Introduction
A write-off is a car an insurer has declared beyond economical repair, usually once the cost of fixing it reaches somewhere between 50 and 70 percent of its market value. Every write-off gets sorted into one of four categories reflecting how severe the damage actually is, and understanding the difference matters enormously if you're buying used since two of the four categories describe cars that can legally return to the road.
For everything else worth checking before you buy, see our complete guide to buying a used car.
Summary:
- Cat A and Cat B cars must be scrapped. Neither can legally return to the road under any circumstances.
- Cat S and Cat N cars can be repaired and driven again, provided the work is done properly and documented.
- Cat S means structural damage. Cat N means everything else, cosmetic, electrical or mechanical damage that doesn't touch the car's frame.
- Cat C and Cat D no longer exist for new write-offs, replaced by Cat S and Cat N in October 2017, though older cars still carry their original label.
- A write-off history permanently reduces a car's value, even once properly repaired, and must be disclosed to any future buyer.
What Is a Cat A, B, S or N Insurance Write-Off?
An insurance write-off is a car that's sustained enough damage that repairing it doesn't make financial sense for the insurer, who pays out the car's value instead of fixing it. The exact threshold varies by insurer. Repair costs reaching roughly 50 to 70 percent of the car's market value typically trigger this decision though, once assessors factor in labour, parts and additional costs like recovery and storage.
Every write-off gets assigned one of four categories, set out by the Association of British Insurers' salvage code. The categories moved away from grading purely by repair cost in 2017, focusing instead on whether the damage is structural since that's what actually determines whether a car can safely return to the road. Read our full guide what happens if your car is written-off.
Write-Off Categories at a Glance
| Category | Structural Damage | Repairable | Can Return to Road |
|---|---|---|---|
| Cat A | Yes | No | No |
| Cat B | Yes | No | No |
| Cat S | Yes | Yes | Yes |
| Cat N | No | Yes | Yes |
What Is a Cat A Write-Off?
A Cat A write-off is destined for scrap only, with no exceptions. The entire vehicle gets crushed, and a Certificate of Destruction is issued once disposal is complete. Even components that still technically work, an intact engine or a working stereo, must be destroyed alongside everything else. Nothing from a Cat A car can legally reappear on the road or in another vehicle.
What Is a Cat B Write-Off?
A Cat B write-off has suffered severe damage too, though not quite as catastrophic as Cat A. The body shell must still be crushed and can never return to the road. Specific components though, an engine, gearbox or other mechanical parts, can be salvaged and reused in other vehicles. The insurer typically handles disposal directly once the claim settles, with no responsibility falling on the original owner.
What Is a Cat S Write-Off?
A Cat S write-off means the car has suffered genuine structural damage, affecting parts like the chassis, crumple zones, floor pan or the A and B pillars that form the car's safety cell, the key difference from Cat A and Cat B being that a Cat S car can be professionally repaired and legally driven again once the work is properly documented and the car passes the necessary safety checks.
The exact registration process afterward varies slightly depending on who you ask. Some guidance describes this as needing to be "re-registered" with the DVLA before returning to the road. Other sources note the car keeps its original registration number instead, with the write-off status simply recorded permanently against that number rather than requiring a fresh plate. Either way, the practical outcome is the same. A Cat S car's history stays visible forever, declared honestly to any future buyer.
What Is a Cat N Write-Off?
A Cat N write-off covers everything that isn't structural, cosmetic bodywork damage, electrical faults, interior damage or non-structural suspension components like control arms. The car's underlying frame remains untouched. Once repaired, a Cat N car needs to pass a standard MOT to return to the road, without the same additional structural inspection a Cat S car needs though.
What Were Cat C and Cat D? (And Why Did They Change?)
Before October 2017, write-offs used a different system. Cat C meant repair costs exceeded the car's value. Cat D meant the car was cheaper to repair than replace, though the insurer still judged it uneconomical once every cost was factored in. As cars became more complex and repair bills grew accordingly, this system increasingly wrote off cars for reasons that had nothing to do with genuine safety.
