Cat S vs Cat N Write-Offs Explained

What Cat S and Cat N write-offs mean, whether they're safe to buy, how they affect value, and how to check repairs went through official dealers.

FindServiceHistory · Vehicle History Experts

Published 2 July 2026

Written by FindServiceHistory

What Is a Written-Off Car?

A car is "written off" when an insurer decides it is uneconomical or unsafe to repair after damage — usually from a collision, flood or fire. That does not always mean the car is scrap. Many written-off cars are repaired and returned to the road perfectly legally, sold on at a lower price. The write-off is recorded against the vehicle permanently, and it is classified into a category that tells you how serious the original damage was.

Since October 2017 there have been four categories. The two you are most likely to encounter on a car that is back on sale are Cat S and Cat N.

The Four Write-Off Categories

Category A — scrap only. The whole vehicle must be crushed, including parts. It should never be back on the road.
Category B — the body shell must be crushed, but some parts can be salvaged. Also should never be back on the road as a whole car.
Category S (Structural) — structural damage that has been (or can be) repaired. Safe to return to the road once properly repaired and re-registered.
Category N (Non-structural) — damage that did not affect the structural frame. Can be cosmetic, electrical, or to bolt-on components. Also road-legal after repair.

Cat S vs Cat N: The Key Difference

The distinction is about where the damage was, not how expensive it was to fix.

Cat S means the structural, load-bearing parts of the car — the chassis, crumple zones, pillars or subframe — were damaged. These parts are designed to protect occupants in a crash, so the quality of the repair genuinely matters for safety. A well-repaired Cat S car can be sound; a badly repaired one can be dangerous.
Cat N means the structure was untouched. The damage might still have been significant — think airbags, electronics, lights, or panels — but nothing load-bearing. Cat N is generally considered the lower-risk of the two, though "non-structural" does not automatically mean minor.

Should You Buy a Cat S or Cat N Car?

There is nothing inherently wrong with buying a repaired write-off — the discount can be substantial and the car can be perfectly sound. But the risk sits entirely in the quality of the repair, so protect yourself:

Get an independent inspection from a qualified mechanic or a specialist who can assess repaired structural work.
Ask for photographs of the damage and receipts for the repair.
Factor in the resale hit — the marker follows the car, so you will take the same discount again when you sell.
Check whether repairs and ongoing servicing went through franchised dealers, which points to a more careful owner.

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How to Check a Car's Write-Off Status — and Its Repairs

The write-off category itself shows up on an HPI-style provenance check — see what is an HPI check for how those work. That is the check you run first to discover whether a car has a Cat S or Cat N marker at all.

What it will not tell you is whether the repairs and later servicing were done to a proper standard. That is where a service history check helps: it reveals whether the car's work went through franchised dealers, with dates, mileage and the jobs carried out — a genuine signal of how seriously it has been maintained since the accident. Enter the registration; it is £9.99 with no charge if no records are found, and full MOT history is included free.

For the complete pre-purchase picture, see our vehicle history guide.

Frequently Asked Questions

What is the difference between Cat S and Cat N?

Cat S (Structural) means the car suffered structural damage — to the chassis, crumple zones or other load-bearing parts — that has since been repaired. Cat N (Non-structural) means the damage did not affect the structure; it could be cosmetic, electrical, or to bolt-on panels. Both were declared insurance write-offs, but Cat S involved more serious underlying damage.

Is it safe to buy a Cat S or Cat N car?

It can be, if the repair was done properly and documented. Many Cat S and Cat N cars are repaired to a high standard and sold on legitimately at a discount. The risk is a poor or hidden repair, so you should insist on evidence of the work, ideally an independent inspection, and confirmation that any mechanical or dealer work is on record.

How much less is a Cat S or Cat N car worth?

As a rough guide, a Cat N car typically sells for around 15-25% less than an equivalent clean car, and a Cat S car around 20-40% less, depending on the model, the severity of the original damage and the quality of the repair. The write-off marker stays on the car's record permanently and will affect resale too.

Does a service history check show if a car was written off?

No — write-off categories appear on an HPI-style provenance check, not a service history check. What a service history check adds is different but valuable: it shows whether post-accident repairs and ongoing servicing went through franchised dealers, which is a useful signal of how seriously the car has been maintained since.

What happened to Cat C and Cat D?

Cat C and Cat D were the old categories, replaced in October 2017 by Cat S and Cat N. Older cars may still carry a Cat C or Cat D marker on their record. Broadly, Cat C maps to today's Cat S (more serious) and Cat D to Cat N (less serious), though the assessment criteria changed.