’s count of the tests in which that category produced at least one failure item, as a percentage of all tests of those classes; a minor defect, which passes, is not counted in it. “Share of defects” is that category’s slice of every failure item recorded across all categories. The two have different denominators and should not be compared with one another.

Both columns are quoted from the same DVSA table. The five rows above are the five largest; DVSA gives a share of defects to every category it publishes and they total 100%, so these five hold 81.36% of every failure item recorded and the categories not listed hold the rest.

These shares total more than the 28.08% initial failure rate, and that is not an error. One test can be recorded against several categories, and DVSA recorded an average of 2.44 defects per initial failure. A car that fails usually fails on more than one thing.

The word “initial” matters. An initial failure is the result of the first test in a sequence, before any repair and retest, so 28.08% is not the share of cars left permanently without a certificate: a car that failed, was repaired and passed the retest is counted inside it.

Where the ordering changes: dangerous defects

At least one dangerous defect was recorded in 7.70% of tests. Restrict the count to those defects alone and the table above rearranges itself.

• Tyres move from fourth to first. They appear less often than lamps, suspension or brakes, yet they hold 60.12% of the dangerous grade.
• Suspension moves the other way. It is the second most common category at 8.73% of tests but accounts for 5.34% of dangerous defects.
• Lamps do not appear in the top three at all. The category that dominates the frequency table is largely a category of minor and major defects rather than dangerous ones.

What these numbers are, and what they are not

Every figure above is a rate across a population of tests, and a population rate does not transfer to an individual.

Minor, major, dangerous: a minor defect still passes

Defects found at an MOT are graded, not just listed. The grade decides the result, and one of the three grades does not fail the car at all.

An advisory is not a failure either. An advisory is the tester saying something will need attention before long — a tyre approaching the limit, corrosion starting somewhere that is not yet structural. It carries no grade and it does not affect the result. It is a note about the future, written down and dated.

The practical consequence is that “it passed” and “nothing was found” are not the same claim. A pass certificate can carry minor defects and advisories at the same time. If a seller says a car sailed through, the certificate itself is the thing to read, not the summary. Our explanation of what an MOT advisory means goes through what an advisory does and does not commit anybody to.

What this means before you buy

A single MOT result tells you about one day. The history tells you about the car, and it is free to read from the registration alone. What is worth looking for is not the pass or fail line but the pattern underneath it.

• Repeat advisories in the same category. An advisory that appears in one year and again the next has not been acted on. That is a cost that has not been spent yet, and it is sitting in front of whoever buys the car.
• Tyres and suspension first. Tyres because they hold 60.12% of the dangerous grade nationally; suspension because it is the second most common category at 8.73% of tests.
• Corrosion advisories. These get worse rather than better. Read the sequence, not the latest line.
• A pass with a long list. Several minor defects and advisories on a pass is a different car from a clean pass, even though both read as “passed”.
• Mileage between tests. Recorded at every test, so the history doubles as a dated mileage record. A jump or a stall that does not match the seller’s account is worth asking about.

Great Britain and Northern Ireland

Every statistic above is DVSA data for Great Britain. Roadworthiness testing in Northern Ireland is a separate system run by DVA.

The history difference is the one that matters most to a buyer. In England, Scotland and Wales the public record reaches back to 2005, which is long enough to see a pattern of advisories across most of a car’s life. In Northern Ireland it starts at 2017, so on an older car a large part of the record simply is not published, and its absence says nothing about the car. The Great Britain figure is the one GOV.UK states carries no VAT, and it is the only one of the three that has stood unchanged since 2010. The DVA fees are set prices at DVA’s own centres rather than caps, and they were raised from £30.50 and £18.50 after DVA’s 2023 fee consultation.

Age exemption from testing is a Great Britain rule, on a different test again from the historic vehicle tax class — the Northern Ireland exemptions are DVA’s own and are not described here. Whether a car is exempt is covered in is my car exempt from the MOT, and the tax side in our guide to vehicle tax when you buy a used car.

Where these figures come from

• Failure rates, category shares and dangerous-defect shares: DVSA MOT testing data for Great Britain, tables DVSA/MOT/01 and DVSA/MOT/03, financial year 2024 to 2025, classes 3 and 4 — cars and light vans up to 3,000kg. Initial failure rate 28.08%; at least one dangerous defect in 7.70% of tests; 2.44 defects per initial failure on average; 35,229,047 tests across all classes. The annual totals for 2024/25 were published on 30 October 2025.
• What kind of statistic this is: DVSA states of this data set that “it is not classed as an ‘official statistic’”, which means it is not subject to scrutiny and assessment by the UK Statistics Authority. It is administrative data from DVSA’s own testing records. Vans over 3,000kg and up to 3,500kg are class 7 rather than class 4, are counted in a separate table, and are not described by any figure on this page.
• Defect grading: DVSA grades every defect minor, major or dangerous. A minor defect is compatible with a pass; major and dangerous are failures.
• Fees and first-test ages: DVSA for Great Britain, DVA for Northern Ireland. The Great Britain class 4 figure is a statutory maximum a garage may charge less than, and GOV.UK states no VAT is charged on it. The DVA figures are the fees DVA charges at its own test centres — set prices rather than maximums, raised from £30.50 and £18.50 after its 2023 fee consultation.
• MOT history: published from 2005 in England, Scotland and Wales, and from 2017 in Northern Ireland. Free to check from the registration at gov.uk/check-mot-history.

This page describes national statistics and the rules of the test. It is not an assessment of any particular vehicle: for that, read the car’s own MOT history and have it inspected.