What happens if you ignore an MOT advisory

First, the honest answer: usually nothing happens

An advisory is not a requirement and not a defect. Your car passed. Nobody will fine you, your insurance is unaffected, and in most cases the item on the certificate will still be sitting there, unchanged, at your next test. The interesting question is not whether you must act — it is which of them are quietly expensive to leave.

That question has never had a numerical answer in the UK, because answering it needs two things at once: the national test record, to see what each advisory did next, and repair pricing, to see what it cost when it did. Everyone with the first lacks the second. We publish both, so this page multiplies them. If you want the plain-English version of what the words on your certificate mean, that is in our guide to MOT advisories — this page is about consequences, not vocabulary.

Which advisories actually come back

Suspension advisories return as an MOT failure 18.7% of the time and fluid-leak advisories 1.3%, according to PriceMyRepair’s analysis of 145.1 million DVSA advisories. Every advisory in the record was followed forward to the same vehicle’s later tests. Three things could happen: it was fixed, it was still there and still an advisory, or it came back as a failure. The last column is the one that costs money.

Percentages are rounded to one decimal place as published. Rows do not sum to 100% because a minority of advisories belong to vehicles with no subsequent test in the record — scrapped, exported or off the road. Steering advisories are excluded from this table: the category rate is published on our advisory decoder, but the sample size behind it is not, and we do not publish a rate without the sample it rests on.

The category people ignore most is the one that matters least

Fluid leaks are the most-ignored MOT advisory category in Britain and the least likely to return as a failure, in PriceMyRepair’s analysis of DVSA data. Look at the ignored column, then at the failure column. Fluid leaks are ignored more than anything else on the certificate — 43.5%, the highest figure in the record. They are also the least likely thing to come back: 1.3%, the lowest figure in the record. On the single most-ignored advisory in Britain, the crowd is accidentally right.

Suspension is where the same instinct goes wrong. It is ignored at almost the same rate — 37.1% — and comes back as a failure fourteen times more often. A corroded coil spring or a worn arm bush does not leak, does not smell and does not make a noise you can hear over the radio. It reads as the mildest line on the certificate and behaves as the most expensive.

Structural corrosion is the reverse case, and worth naming. It has the second-lowest failure rate at 6.7% — but only because it has by far the highest repair rate, 75.9%. People do not gamble on rust near a mounting point, and that is why it rarely returns. Its low number is evidence of caution, not of safety. It is the one line here where a low percentage should not reassure you.

What ignoring each one is actually worth

The most expensive MOT advisory to ignore is a misting shock absorber, at £48 of carried cost, and the cheapest a number plate lamp at £3 — a sixteenfold spread, according to PriceMyRepair’s analysis. A failure rate on its own tells you half the story, because coming back as a failure matters more when the repair is £320 than when it is £17. Multiplying the two gives the number that ranks them honestly — the cost you are carrying by leaving that line on the certificate.

Last column = category failure rate × midpoint of the repair range, rounded to the nearest pound. Worked example, the top row: 18.7% × £255 = £47.69, shown as £48. It is not a bill you will receive — it is the average cost of leaving that line alone, across every car that leaves it alone. Repair ranges are independent-garage prices from our own cost guides. Corrosion near a mounting is deliberately absent: no honest repair range exists for it, because the bill depends entirely on what is found once the underseal comes off.

Why the median gap is always about 376 days

In PriceMyRepair’s analysis of DVSA data, every advisory category converges on roughly the same median gap — about 376 days — before it returns as a failure, and that is the finding. Suspension 376 days, tyres 376, bearings 378, lamps 379, exhaust 379, oil 379, structure 384. Springs, bulbs and bearings have nothing mechanical in common and wear out on completely different timescales — yet they all fail, on average, one year and eleven days after being flagged.

That is because the number is not measuring the part. It is measuring the owner. A car is only inspected once a year, so an advisory that is never acted on can only be re-classified as a failure at the next test. The median is a year because the test is annual, not because components politely wait twelve months to break.

