In the UK, an insurer writes off a car when it decides that repairing it isn't worth the money. In simple terms, that happens when the cost of repair, plus other costs, is close to or more than the car's pre-accident market value. It can also happen when a stolen car is never recovered, or when the damage makes a safe repair impractical.
There is no single legal percentage that triggers a write-off. Many people quote 50% to 60% of the car's value as a rule of thumb, but each insurer does its own sums, so treat that as a guide rather than a rule.
What insurers weigh up before writing off a car
When you make a claim, the insurer's engineer or assessor compares several figures:
- Repair estimate: parts, paint, labour and VAT where it applies.
- Pre-accident value: what a similar car would have sold for just before the incident.
- Salvage value: what the damaged car could be sold for at auction.
- Extra costs: recovery, storage and a courtesy or hire car while repairs are done.
- Safety: whether structural damage makes a safe repair impractical.
If repairing the car would cost more than paying out its value and selling the wreck, the insurer will usually declare a total loss. That's why older, lower-value cars are written off more easily. A £2,500 hatchback with £1,800 of damage may be uneconomic to fix, while a £40,000 car with the same repair bill would simply be repaired.
Situations that commonly lead to a write-off
- Collisions causing heavy bodywork or structural damage.
- Fire, which can affect wiring, interior and the body.
- Flooding, because water damage to electrics can be costly and unpredictable.
- Theft, where the car isn't recovered or is found badly damaged.
- Airbag, chassis or electrical damage that is expensive to put right.
UK write-off categories: A, B, S and N
Since October 2017, insurers record write-offs under four categories on the Motor Insurance Anti-Fraud and Theft Register (MIAFTR):
- Cat A: scrap only. Nothing should be reused and the car must not return to the road.
- Cat B: break only. The body shell must be crushed, though some parts can be sold.
- Cat S: structural damage to the frame or chassis. Repairable, but only with a proper structural repair.
- Cat N: non-structural damage, such as electrical or cosmetic problems. Repairable, but still a write-off on record.
Before 2017 the labels were Cat C and Cat D (alongside the older A and B), so an older car may still carry one of those. They are broadly the predecessors of today's S and N, but they are not identical, so don't assume they mean the same thing.
What happens after a car is written off
The insurer typically pays the car's pre-accident market value, minus your excess. You may be able to keep the car, known as retaining the salvage, in which case the payout is reduced by the salvage value. Insurers are expected to report write-offs so they can be recorded and the vehicle's DVLA record updated.
A Cat S or Cat N car can be repaired and driven again, but it is usually worth less than an equivalent car with no write-off history. Some insurers charge more to cover these cars, and some decline them.
Why this matters when you're buying a used car
A written-off car can be repaired to a good standard, but a seller may not mention its history, and a poor repair can hide problems. A write-off only appears on the record if an insurer handled the claim. If the owner paid for repairs privately, the damage may never be recorded. The MOT history shows test results, advisories and mileage, but it does not tell you whether a car was written off.
Before you pay a deposit, run the car's registration through a vehicle history check on motorpeek.com to look for write-off markers, a stolen marker, outstanding finance and mileage inconsistencies. No check can catch everything, so also do the basics:
- Ask to see the V5C and service history, and compare the details with the car itself.
- Look for uneven panel gaps, mismatched paint and fresh underseal.
- Ask for repair invoices if the seller admits to previous damage.
- Consider an independent inspection before you commit.
Frequently asked questions
What percentage of damage means a car is written off?
There is no fixed legal percentage in the UK. Insurers commonly write a car off when repair costs approach roughly 50% to 60% of its value, but this varies by insurer. They also factor in salvage value, VAT and extra costs such as recovery and hire cars.
Can a written-off car go back on the road?
It depends on the category. Cat A and Cat B cars must not be put back on the road. Cat S (structural) and Cat N (non-structural) cars can be repaired and driven again, though they usually sell for less and can be costlier to insure.
Does a write-off show on a car's MOT history?
No. MOT history lists test results, advisories, failures and recorded mileage, but not insurance write-off status. To check for a write-off marker you need a vehicle history check that draws on insurance data such as MIAFTR.