Used Car Buying Guide
What the categories actually mean — Cat S, Cat N, Cat A and Cat B — and what to do if you find one.
The letter appears almost as an afterthought. "Cat S — fully repaired." And most buyers either don't know what it means, or take the seller's word that it's fine.
Here's what it actually means.
In 2017, the insurance industry changed how it classifies damaged vehicles. The old Cat C and Cat D were replaced with Cat S and Cat N. A lot of listings still use the old terms. A lot of buyers are still confused by both.
If you see Cat C or Cat D on a listing, treat it as Cat S or Cat N respectively — and apply everything below.
The car must be destroyed entirely. It cannot return to the road. No parts, no repairs, no exceptions. If you see a Cat A car for sale, walk away and report it.
The body shell must be crushed, but salvageable parts can be removed first. Like Cat A, a Cat B car should never be on a road. If it is, something has gone seriously wrong.
The frame or chassis was damaged significantly enough that the insurer wrote the car off. It can be repaired and returned to the road. It must be declared on every future sale.
Bodywork, electrics, trim. The insurer wrote it off because the repair cost wasn't worth it to them — not because the frame was affected. Also must be declared on every future sale.
A properly repaired Cat S can be roadworthy. But the structural frame is what protects you in another accident. If the repair wasn't done correctly, crumple zones may not perform as designed. Alignment issues develop over time. Corrosion starts at repair points and stays invisible until it's serious.
An MOT won't catch any of this. MOTs check that a car is roadworthy on the day. They don't inspect the quality of structural repairs.
A Cat S or Cat N stays on the record of that vehicle permanently. Every future buyer will see it. Every insurer will price it differently. When you come to sell, you'll be competing against clean cars — and the history will cost you.
So the price you pay now should reflect that.
Ask what the clean market value is. Look it up. If the Cat S car is priced anywhere near that figure, walk away. The discount isn't a bonus. It's the only reason a Cat S car makes financial sense to buy.
No discount. No deal.
If you work in the trade, you might be perfectly happy with a Cat S. You understand what you're looking at. You know what a good structural repair looks like. You want that high-spec car at a knock-down price and you know how to protect yourself.
That's fine. This post isn't for you.
For everyone else — a first-time buyer, someone who needs a reliable car and can't afford to get it wrong — the advice is simpler.
Declared Cat S or N: Unless you genuinely know what you're doing and can get a truly independent structural inspection, walk away. There are plenty of clean cars. Find one of those instead.
Undeclared Cat S or N: This one isn't a car decision. It's a people decision. The seller already lied to you — before you met them, before you asked a single question. The car might be perfectly repaired. It doesn't matter. If the first thing they did was hide the history, what else aren't they telling you?
No damage history found. Clean record on this vehicle.
Cat N declared. Non-structural damage on record. Seller has declared it. Check the price reflects the history — and consider an independent inspection before committing.
Cat S not declared in listing. Structural damage found on this vehicle's record. It was not mentioned in the listing. We wouldn't be comfortable with our own people driving this one.
Run the free check before the viewing. If there's a Cat S or N on this car's record — declared or not — you'll know before you get in the car.