Where the categories come from
When an insurer decides a repair costs more than a car is worth, or the damage is severe enough that repair isn't sensible, they record it as a total loss and assign a damage category under the ABI's code of practice. The category is about what kind of damage the car had, not simply how expensive the repair was.
Cat S vs Cat N
- Cat S (structural): the damage affected the chassis or load-bearing parts. A Cat S car can be legally repaired and put back on the road, and plenty are repaired properly, but structural repairs are harder to verify from the outside, so quality depends entirely on who did the work.
- Cat N (non-structural): damage didn't touch the structure, such as damaged trim, electronics or bodywork that doesn't affect the frame. It's often less serious, but "non-structural" can still include a badly damaged interior or safety systems, so it's not automatically minor.
Checking the category before you buy
A car's write-off history is recorded against its registration, not something a seller can hide by not mentioning it. Before agreeing a price, run a dedicated check such as MOTCO's write-off check to confirm whether a category is recorded and which one it is.
For anything you're seriously considering, ask who carried out the structural repair and to what standard, and factor that into your offer.
Common questions
Does insurance cost more for a Cat N or Cat S car?
Often yes, and it can be harder to arrange with some insurers. It's worth getting an insurance quote before committing to buy a written-off car, not after.
Can a Cat S car be sold as a normal used car?
Yes, once legally repaired it can be sold and driven, but its write-off history stays on record permanently and usually reduces resale value regardless of repair quality.