Updated May 2026 · By Bertram Sargla, founder of MOT Checkup

Cat S vs Cat N check: UK write-off guide 2026

Cat S = structural damage repaired. Cat N = non-structural damage repaired. Both are insurance write-offs under the 2017 ABI Code of Practice, both can legally return to UK roads after repair, and both will carry a permanent marker on every future history check. This page explains the four-category system (A / B / S / N), the insurance and resale impact, the limits of any "free Cat S check", and a buyer's decision rubric for whether to walk away or negotiate.

The four ABI categories at a glance

Where the categories come from

The current Cat A / B / S / N system was introduced in October 2017 by the Association of British Insurers, replacing the older Cat A / B / C / D categories. The change was driven by a long industry concern that the old "uneconomical-to-repair" labels (Cat C and D) confused buyers because they bundled together mechanically very different damage outcomes. The new categories split repairable write-offs cleanly along the structural vs non-structural line, which is the line that actually matters for future safety and resale.

The category is decided by the insurer's engineer at the point of total-loss assessment. It is recorded on the Motor Insurance Anti-Fraud and Theft Register (MIAFTR) and flows from there to the licensed retail data providers (HPI, RAC, AA, Total Car Check). A vehicle written off before October 2017 will appear with the legacy Cat C or Cat D marker indefinitely; the ABI did not retroactively re-label older records.

Insurance impact — what to expect on cover

Most mainstream comprehensive insurers will quote on a repaired Cat S or Cat N vehicle, but premiums are typically 10–25% higher than an equivalent clean-history car of the same age and value. A minority of insurers (especially for younger drivers, larger engines or higher market values) will decline outright. The declared category sits on the policy as a material fact — omitting it is grounds for the insurer to void cover and refuse a claim, even years later.

Specialist brokers like Adrian Flux, A-Plan and Brightside actively quote on Cat S and Cat N stock and tend to come in cheaper than a mainstream price-comparison quote for the same vehicle. If you're shopping a Cat S or Cat N as a deliberate value play, a 10-minute call to a specialist broker before you commit to the purchase is the right move — it confirms the car is insurable for you specifically at a premium you can live with.

Resale impact — the long-tail discount

The Cat S or Cat N marker is permanent. It does not "expire" or drop off the record after a number of years; every future buyer who runs a paid history check will see it. The market prices that permanence in: a Cat S vehicle typically transacts 20–40% below the clean-history book value for the same model and year. Cat N typically discounts 15–30%. The discount is widest on newer / higher-value cars (where the next buyer is most likely to be running a paid check) and narrowest on bangers under £2,000 (where the discount narrows because the absolute price floor is set by scrap value).

That permanence cuts both ways. As a buyer, you are buying the discount today and inheriting it on resale. The exit value is predictable: you do not "lose" the write-off discount when you sell, because the same marker will discount the next buyer's price by the same proportion. Cat S/N ownership is a value play with stable economics — not a depreciation trap, provided the purchase price already reflects the discount.

Should I buy a Cat S or Cat N car? — decision rubric

1. Confirm the category by paid check. Run a licensed history check (Total Car Check £7.95 minimum) to confirm Cat S vs Cat N — the seller's word is not the source of truth, and a small number of sellers misrepresent S as N because the discount is smaller.
2. Get the repair documentation. Ask the seller for the post-repair MOT certificate, any garage invoices, and (for Cat S) the DVLA re-registration confirmation. A vendor who cannot produce these on a £5k+ car is a vendor to walk away from.
3. Book an independent inspection. AA (£189–£249) and RAC (£199–£275) both inspect post-write-off vehicles specifically. For Cat S in particular, the inspection should include a chassis-alignment check and a panel-thickness gauge sweep.
4. Confirm insurability before committing. Get a specific quote on the specific VIN from at least one specialist broker. If the premium is workable, proceed; if every quote comes back as decline, the resale market will be equally thin and the discount you negotiated may not be deep enough.
5. Negotiate against the marker, not the book. Clean-history book value × (1 − category discount) is your ceiling, not your starting point. A repaired Cat S at 35% under book is a fair price; a Cat S at 10% under book is the seller hoping you don't run a history check.

How MOT Checkup handles write-off data

MOT Checkup's free tier covers the DVSA MOT history layer and DVLA Vehicle Enquiry data — useful for spotting MOT gaps that often coincide with a repair period after a Cat S claim, but not a substitute for the actual MIAFTR category. We do not currently license MIAFTR directly; for the confirmed ABI category we point users to a paid HPI-style check. See the /write-off-check guide for the paid-provider comparison and /methodology for the full exclusion list.

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