The switch to Cat S and Cat N shifted the focus from pure repair cost to whether the damage was structural, a more meaningful distinction for anyone considering buying one of these cars afterward. Any car categorised before October 2017 keeps its original Cat C or Cat D label permanently, which is why you'll still see these terms on older used car listings.
Real Examples of Damage in Each Category
Seeing what actually causes each category makes the definitions easier to picture. A Cat A car might have been fully burnt out in a fire or crushed in a serious head-on collision, damage severe enough that nothing about the vehicle is worth salvaging at all. A Cat B car often comes from a similarly serious accident, though with the engine, gearbox or other major components surviving intact enough to be reused elsewhere, even though the body itself is beyond saving.
Cat S typically results from a moderate to serious collision bending the chassis or crumpling the floor pan, a rollover accident damaging the roof structure, or flood damage compromising the vehicle's underlying frame. Cat N covers a much wider range of everyday scenarios, a stolen and recovered car with damaged locks and wiring, hail damage across every panel, a small kitchen fire limited to the interior, or even a car that suffered water damage to its electrics during flooding without the frame itself being affected.
What Happens to a Car Physically After It's Written Off?
Once your insurer settles the claim, ownership of the car typically passes to them, and what happens next depends entirely on the category assigned. Cat A and Cat B vehicles go to an authorised treatment facility, a licensed site equipped to crush the vehicle and, for Cat A specifically, destroy any remaining parts too, with a Certificate of Destruction issued once the process is complete.
Cat S and Cat N cars usually enter the salvage market instead, sold at dedicated salvage auctions to professional repairers, parts traders or sometimes the original owner buying the car back directly. A specialist repairer buying a Cat S car at auction will typically assess the full extent of the damage, source the necessary parts and carry out the structural repair before the car can legally return to the road, a process that can take considerably longer than a routine repair given the additional documentation and safety checks involved.
Can You Legally Drive, Insure and Finance Each Category?
Cat A and Cat B
Never, under any circumstances. Both categories are permanently barred from the road. Neither can be legally insured, financed or driven again in any form.
Cat S and Cat N
Yes, once properly repaired and, for Cat S specifically, confirmed roadworthy through the appropriate checks. Insurance remains available for both, though premiums typically run higher than for an equivalent car without a write-off history, and some insurers decline to cover either category entirely. Always confirm cover is genuinely available before committing to buy.
For the full detail on how premiums are calculated more broadly, see our guide on getting cheap car insurance.
How Does a Write-Off Affect Resale Value?
Permanently and considerably. Even a Cat S or Cat N car repaired to an excellent standard will sell for less than an equivalent car without that history since the write-off marker stays recorded against the vehicle forever and must be disclosed to any future buyer, exactly why these cars cost less to buy in the first place. Worth factoring the same reduced value in whenever you eventually come to sell.
Does a Write-Off Category Affect MOT or Car Tax?
Not directly, though the underlying damage often does. A repaired Cat S or Cat N car still needs to pass a standard MOT to stay legally on the road, exactly the same requirement as any other car, covered in full in our guide on how the MOT test works. The write-off category itself doesn't add any extra MOT requirement beyond this, though a poorly repaired car is naturally more likely to fail on the specific items the damage originally affected.
Car tax works independently of write-off history too, calculated the same way for a repaired write-off as for any other car of the same age and specification, detailed fully in our guide on car tax explained. Neither system asks about write-off history directly, though a genuine history check will always reveal it regardless.
How Can You Check If a Car Has Been Written Off?
Every UK write-off gets recorded on the Motor Insurance Anti-Fraud and Theft Register, the database insurers use to log total loss vehicles, and this is exactly what a vehicle history check searches to confirm a car's write-off status.
For the full process of running this check alongside everything else worth verifying before buying, see our guide on how to check a used car's history.
Should You Buy a Cat S or Cat N Car?
