MOT advisories explained: what they mean and when to worry

Published 13 September 2026 · 4 min read · Reviewed against official sources

Your car passed its MOT, and the certificate came with a list of advisories. Most people file it and forget it. That is a mistake in one direction and an unnecessary worry in the other, because advisories range from "a bulb is slightly dim" to "the rear subframe is rusting through and will fail next year". Knowing which is which is the difference between a cheap fix now and an expensive one later.

The three categories, and what they mean

Since 2018 the MOT has classified defects into three tiers:

  • Dangerous. An immediate risk to safety or the environment. The car fails, and it is illegal to drive it away — even to a garage — until the defect is fixed.
  • Major. A fault that could affect safety, other road users, or the environment. The car fails. It can be driven to a place of repair if the existing MOT is still valid, but not otherwise.
  • Minor. A fault with no significant effect on safety or the environment. The car passes, and the item is recorded as an advisory — along with anything else the tester chooses to note as worth monitoring.

So an advisory is, by definition, something the tester judged not yet serious enough to fail. The word "yet" is doing a lot of work in that sentence.

Why testers record advisories

Partly for you: it is genuinely useful to know a tyre has 2.5mm of tread left. Partly for themselves: a tester who notes deteriorating corrosion and passes the car has documented their judgement, and if the component fails six months later the record shows it was flagged. And partly because the DVSA expects it — a test with no advisories on a ten-year-old car would raise more eyebrows than one with four.

Advisories to act on soon

These are the ones that either become a fail at the next test, or become a safety problem before it:

  • Tyres close to the limit. The legal minimum is 1.6mm. An advisory at 2mm means you have a few thousand miles at most, less in winter. Replace before the tread reaches 3mm if you can — wet braking distances lengthen sharply below that.
  • Brake pads or discs wearing. "Brake pad(s) wearing thin" means the next test is a fail unless they are changed, and braking performance degrades before that.
  • Corrosion — anywhere structural. Subframes, sills, chassis legs, suspension mounting points, brake pipes. Corrosion does not improve. Get it inspected and quoted; a small welding repair now prevents a large one later, and past a certain point a car is uneconomic to repair.
  • Oil or fluid leaks. A "slight" leak is a seal on its way out. Watch the level, and budget for the repair.
  • Suspension bushes and ball joints with play. These fail when play becomes excessive. They affect handling and tyre wear in the meantime.

Advisories that can usually wait

  • Non-structural corrosion — on a wheel arch or a door bottom. Cosmetic, though it will spread.
  • Slight wear on wiper blades, minor stone chips to lights, a slightly noisy exhaust mounting.
  • Under-tray or trim loose or missing. Not a safety item.
  • Registration plate slightly deteriorated. Only becomes a fail when it is illegible.

Reading the wording

Testers use standardised phrasing, and the qualifiers carry meaning. "Slight" or "not excessive" is the mild end. "Excessive" would have been a fail. "Corrosion to the [component], not yet affecting strength" is a component the tester expects to fail in future. "Deteriorated" on a rubber part means it is perishing. If you see the same component described with escalating qualifiers across consecutive tests — slight, then noticeable, then a fail — you are watching a fault develop in real time, and the cheapest point to intervene was the first mention.

How advisories become fails

There is no rule that says an advisory must fail next time. It becomes a fail when it crosses the threshold in the inspection manual: tread below 1.6mm, play in a joint beyond the tolerance, corrosion within a set distance of a mounting point that has weakened the metal. That can take one year or five. What the advisory tells you is that the component is on the path, and roughly where on the path it is.

Can you challenge an advisory?

You can ask the tester to explain or reconsider it at the time, and a second garage can give an opinion. You cannot formally appeal an advisory in the way you can appeal a fail, because the car passed. In practice, if an advisory seems wrong, a second inspection is the answer; if the second garage disagrees, they will not repeat the advisory at the next test and the record moves on.

Using advisories when selling

Buyers who know what they are doing read the MOT history first, and repeated advisories are the thing they look for. A car with three years of the same corrosion advisory sells for less and slower than one where each advisory was addressed. If you plan to sell in the next year or two, dealing with advisories as they arise is not just maintenance — it is the difference between a straightforward sale and a series of awkward conversations.

Sources

Related guides

MOT & motoringHow to read an MOT history before buying a used carThe MOT history is the only free, official, tamper-proof record of a used car's life. Here's what to look for — mileage that doesn't add up, advisories that keep coming back, and the gaps that tell you a car sat unused or uninsured.MOT & motoringWhat happens if your MOT expires: the law, your insurance, and the one exceptionDriving without an MOT is a fine, points in some cases, and — the part people underestimate — an insurance policy that may not pay out. The rules, the single lawful exception, the 40-year exemption, and how to avoid it happening again.RatesHow to challenge your Northern Ireland rates valuationThink your capital value is too high? Here's the difference between a review and an appeal, the 28-day rule that decides which you can use, the grounds that actually succeed, and how to check comparable homes first.