Is rust an MOT failure?

Not by itself. Ordinary dents, scrapes and faded paint are never defects, and corrosion only fails under this heading where a panel is damaged or corroded enough to be likely to cause injury when grazed, or is insecure. A panel likely to become detached is dangerous. A rotten but non-structural panel can therefore fail on its sharp edges alone.

What counts as a sharp edge at an MOT?

An edge or projection on a body panel, bumper, undertray, spoiler or mirror housing that could cut somebody who brushes against the car. Rust that has thinned metal until it leaves a hard, cut-like edge along an arch or a sill is the usual example. The test here is about injury and security rather than appearance.

Is a damaged or loose bumper an MOT failure?

It is if the bumper is insecure, or damaged so as to be likely to cause injury on contact, since both are major defects, and one likely to become detached is dangerous. Cosmetic cracks and scuffs are not defects, so a scraped but properly fixed bumper passes. Refitting one with the correct clips is £40 to £90.

Can I grind a sharp rusty edge off to pass the MOT?

Dressing the edge back with an angle grinder deals with the injury risk, so it can clear the failure. Be clear about what you have done, though: the rust is still spreading behind the paint, and filler over a rotten arch looks fine for a summer and comes back. Check for fuel lines, brake pipes and wiring behind the panel before you start.

How much does it cost to repair a rusty wheel arch?

Letting new metal into a rotten arch or sill is body-shop work at £200 to £500 per corner, mostly labour, and paint takes it to the top of the band once colour matching, blending and metallic finishes are involved. A secondhand panel from a breaker in the right colour is often the cheapest route on an older car. If the rot reaches a mounting point it becomes structural welding.

MOT defect file

Body has a sharp edge likely to cause injury

Last updated 27 July 2026

Quick answer

A panel, bumper or trim is damaged, rotted or hanging loose enough to cut somebody who brushes against it. The test is about injury and security rather than appearance, so a dent on its own is not a defect.

Typical cost: £80–£600
DIY viability: Possible with care

What you might notice

A jagged edge you can feel along a wheel arch, a sill or the bottom of a door
Flaking rust that leaves a hole with hard, cut-like edges rather than a soft crumbly one
A bumper, spoiler or trim panel hanging loose, tapping in the wind, or held on with tape
A wheel arch liner or undertray dragging, which is often what has damaged the panel behind it

What causes it

Corrosion eating through an arch or sill until the remaining metal is thin and sharp
Accident damage left unrepaired, or a panel refitted without the clips and brackets that hold its edge
Broken bumper mounts and stretched fixing tabs, which let a corner sag and stand proud
Poorly finished modifications — a cut arch, an added spoiler or a rough repair with an exposed edge

Advisory or failure?

This part of the test is about injury and security rather than appearance, so ordinary dents, scrapes and faded paint are not defects. A body panel or body component that is damaged or corroded and likely to cause injury when grazed or contacted, or that is insecure, is a major defect, and one likely to become detached is dangerous. Bumpers are assessed the same way: insecure or damaged so as to be likely to cause injury on contact is a major defect, likely to become detached is dangerous. The inspection covers all body panels, undertrays, spoilers and mirror housings. A body modification judged unsafe — meaning likely to cause injury — is a major defect, and one likely to adversely affect braking or steering is dangerous. Note the separation from the structural rules: rot in a load-bearing member is only failed under the structural heading where the rigidity of the vehicle is significantly reduced, and corrosion within a prescribed area around a mounting is dealt with under its own section. A rotten but non-structural panel can therefore fail on its edges alone.

Can you fix it yourself?

Possible with care

Refitting a loose bumper with the correct clips and brackets is straightforward, and so is replacing a broken arch liner — plastic fixings cost pennies and most of the job is finding all of them. Cutting back and dressing a sharp corroded edge is achievable with an angle grinder, but be clear about what you have done: removing the edge deals with the injury risk and does nothing about the rust, which is still spreading behind the paint. If the metal is thin enough to be sharp, the honest repair is to cut out the rot and let in new steel, and filler over a rusted arch will look fine for a summer and come back. Wear eye and hand protection, and check what is behind a panel before you grind — fuel lines, brake pipes and wiring all run closer to the sills than people expect.

