A corrosion advisory means rust was seen but the structure is not significantly weakened. Corrosion that significantly reduces structural rigidity is a major defect, and corrosion likely to affect steering or braking is dangerous. Areas within 30cm of body mountings are assessed separately.
Checked 23 October 2026 against the DVSA MOT inspection manual
- Rigidity significantly reduced: Major defect
- Steering or braking affected: Dangerous defect
- Body mountings: Checked within 30cm
- DVSA manual: 6.1.1 and 6.2
What this advisory means
An advisory is recorded when an item is not deteriorated enough to justify a fail, so the presenter is informed of the defect. It does not cause a fail and is recorded in the MOT history. For corrosion, this means rust has been noted but has not reached the threshold for a major or dangerous defect at the time of the test.
Structural rust is judged against the DVSA manual. Structure corroded so that the rigidity of the assembly is significantly reduced is a major defect under 6.1.1 c i. Corrosion likely to affect steering or braking is dangerous under 6.1.1 c ii. Corrosion within 30cm of body or cab mountings is assessed under 6.2.2, where excessive corrosion is major.
Body panels corroded so they could injure someone are a major defect under 6.2.1 a i. An advisory therefore signals that corrosion is present, while the fail thresholds rest on structural rigidity, risk to steering or braking, proximity to mountings and the chance of injury.
When it becomes an MOT fail
An advisory becomes a major defect when structure is corroded so that the rigidity of the assembly is significantly reduced, as set out in DVSA manual 6.1.1 c i. The same manual classifies corrosion likely to affect steering or braking as a dangerous defect under 6.1.1 c ii. A dangerous result means the vehicle must not be driven until the fault is rectified.
Corrosion within 30cm of body or cab mountings is assessed under 6.2.2. Where that corrosion is excessive, the defect is recorded as major. The 30cm measurement is taken from the mounting point, and the assessment covers the strength of the surrounding structure rather than surface appearance alone.
Body panels are treated separately. Corrosion that leaves a panel in a condition where it could injure someone is a major defect under 6.2.1 a i.
| DVSA manual ref | Defect | Result |
|---|---|---|
| 6.1.1 (c)(i) | Structure corroded, rigidity significantly reduced | Major |
| 6.1.1 (c)(ii) | Corrosion likely to affect steering or braking | Dangerous |
| 6.2.2 (d)(i) | Excessive corrosion at body or cab mounting points | Major |
| 6.2.1 (a)(i) | Corroded panel likely to cause injury | Major |
Source: DVSA manual section 6: body and structure, checked 23 October 2026.
Frequently asked questions
What is an MOT corrosion advisory?
An advisory is used when an item is not deteriorated enough to justify a fail, to inform the presenter. Advisories do not cause a fail and are recorded in the MOT history.
When does corrosion become a major defect?
Structure corroded so that the rigidity of the assembly is significantly reduced is a major defect under DVSA manual 6.1.1 c i. Corrosion likely to affect steering or braking is dangerous under 6.1.1 c ii.
How is corrosion near body or cab mountings assessed?
Corrosion within 30cm of body or cab mountings is assessed under 6.2.2. Excessive corrosion there is a major defect, so it can lead to a fail rather than an advisory.
Can corroded body panels cause a fail?
Yes. Body panels corroded so they could injure someone are a major defect under 6.2.1 a i. This is separate from structural corrosion assessed under 6.1.1.
Do advisories affect the MOT result?
No. Advisories do not cause a fail and are recorded in the MOT history. They inform the presenter of an item that is not deteriorated enough to justify a fail.
Part of the MOT guide series
MOT check: the full guide › MOT advisories
‹ MOT Advisory: Play in the Steering Rack: What It MeansMOT Advisory: Exhaust: What the Note Means ›
