The short answer
Body damage stops being worth fixing when the repair cost approaches or exceeds the car's value — at which point an insurer declares it a write-off (total loss). In the UK, write-offs are graded: Category A and B are scrap (the car, or at least the body shell, must be destroyed), while Category S (structural damage) and Category N (non-structural) can legally be repaired and returned to the road if done properly and re-registered. Insurers usually write off when repairs cost roughly more than a high proportion of the car's value, because it is uneconomic to fix. Whether to repair a borderline car yourself depends on the damage type, the car's value, and the safety of any structural repair — economics and safety together decide it.
"Write-off" is an economic judgement with safety categories attached, not simply a measure of damage severity. The sections below explain the categories and where the line sits.
Quick reference
- Write-off triggerRepair cost near/over car's value
- Cat AScrap only — must be crushed
- Cat BBody shell destroyed; some parts reused
- Cat SStructural damage, repairable
- Cat NNon-structural, repairable
How a write-off is decided
A car is written off when an insurer judges it a total loss — meaning it is uneconomic, unsafe, or both, to repair. The core test is financial: if the cost to repair the damage approaches or exceeds the car's pre-accident market value, the insurer pays out the value rather than funding the repair. Because labour and parts add up quickly, even damage that looks moderate can exceed the value of an older or lower-priced car, which is why modest cars are written off more readily than expensive ones with the same dent.
The threshold is not a fixed legal percentage — insurers apply their own economic assessment — but the principle is consistent: once repairs cost more than a high proportion of the car's worth, repairing it makes no commercial sense. Salvage value (what the damaged car is worth for parts or scrap) also feeds into the sum. This is a judgement about money and safety, not a statement that the car is physically impossible to fix.
The UK write-off categories
UK insurers grade write-offs into four categories that tell you whether a car can return to the road. Category A is the most severe: scrap only, the entire car must be crushed and no parts may be salvaged. Category B means the body shell must be destroyed, though some serviceable parts can be removed and reused; the car itself can never go back on the road. These two are about safety, not just cost.
Category S (structural) means the car suffered damage to its structural frame or chassis but can be professionally repaired and returned to the road, subject to proper repair and re-registration. Category N (non-structural) covers damage that is not to the structural frame — often electrical, cosmetic or mechanical — and is also repairable and road-legal once fixed. A car in Cat S or N can be bought, repaired and driven, but the write-off is recorded against its history, which affects value and must be declared. The table summarises them.
| Category | Meaning | Back on the road? |
|---|---|---|
| A | Scrap — entire car crushed | No |
| B | Body shell destroyed, parts reused | No |
| S | Structural damage, repairable | Yes, if properly repaired |
| N | Non-structural, repairable | Yes, if properly repaired |
Indicative summary of UK salvage categories. A recorded write-off must be declared and affects value.
Repairing a borderline car yourself
If a car is a borderline write-off, you sometimes have the option to keep it and repair it yourself rather than accept a total-loss payout (the insurer deducts the salvage value). Whether that is wise depends on three things. First, the economics: can the damage be repaired for meaningfully less than the car's value, perhaps using good used panels? Second, the damage type: cosmetic and non-structural damage (Cat N territory) is far safer to take on than structural damage, which requires correct methods, jigs and re-testing to be safe. Third, the history impact: a recorded write-off lowers resale value and must be declared, so the car may be worth less afterwards even when well repaired.
The honest conclusion: body damage is not worth fixing once the proper repair cost outstrips the car's value, which is exactly when insurers write a car off. For Cat A and B, repair is not an option — the car is finished. For Cat S and N, repair is legal and sometimes sensible, but only when the sums work and, for structural damage, the repair is done to a safe standard. Where structural integrity is in doubt, do not cut corners; an unsafe structural repair is worse than no repair at all.
Frequently asked questions
What's the difference between Category S and Category N write-offs?
Category S means the car had structural damage to its frame or chassis but can be professionally repaired and returned to the road. Category N means the damage was non-structural — often cosmetic, electrical or mechanical — and is also repairable. Both can be driven once properly fixed, but Cat S involves structural repair and is the more serious of the two.
When does an insurer write a car off?
When the cost to repair the damage approaches or exceeds the car's market value, making repair uneconomic, or when the damage is too severe to repair safely. There is no fixed legal percentage — insurers apply their own assessment, factoring in repair cost, the car's value and its salvage value.
Can you drive a written-off car?
Only if it is Category S or N and has been properly repaired and re-registered as required. Category A and B write-offs can never return to the road — Cat A must be entirely scrapped and Cat B's body shell destroyed. Any write-off history must be declared when selling, as it affects the car's value.
Sources & further reading
- Which? — car insurance write-off categories explained
- gov.uk — vehicle salvage and write-off (insurance write-offs)
Figures on this page are typical UK ranges drawn from published sources and depend on your specific car and damage. They are guidance, not a quotation.