A clean MOT pass can still hide a £900 bill. Here's where to look.
Everyone checks pass or fail. Almost nobody reads the advisories — and that's exactly where the cost of a used car is written down in advance.
A mate of mine bought a used hatchback last year. "Full MOT history, passed every time," the seller said, and the paperwork backed it up — a green PASS every single year going back ages. Three months later he was £900 down: two tyres, a set of brake discs, and welding to deal with corrosion that had been quietly spreading underneath.
Here's the thing: none of that was a surprise hiding in the car. It was all sitting in the MOT history in plain sight. He just didn't know which bit to read.
Everyone reads the wrong line
When most people check a car's MOT history, they look at one word: pass or fail. Passed every year? Great, clean car, job done.
But a pass only means the car met the MOT standard on the day. It tells you nothing about what's wearing out, what the tester was worried about, or what's about to become your problem. That information lives in the part nobody reads: the advisories.
An advisory is the tester saying, "This isn't bad enough to fail you today, but keep an eye on it." Corrosion starting to form. A tyre close to the legal limit. Brakes wearing thin. An oil leak that's "slight" — for now. The car still passes. The advisory just gets noted and forgotten.
And that's exactly why it's so useful to a buyer. The advisories are a roadmap of what the car is going to cost you next.
The same advisory, ignored two years running, becomes a failure — and your bill — in the third. Any single test looks fine. The trail across tests is the bit that talks.
The patterns that actually cost you money
Reading advisories across several years is where the value is. Three patterns are worth knowing:
The same advisory, year after year. If "corrosion to rear subframe" or "engine oil leak" shows up three MOTs running, that's not a one-off note — it's a problem the previous owner kept paying to ignore until they sold it. Corrosion in particular only goes one way. Caught early it's a wire-brush job; left for years it's welding, and welding to pass an MOT can easily run into several hundred pounds.
An advisory that's getting worse. Watch for something that starts as an advisory and climbs toward a major defect. "Tyre worn close to legal limit" this year means you're buying a car that needs new tyres very soon — roughly £250–£400 for a set on most cars. "Brake disc worn" heading toward "brake disc worn, pitted or scored" is often around a £150–£300 job waiting for you. The history is telling you the bill before you've even handed over the cash.
A suspiciously clean recent sheet. Years of advisories, then a sudden spotless MOT at a testing station the car's never used before, right before it goes up for sale? That's often a pre-sale tidy-up — just enough done to get a clean pass and a better asking price. Not always dodgy, but always worth a second look and a question to the seller.
Probably fine
A few advisories that don't recur. Anything flagged in an earlier year has clearly been dealt with and doesn't reappear. The history reads like a car that's been looked after as it ages.
Negotiate or walk
The same advisory repeats year after year, or worsens into a major. Corrosion that keeps spreading. A stack of "wearing" notes all landing at once — that's a cluster of bills about to become yours.
How to actually read it
The MOT history is free to check on the GOV.UK service — type in the reg and it's all there. The catch is that it's a wall of text, one block per year, with the advisories buried in amongst the pass and fail lines. To spot a three-year corrosion trend you've got to read every year and hold it all in your head, which is exactly why most people skim the passes and miss the story.
That's the bit we built Car Timeline to do. You put in the reg and, instead of a wall of text, you get the full history laid out in order with the recurring advisories and the worsening patterns flagged — plus a plain-English verdict on whether the history looks clean or whether there are patterns worth checking before you buy. Two minutes, before you spend thousands.
Let Car Timeline read the advisories for you
Add a UK registration and Car Timeline reads the available MOT history, surfacing the advisories that recur or worsen so you're not scanning years of tests by eye for the bill the history is predicting.
Before you buy anything
Whether you use the free GOV.UK page or let us do the reading for you, do one thing before you buy a used car: read the advisories, not just the passes. A pass tells you the car met the standard on one day a year ago. The advisories tell you what it's going to do to your bank account next.
The cheapest car is rarely the one with the lowest price. It's the one without a £900 surprise three months in.
Common questions
What are MOT advisories?
An MOT advisory is a note the tester records about an item that is starting to wear or has a minor issue, but isn't yet bad enough to fail the test. The car still passes. Advisories are a warning that something may need attention soon — a tyre approaching the legal tread limit, light corrosion, or brakes beginning to wear.
Should I worry about buying a car with advisories?
A single advisory is usually nothing to worry about and is normal on an older car. What matters is the pattern across several years. The same advisory appearing test after test suggests a problem the owner ignored, and an advisory that worsens into a major defect points to a repair bill you'll inherit. Read the whole history, not one line.
What's the difference between an advisory, a minor, a major and a dangerous defect?
Advisory and minor items don't fail the MOT — they're noted so you keep an eye on them. Major and dangerous defects do fail the test and must be repaired, with a dangerous defect meaning the car shouldn't be driven until it's fixed. An item flagged as an advisory one year can escalate to a major failure later if it's left unrepaired.
Where can I check a car's MOT advisory history?
The full MOT history, including advisories at each test, is free on the GOV.UK MOT history service by entering the registration number. It's shown as a block of text per year, so spotting a recurring or worsening advisory across several tests takes some reading. Car Timeline lays the same history out in order and flags the advisories that recur or worsen.