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

A track rod end with slight play fails on the same joint at the next test 18.6% of the time and brake fluid close to the minimum mark 0.3%, according to PriceMyRepair’s analysis of 166.2 million DVSA advisories followed to the same vehicle’s next test. Two things could happen: the same wording was written again, or the part failed. The first column is the one that costs money.

The twelve wordings most likely to fail next time, of 65 measured. “Fails on the same part” means a major or dangerous defect under the same code, naming the same component, at the next test 180 to 730 days later. Every wording links to its own page with the full breakdown.

The advisories people ignore most are not the ones that matter least

The most-ignored line on a British certificate is the number plate, in PriceMyRepair’s analysis of DVSA data. 40.1% of cars with a deteriorated registration plate are given the same advisory again a year later, for a fix that costs a few pounds. A corroded subframe is re-advised 39.8% of the time and a noisy exhaust 39.7%. Cheap, dear and chosen sit side by side at the top of the ignored list.

Across all 65 wordings, the link between how often a line is ignored and how often it fails is weak. The correlation is r = -0.13. People do leave the harmless ones more often, but not by much, and the thing they are sorting on is not risk. It is whether the fault can be seen, heard or felt from the driving seat.

That is why joints with play sit where they do. A track rod end or a suspension arm ball joint with slight play is silent, changes nothing about how the car drives, and reads as the mildest line on the certificate. It fails next time one car in six. A seeping oil leak is visible on the drive, smells, and fails one car in 83.

What ignoring each one is actually worth

The most expensive MOT advisory to ignore is suspension arm ball joint has slight play, at £34 of carried cost, 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 £280 than when it is £25. Multiplying the two gives the number that ranks them honestly — the cost you are carrying by leaving that line on the certificate.

Last column = that wording’s failure rate × midpoint of the repair range, rounded to the nearest pound. Worked example, the top row: 16.0% × £210 = £33.67, shown as £34. 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. Only wordings with a direct repair price are shown; where the fix depends on what is found (a rusty subframe, a corroded arm, a seeping rack) no honest range exists and the wording is left out. Repair ranges are independent-garage prices from our own cost guides.

Why nobody can tell you how long you have

The test record cannot answer “how long until it fails”, and neither can anyone using it. A car is inspected once a year, so an advisory that is never acted on can only be reclassified as a failure at the next test. Measure the gap between an advisory and the failure that follows it and the answer is a year, for every wording, because that is how far apart the tests are. It is a fact about the calendar, not about springs, bulbs or bearings.

What the record can answer is the odds. Of the cars that carried this exact wording into their next test, this share failed on that part. That is the number on every page in this cluster, and it is the one worth acting on: the part might go at month three or hold for five years, but the moment you find out is almost always the next MOT, at whichever garage happens to have the car, with the certificate already printed.

Which reframes the whole decision. Deciding at the time of the advisory is the only point where you are choosing rather than reacting. After that, the calendar chooses for you.

What to do with your own list

Three groups, and the sorting takes about a minute once you have looked up each line.

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 on the exact wording, which is the point of this page. According to DVSA MOT data analysed by PriceMyRepair, a track rod end with slight play fails on the same joint at the next test 18.6% of the time, a suspension arm ball joint 16.0%, a worn suspension arm bush 7.4%, an oil leak that is not excessive 1.2%, and brake fluid close to the minimum mark 0.3% — a spread of more than sixty times across lines that all read as minor.

Which MOT advisory is the most expensive to ignore?

Suspension arm ball joint has slight play, at £34. That is its 16.0% chance of failing on the same joint next time multiplied by the £210 midpoint of a £140–£280 repair. Service brake binding but not excessively is next at £26 and shock absorbers has a slightly worn bush at £23.

Which advisory is safe to leave?

On test outcomes alone, undertray not fully secure and brake fluid close to the minimum mark: each returns as a failure on that item well under one time in a hundred, and works out at less than a pound of carried cost. That is only a statement about MOT risk. Low fluid is usually worn pads, and the low figure means the test will rarely force it on you, not that it is harmless.

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

The data cannot say, and any site that gives you a number of days is measuring the test calendar rather than the part. A car is examined once a year, so an unrepaired advisory can only be reclassified at the next MOT: the gap is a year for every wording, whatever the component does in between. What the record does give is the chance that the next test finds it failed, and that is what this page ranks.

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.

Which advisories do people ignore most?

A deteriorated registration plate is written down again at the next test 40.1% of the time, a corroded subframe 39.8%, a noisy exhaust 39.7% and corroded brake pipes 44.4%. Across the 65 wordings we measured, the link between how often a line is ignored and how often it fails is weak, at r = -0.13: people leave what they cannot see or hear, not what is cheap or safe.

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 and steering joints, which sit at the top of both the failure and the cost-of-ignoring rankings. Our service and MOT guide covers how garages price the combined visit.

Why is the figure for my advisory lower than the category figure I have seen elsewhere?

Because a category figure counts any advisory in a group followed by any failure in that group: a worn bush advisory followed by a broken spring counts. This page counts only a failure on the same component after the same wording, which is what a single line on your certificate is actually predicting. For most wordings the difference is two to three times.

How do I know the figure for my own advisory?

Every wording on this page links to its own page, with the failure rate, the tester notes, the age curve and the models most affected. Or paste your certificate into our advisory decoder, which reads each line and gives the figure and the price for your model.

Every advisory, decoded

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.

Related guides