Cat S, Cat N, Cat C and Cat D: What Insurance Write-Off Categories Really Mean

You’ve found a car you really like. The photos look tidy, the mileage is sensible, and then you spot it in the small print: Cat N. Or maybe you’re the one selling, and a buyer has just asked a question you can’t answer. Either way, those few letters matter more than almost anything else in the advert — and the good news is they’re not automatically a reason to run.

What “written off” actually means

An insurer writes a car off when the cost of repairing it outweighs what the car is worth. That’s a financial decision, not a physical one. A twelve-year-old hatchback with a dented boot, a cracked bumper and a smashed rear light can be declared a total loss simply because the bodyshop quote comes to more than 60-70% of the car’s value.

Plenty of write-offs are, in reality, lightly damaged cars that an insurer couldn’t justify fixing. Plenty of others are genuinely bent. The category is your only clue as to which one you’re looking at — so it pays to know what each letter actually means.

The categories, in plain English

Since October 2017 the industry has used four letters: A, B, S and N. Anything written off before then was graded C or D, and those markers are permanent, so you’ll still see them on older adverts. Here’s the whole set.

Cat A — crush it, no exceptions

Structural damage plus fire or flood damage, or something similarly severe. A Cat A car must be crushed and no parts may be sold from it. It should never, ever reappear on the road. If you see one advertised, walk away and report it.

Cat B — body destroyed, parts sold

The bodyshell itself has to be destroyed, but salvageable parts can be sold on — wheels, engine, interior trim. A Cat B car cannot legally go back on the road. Be wary of anyone offering you one “cheap to fix”, because putting it back on the road isn’t allowed.

Cat S — structural (the old Cat C)

“S” stands for structural. The damage has reached the car’s framework — a crumpled chassis leg, a distorted floorpan, a bent sill. A Cat S car can legally be repaired and returned to the road, but it needs proper structural work by someone who knows what they’re doing, followed by an MOT. The marker stays with the car forever, even if you change the number plate.

Cat N — non-structural (the old Cat D)

“N” means non-structural. The damage didn’t touch the frame — a bumper, headlight, wing, door skin, tailgate or boot floor edge. These are usually the mildest write-offs and the easiest to repair properly. Like Cat S, a Cat N car goes back on the road with a permanent marker against it and needs to be road legal and MOT’d.

Cat C and Cat D — the old labels

Cat C was roughly today’s Cat S (structural) and Cat D roughly today’s Cat N (non-structural). Cars written off before October 2017 keep their original marker. They’re older now, so they sit firmly in bargain territory — but the same rules and risks apply.

What the category does to the price

Broadly speaking:

• Cat N cars sell for around 20-25% less than an equivalent clean example.
• Cat S cars sell for around 30-40% less.

Put numbers on it. A clean 2016 Ford Focus worth £8,000 might appear as a Cat N at £6,000-£6,400, or a Cat S at £4,800-£5,600. That’s thousands off for damage that may have been nothing more than a bumper and a headlight.

But the discount cuts both ways. When you sell, you’ll take a similar hit, and the pool of interested buyers is smaller. Buy a Cat S at 30% off and you’ll sell it at roughly 30% off too.

Why insurers and lenders care

You must declare a write-off marker when you buy insurance. Some insurers simply won’t quote for a Cat S. Others will cover it, but may only pay a reduced sum if the car is written off again. Hiding it can void your policy entirely — which is a very expensive way to save a few pounds a month.

Finance is the bigger obstacle. Most mainstream lenders won’t fund a Cat S or Cat N car on HP or PCP, so if you need a monthly payment deal, this probably isn’t the route for you.

How to check a car’s write-off history

Do these before you part with any money:

• Paid history check — HPI, Experian, RAC or AA, roughly £10-£25 for a single check. This is the one that flags the write-off marker, outstanding finance, stolen status and plate changes. Do it yourself rather than trusting the seller’s printout.
• Free DVLA MOT history at gov.uk — shows failures, advisories and any suspicious mileage gaps.
• The V5C logbook — check the keeper history matches the seller’s story. Note that the V5C does not show write-off status, so it proves nothing on its own.
• Ask for the repair invoice, bodyshop name and photos of the damage taken before the repair. A genuine seller will have them; a vague seller usually won’t.
• Get an independent inspection — AA or RAC inspections run around £150-£300 and can include a geometry check, which is exactly what a repaired Cat S needs.

Warning signs at the viewing

• Uneven panel gaps, or a bonnet or boot that doesn’t sit flush
• Overspray on rubbers, badges, arch liners or window trim
• Fresh welding along the inner wings, sills or floor
• Two slightly different paint shades in daylight
• Airbag warning light on, or a steering wheel that doesn’t match the interior’s wear
• Uneven tyre wear, or the car pulling to one side
• Cracks or odd sealant around the windscreen pillars
• A price more than 45% below book — usually too good even for a Cat S

Pre-purchase checklist for a Cat S or Cat N car

• Run the paid history check yourself
• See the repair invoice and pre-repair photographs
• Know the name of the bodyshop that did the work — and ideally ring them
• Book an independent inspection, including alignment figures
• Confirm your insurer will cover it and ask how they’d settle a future claim
• Get an insurance quote before you commit, not after
• Check airbags, seatbelt pretensioners and sensors all work
• Drive it at 60-70mph and brake hard in a straight line
• Keep copies of the advert, the history check and the paperwork

So — bargain or risk?

A Cat S or Cat N car is a bargain when you’re planning to keep it four or five years, the structural repair was done by a reputable bodyshop with alignment readings to prove it, you’ve had it independently inspected, you’ve got an insurance quote you can live with, and you’re paying 25-40% under clean book value.

It’s a risk when you need finance, when you’ll be selling in a year or two, when the paperwork is thin, when the seller is vague about the damage, when the saving is only 10-15%, or when it’s a Cat S with no photos and no bodyshop name. A Cat S on an expensive or high-performance car is a particular gamble, because structural repairs are far harder to get right and far more costly to put wrong.

A simple rule of thumb: a Cat N with photographs and receipts is often a genuinely sensible buy. A Cat S is a project unless the documentation is exceptional. And anything without paperwork at all — walk away, however tempting the price.

When you’re ready to make that change and want to sidestep the guesswork altogether, UpCars.uk is a good place to look, because every car there is checked over properly before it’s listed.