MOT History Red Flags:What Every Trader Should Check Before Bidding

Two minutes on gov.uk can save you thousands. The MOT history is the most underused tool in a car trader's kit. It's free, it's public, and it tells you things about a car that no seller description, no photo set, and no auction condition report will ever reveal.

This guide covers exactly what to look for, which advisory codes matter, and the patterns that separate a clean car from a money pit.

How to Check MOT History

Go to gov.uk/check-mot-history. Enter the registration number. That's it. No account needed, no fee, no limit on checks.

You'll see every MOT test since digital records began in 2005. Each test shows the date, mileage, result (pass or fail), and every advisory and failure reason. This is data straight from the DVSA testing centres, so it's reliable.

Mileage: The First Thing to Check

Every MOT records the odometer reading. This gives you a year-by-year mileage trail that's extremely hard to fake (you'd have to tamper with the odometer before every single test).

What a Healthy Record Looks Like

Steady, consistent increases. A typical UK car covers 6,000-12,000 miles per year. Slight variation is normal (people's driving habits change, they move house, change jobs). What you want to see is a broadly consistent upward trend.

Warning Signs

• Mileage drops between tests. The odometer reads 85,000 one year and 72,000 the next. This is physically impossible and is a strong indicator the car has been clocked. Walk away immediately.
• Suspiciously low annual mileage after years of high mileage. If a car was doing 15,000 miles a year for five years and then suddenly drops to 3,000, the odometer may have been rolled back between tests and then driven normally after.
• Gaps in the MOT record. A car that disappears from the MOT record for two or three years and then reappears at a lower mileage has almost certainly been tampered with. The gap is there because the owner didn't want an MOT on record at the higher mileage.
• Very high annual mileage. Not a scam indicator, but a cost indicator. A car doing 25,000+ miles a year will have more wear on every component. Price your bid accordingly.

Mileage clocking hasn't gone away. According to RAC and HPI data, an estimated 1 in 16 used cars in the UK has a mileage discrepancy. The MOT history is your best defence.

Advisories: The Real Story

Advisories are issues that the MOT tester noted but that weren't serious enough to fail the test. They're split into categories, and understanding these categories is the difference between bidding with confidence and bidding blind.

MOT Red Flags: Advisories That Cost Serious Money

• "Corrosion on structural member" or "corrosion on chassis" — this is the big one. Structural rust is expensive to repair properly (if it's repairable at all). On a sub-£5,000 car, structural corrosion is borderline write-off territory. If this advisory has appeared and worsened over multiple tests, the car is rotting. Walk away.
• "Catalytic converter below efficiency threshold" — a new catalytic converter costs £400-1,200 depending on the model. If this has appeared as an advisory, it's likely to fail at the next test. Budget for it or skip the car.
• "Engine management light on" — could be anything from a £30 sensor to a £3,000 turbo failure. Without diagnostics, you're gambling. If you can't plug in an OBD scanner before buying, treat this as a major risk.
• "Airbag warning light on" or "SRS warning light" — airbag repairs are expensive and safety-critical. A dashboard warning light for the airbag system typically means a faulty sensor, wiring issue, or a deployed airbag that wasn't properly replaced. Costs range from £200 for a sensor to £1,000+ for module replacement.

Advisories That Look Bad but Rarely Matter

• "Brake disc worn but not below minimum" — this is normal wear. Budget £150-300 for new discs and pads as part of your prep, but it's not a reason to walk away. Every car with 40,000+ miles will have some brake wear.
• "Tyre worn close to legal limit" — £50-120 per tyre. Factor it into your bid. This is prep cost, not a defect.
• "Oil leak, not excessive" — common on older engines and usually manageable. A minor weep from a rocker cover gasket is a £50 fix. A major leak from a sump or rear main seal is different. Context matters.
• "Slight play in steering rack" — on high-mileage cars, some play is normal. If it's been noted as "slight" and hasn't worsened over multiple tests, it's usually fine. If it's progressing from "slight" to "excessive," budget £300-600 for replacement.

Advisories That Should Change Your Bid

• Suspension components worn. Drop arms, anti-roll bar links, bushes, shock absorbers. Not catastrophic individually (£100-300 each), but if three or four suspension components are flagged in the same test, you're looking at £500-1,000 in suspension work. Reduce your bid accordingly.
• Exhaust system corrosion. If the exhaust has been flagged for corrosion in consecutive tests, it's going to need replacing soon. Budget £200-500 for a full exhaust system on a mainstream car.
• Windscreen damage. A chip in the driver's line of sight is an MOT fail item. A chip outside it is an advisory. Either way, budget £60-80 for a repair or £200-400 for a replacement.

Failure History: What It Tells You

A car that has failed an MOT isn't automatically a bad buy. What matters is why it failed and what was done about it.

Acceptable Failures

A single failure for a light bulb, a wiper blade, or a tyre is nothing to worry about. These are consumable items that wear out. The car was retested and passed, meaning the issue was fixed.

Concerning Failures

• Repeated failures for the same issue. If a car has failed for "brake performance below minimum" two years running, the owner is doing the minimum to pass and not addressing the underlying problem.
• Structural failures. "Prescribed area of vehicle structure is excessively corroded" is a fail. If a car has failed for structural corrosion and was retested as a pass, it was repaired, but welded patches on structural members aren't a long-term fix on a budget car. The rust will come back.
• Emissions failures. Particularly on diesels. An emissions failure often means the DPF, catalytic converter, or EGR valve needs attention. These are expensive parts with complex diagnostics.

The Retest Gap

When a car fails and is retested, check how long the gap was. A retest within a few days suggests a quick fix (good sign). A retest after several weeks or months suggests the repair was more complex or the owner was putting it off (less good).

Patterns to Watch Over Multiple Tests

The real power of MOT history isn't any single test. It's the pattern across 3-5 years of tests.

The Well-Maintained Car

Consistent mileage increases. Few advisories, and those that appear are resolved by the next test. No failures, or occasional failures for consumables. This car has been looked after. Your prep costs will be low.

The Deferred Maintenance Car

The same advisories appearing year after year, getting progressively worse. "Brake discs worn" for three consecutive years. "Suspension arm corroded" that started as "slight" and is now "moderate." The owner has been kicking the can down the road, and you'll be the one paying for the accumulated neglect.

The Freshly Patched Car

A long history of failures and advisories, then a recent test that's suspiciously clean. This can mean the car was properly refurbished (good), or that the owner did the bare minimum to get it through the test before selling (bad). Cross-reference with the mileage and price. If a car with 120,000 miles and a history of advisories suddenly passes clean, be cautious.

How ScanAuctions Uses MOT Data

When you run a scan on ScanAuctions, every car gets its MOT history pulled automatically. The platform flags specific risk indicators:

• Mileage discrepancies between MOT records
• Outstanding advisories that are likely to need attention
• High advisory counts relative to the car's age
• Failure patterns that suggest deferred maintenance

Each car gets a risk score alongside its profit margin and deal verdict. A car that looks profitable on paper but has a string of structural advisories gets flagged before you waste time researching it further.

The Chrome extension shows the same MOT summary when you're browsing listings on AutoTrader, Motorway, or CarWow. Advisory count, last test result, and key flags are visible without leaving the listing page.

Checking MOT history should be automatic for every car you consider buying. It takes two minutes manually. With ScanAuctions, it's already done for you.

If you're new to car trading, our complete car flipping UK guide covers the full process from finding stock to selling it. For a breakdown of which auction sites to check, see best car auction sites for UK dealers.

Get started and see risk flags on every car in your next scan.