What it costs

At the bottom end this is fixings and labour: refitting a bumper properly with new clips is £40 to £90, and an arch liner £50 to £120 fitted. Dressing back and treating an edge is an hour of labour. Letting new metal into a rotten arch or sill is body-shop work at £200 to £500 per corner, mostly labour, and reaches the top of the band once paint is involved — colour matching, blending into the adjacent panel and metallic or pearl finishes all add cost. A secondhand replacement panel from a breaker in the right colour is often the cheapest route on an older car. Where the rot turns out to reach a mounting point, the job leaves this band and belongs with the structural corrosion figures instead.

What happens if you ignore it

The immediate risk is somebody being cut by a car that is simply parked — a child walking past a rotten arch, or your own hand loading the boot. A loose panel or bumper at speed becomes debris on the road, and if it comes off in traffic the liability is yours. Rust does not stop of its own accord and it works outwards from behind the paint, so an arch edge left this year is an arch and inner wing next year, and once it reaches a mounting point or a load-bearing member the repair becomes structural welding at several times the price.

Common questions

Is rust an MOT failure?: Not by itself. Ordinary dents, scrapes and faded paint are never defects, and corrosion only fails under this heading where a panel is damaged or corroded enough to be likely to cause injury when grazed, or is insecure. A panel likely to become detached is dangerous. A rotten but non-structural panel can therefore fail on its sharp edges alone.
What counts as a sharp edge at an MOT?: An edge or projection on a body panel, bumper, undertray, spoiler or mirror housing that could cut somebody who brushes against the car. Rust that has thinned metal until it leaves a hard, cut-like edge along an arch or a sill is the usual example. The test here is about injury and security rather than appearance.
Is a damaged or loose bumper an MOT failure?: It is if the bumper is insecure, or damaged so as to be likely to cause injury on contact, since both are major defects, and one likely to become detached is dangerous. Cosmetic cracks and scuffs are not defects, so a scraped but properly fixed bumper passes. Refitting one with the correct clips is £40 to £90.
Can I grind a sharp rusty edge off to pass the MOT?: Dressing the edge back with an angle grinder deals with the injury risk, so it can clear the failure. Be clear about what you have done, though: the rust is still spreading behind the paint, and filler over a rotten arch looks fine for a summer and comes back. Check for fuel lines, brake pipes and wiring behind the panel before you start.
How much does it cost to repair a rusty wheel arch?: Letting new metal into a rotten arch or sill is body-shop work at £200 to £500 per corner, mostly labour, and paint takes it to the top of the band once colour matching, blending and metallic finishes are involved. A secondhand panel from a breaker in the right colour is often the cheapest route on an older car. If the rot reaches a mounting point it becomes structural welding.

Cars this happens to most

Of every model with at least 2,000 tests in the DVSA data, these record body has a sharp edge likely to cause injury on the largest share of their MOTs. Across all of them the typical rate is 0.1% of tests.

Seat Exeo0.5%
20 times in 4,292 tests
Nissan E-NV2000.3%
21 times in 6,225 tests
MG GS0.3%
9 times in 2,849 tests
Nissan NV3000.3%
6 times in 2,311 tests
Smart (mcc) Forfour0.2%
46 times in 22,245 tests
Fiat Fullback0.2%
5 times in 2,788 tests
Mercedes-Benz Eqe0.2%
4 times in 2,343 tests
Kia Xceed 40.1%
3 times in 2,244 tests

A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.

Pass rates for every make and model

The warning light behind this

This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.

Door open warning lightWhat it means and whether you can keep driving

This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.

Has this been recorded on your car?

Check the full MOT history for any UK registration.