Which reframes the whole decision. The gap is not a countdown you can watch — the part might go at month three or hold for five years. What the data says is narrower and more useful: if you leave it, the moment you find out is almost always the next MOT, at whichever garage happens to have your car, with the certificate already printed. Deciding at the time of the advisory is the only point where you are choosing rather than reacting.

What to do with your own list

Three groups, and the sorting takes about a minute once you know which category each line belongs to.

Tyres sit outside this framework and should not be judged on the failure rate at all. An advisory tyre is legal today, but tread near 1.6mm is a stopping-distance question long before it is a test question — and unlike everything else here, it is enforceable on the road. Detail on our tyre advisory page.

How these numbers were produced

Ignoring an MOT advisory — FAQ

Is it illegal to ignore an MOT advisory?

No. An advisory is a note, not a defect — your car passed, the certificate is valid and there is no obligation to act. The only exception is where the underlying condition becomes an offence in its own right, such as a tyre going below 1.6mm of tread after being flagged as close to it.

What percentage of MOT advisories become failures?

It depends entirely on the category, which is the point of this page. Suspension advisories return as a failure 18.7% of the time, lamps 14.4%, body and exhaust 11.8%, tyres 9.9%, brakes 9.4%, structure 6.7%, axles and bearings 6.5%, and fluid leaks just 1.3% — a fourteenfold spread across lines that look identical on the certificate.

Which MOT advisory is the most expensive to ignore?

A shock absorber with light misting of oil, at £48. That is its 18.7% return rate multiplied by the £255 midpoint of a £150–£360 repair. A corroded coil spring is next at £42 and a worn suspension arm bush at £39 — the whole top of the ranking is suspension, because it combines the highest return rate with mid-range repair costs.

Which advisory is safe to leave?

On test outcomes alone, an oil leak described as not excessive — it returns as a failure 1.3% of the time, one car in 77, and works out at £6 of carried cost. That is only a statement about MOT risk, though. A seep can still matter mechanically, and the low figure means it will rarely be forced on you, not that it is harmless.

How long do I have before an advisory becomes a failure?

The median is 376 days, and that number is about the test schedule rather than the part. Because a car is only examined once a year, an unrepaired advisory can usually only be reclassified at the next MOT. Individual components may fail within weeks or last for years — the median simply reflects when people find out.

Does an advisory affect my insurance or the value of my car?

It has no direct effect on a policy, since the car holds a valid MOT. It does affect resale: MOT history is public, and a buyer who checks will see every advisory ever issued and whether it was still there at the following test. A repeated, unactioned advisory reads as deferred maintenance.

Why do so many people ignore oil leak advisories?

Fluid leaks are the most-ignored category in the record at 43.5%, probably because a seep is invisible from the driving seat and the repair sounds expensive. As it happens, that instinct matches the data — it is also the category least likely to return as a failure. It is the one place where the crowd’s inattention lands on the right answer.

Why does corrosion have a low failure rate if rust is serious?

Because it has the highest repair rate of anything measured — 75.9% of structural corrosion advisories are dealt with, against 44.2% for suspension. It rarely returns as a failure because people rarely leave it. Its low percentage is evidence of how seriously owners take it, not evidence that it is minor.

Should I fix advisories at the same time as the MOT?

Where the work overlaps, usually yes — the car is already on a ramp and the wheels may already be off, so labour is not paid twice. That is most valuable for suspension items, which sit at the top of both the return-rate and the cost-of-ignoring rankings. Our service and MOT guide covers how garages price the combined visit.

How do I know which category my advisory belongs to?

The certificate wording maps to a DVSA defect section, and the section determines the rate — for example 5.3 for suspension, 1.1 for brakes, 5.2 for tyres. Rather than decode it yourself, our advisory decoder reads your MOT history from your registration and tells you the category, the return rate and the price for your model.

Every advisory, decoded

The categories above are national. These pages take one line from the certificate at a time and say what a tester saw, what it costs and how urgent it is.

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