MOT & ROADWORTHINESS · LAST REVIEWED: JUNE 2026
TL;DR: A cat car check is about insurance write-off categories: A and B for the most severe damage, and S and N for repairable cars. The MOT history alone does not label a car as a write-off, but a gap or a salvage retest can be a clue worth following up on the official records.
A cat car check is the process of finding out whether a used car has been written off by an insurer and, if so, under which category. The categories run from A and B for the most severely damaged vehicles to S and N for cars that were repairable. Knowing the category matters when buying a used car.
The MOT history does not directly state that a car is a write-off, but it can offer clues, and it sits alongside the official write-off and vehicle records that do. This guide explains the categories and how the MOT history fits into checking a car's past.
KEY FACTS
- Insurance write-off categories are A, B, S and N; A and B vehicles should never return to the road, while S and N can be repaired and re-registered.
- Category A means the vehicle must be crushed; category B means the body shell must be destroyed though some parts may be reused.
- Category S covers structural damage and category N covers non-structural damage, both repairable in principle.
- The MOT history on gov.uk shows test results and mileage but does not itself record a write-off category.
- Driving without a valid MOT can bring a fine of up to £1,000 under the Road Traffic Act 1988.
What the write-off categories mean
When an insurer decides a damaged car is not economic or safe to repair, it records the vehicle as a write-off under one of four categories. Category A is the most severe and means the entire vehicle must be crushed, including all parts. Category B means the body shell must be destroyed, although some serviceable parts may be salvaged.
Category S and category N apply to cars that can be repaired. Category S indicates structural damage, meaning the chassis or a structural section was affected, while category N indicates non-structural damage. A category S or N car can legally return to the road once properly repaired and re-registered where required.
How the MOT history can help
The gov.uk MOT history service does not carry a write-off marker, but it can still support a check. A long gap in the testing history, a sudden change in recorded mileage, or a test at an unfamiliar location can prompt a closer look. None of these prove a write-off, but they are reasons to ask more questions.
Reviewing the advisories over time can also reveal repairs or recurring issues. Combined with the official vehicle records, the MOT history helps build a picture of how a car has been used and maintained, which is part of sensible due diligence before buying.
Checking the official records
The definitive record of whether a vehicle was written off sits with the insurance industry and the official vehicle records rather than the MOT. The gov.uk guidance on scrapped, lost and written off vehicles explains how categories are recorded and what happens to a vehicle in each case.
For a category S or N car returning to the road, the work should have been carried out properly and the vehicle presented for an MOT. A buyer can use the MOT history to confirm the car has since passed and to see what was noted, while treating the category itself as the key fact to establish.
Why it matters when buying
A previously written off car can be sound once repaired, but the history affects value and should be disclosed. Buying without knowing the category risks paying too much or taking on a car whose repairs cannot be verified. The category is therefore one of the first things to establish.
Pairing a write-off check with the MOT history gives a fuller view: the category explains the car's past, and the MOT record shows whether it has been roadworthy since. Using the official sources for both keeps the check reliable.
Practical steps for a buyer
Approaching a used car purchase methodically reduces the risk of an unwelcome surprise. The starting point is the registration number and the V5C registration certificate, which should match the car in front of the buyer. The V5C identifies the registered keeper and the vehicle details, and a mismatch is a reason to pause.
With the registration to hand, the MOT history can be reviewed for the pattern of passes, failures and advisories, and for mileage that climbs sensibly year on year. A mileage figure that jumps backwards or stalls for a long period is worth questioning, because it can point to a fault in the record or, in the worst case, tampering.
The write off position is the separate piece that the MOT cannot supply. Establishing whether a car has ever been recorded under category A, B, S or N is part of basic due diligence, alongside any outstanding finance and the provenance of the vehicle. A category on its own is not a reason to walk away, but an undisclosed one is.
Pulling it together, a buyer who checks the V5C, reads the MOT history, confirms the mileage trend and establishes the write off status has covered the main bases. Each check uses an official or industry source, and together they give a far clearer picture than the seller's description alone.
Insurers also treat recorded categories differently at renewal. A Cat S or Cat N marker can raise premiums or narrow the panel of insurers willing to quote, so factoring the category into the purchase price matters as much as the repair history itself.
RELATED GUIDES
DISCLAIMER: This guide is general information, not professional advice. MOT rules and fees are set by the DVSA and can change. Check gov.uk for current requirements before acting.
Frequently Asked Questions
What do the car write-off categories mean?
Category A means the car must be crushed entirely. Category B means the body shell must be destroyed though some parts may be reused. Category S covers repairable structural damage, and category N covers repairable non-structural damage.
Does the MOT history show if a car is a write-off?
No. The gov.uk MOT history shows test results, mileage and advisories, but it does not record a write-off category. The write-off status is held in the insurance and vehicle records, so a separate check is needed.
Can a Cat S or Cat N car pass an MOT?
Yes. A category S or N car can be repaired and, once roadworthy, can pass an MOT and return to the road. The MOT history will then show those later passes, but it will not by itself reveal the earlier write-off.
How can the MOT history hint at a write-off?
A long gap in testing, an unexpected mileage change, or a test at an unusual location can be worth following up. These are clues rather than proof, so they should be checked against the official write-off and vehicle records.