The Case For
A genuinely lower purchase price is the main draw, often significantly below an equivalent car without a write-off history. If the repair work has been done properly by a competent professional, there's no inherent reason a Cat S or Cat N car can't provide years of reliable use afterward.
The Case Against
Resale value takes a permanent hit regardless of repair quality, and insurance typically costs more, sometimes considerably so for Cat S specifically. Verifying repair quality is harder than checking a car with no such history since you're relying on someone else's work rather than a documented, unbroken history.
Questions to Ask Before Buying One
Ask for full documentation of the original damage and the repair carried out, ideally including photos. Request confirmation of who performed the repair and whether it's been independently inspected since. Confirm you can actually get insurance for the specific car before committing since cover isn't guaranteed.
Buying through a reputable dealer rather than a private sale generally offers stronger consumer protection if something turns out to be wrong, alongside the wider set of questions worth asking any seller, covered in full in our guide on questions to ask when buying a used car.
What If You're Not Happy With a Cat S or Cat N Repair?
Raise it with the insurer or repairer directly and as soon as possible, regardless of how minor the concern seems. An independent inspection, available through organisations like the AA or RAC, gives you a documented report to support your case, and it's worth explaining exactly what work was carried out so the inspector knows what to check specifically.
If the issues aren't resolved after raising them, you may be entitled to escalate the complaint further or seek a financial settlement, with the Financial Ombudsman Service available as a last resort if a direct resolution can't be reached.
Common Myths About Write-Off Categories
"Cat S always means a dangerous car." Not once properly repaired and documented. The category describes the type of damage that occurred, not the current condition of a specific car after professional repair.
"Any write-off is a bad buy." Not necessarily. Cat A and Cat B genuinely can't return to the road. A well repaired Cat S or Cat N car can be a sound purchase at a genuinely reduced price though, provided you've done the proper checks first.
"Cat N only ever means cosmetic damage." Not quite. Cat N covers a wider range than cosmetic issues alone, including electrical faults and non-structural mechanical damage like suspension components, none of which affects the car's structural frame but can still be a meaningful repair.
Frequently Asked Questions
Is it illegal to drive a Cat A or Cat B car? Yes, both categories are permanently barred from the road under any circumstances, regardless of any repair work carried out.
Where do Cat S and Cat N cars actually get sold? Mostly through dedicated salvage auctions, where professional repairers and parts traders buy damaged vehicles before repairing and reselling them, rather than through typical used car listings alone.
Does a write-off category ever get removed from a car's history? No, once recorded it stays permanently against that specific vehicle regardless of how many times it's bought, sold or repaired afterward.
Do Cat S and Cat N cars need a new registration number? No. Both keep their original registration, with the write-off status recorded permanently against that number rather than requiring a fresh plate.
Can I get GAP insurance to cover a write-off shortfall? Yes, if you already hold GAP insurance, it can cover the difference between your insurer's payout and any outstanding finance still owed on the car.
Are Cat S cars more expensive to insure than Cat N? Generally yes since Cat S reflects more severe, structural damage, which insurers typically view as a higher risk than the non-structural damage covered under Cat N.
Can I dispute my insurer's write-off decision? Yes, though you'll need solid evidence, such as independent repair quotes and proof of the car's genuine market value, to support a successful challenge.
Conclusion
The category attached to a written-off car tells you far more than the label itself suggests. Cat A and Cat B mean the car is gone for good, no exceptions, no buy-backs, no reappearing on the road under any circumstances. Cat S and Cat N describe a genuinely different situation entirely, cars that can be properly repaired and driven again, often at a real saving over an equivalent car without that history. The right approach isn't avoiding write-offs altogether.
A well repaired Cat S or Cat N car can be a sound purchase. Going in with your eyes open is what genuinely matters. Get the history check, ask for the repair evidence, confirm insurance is available, and treat the reduced price as fair compensation for a car that will always be worth somewhat less when you come to sell it.
At Car Planet, every vehicle undergoes a comprehensive history check before being listed, including checks against insurance write-off databases. You know exactly what you're buying, write-off history included.
