A car described as written off has not necessarily been destroyed. The decision is an economic one, and understanding how it is reached explains why lightly damaged cars are sometimes declared total losses.
What the calculation compares
An insurer compares the estimated cost of repair against the vehicle's market value immediately before the incident.
Market value means what the car would have sold for in its actual condition and mileage, not what a replacement would cost new.
Because older cars have low market values, a moderate repair bill can exceed that value even when the damage looks minor.
Why salvage value shifts the threshold
A damaged car retains worth as parts or as a repairable vehicle, and an insurer recovers some of its outlay by selling the salvage.
That recovery means the write-off point sits below the vehicle's full value rather than at it, often well below.
An insurer settling at market value and then selling the wreck can be better off than paying for a repair costing somewhat less, which is why the threshold is a proportion rather than a straight comparison.
What drives repair estimates upward
Modern bodies use bonded and high-strength materials that frequently cannot be straightened and must be replaced as complete sections.
Sensors, cameras and radar units mounted in bumpers, mirrors and windscreens add cost, and many require calibration after replacement.
Labour to remove and refit interior trim, and to access structure behind it, often exceeds the price of the visible damaged panel.
How categories differ
Write-offs are classified by how badly the structure is affected, and the categories separate vehicles that may return to the road from those that may not.
The most severe classifications require the vehicle to be dismantled or destroyed, because structural damage cannot be reliably repaired to a safe standard.
Lesser classifications allow repair and reregistration, and the classification is recorded permanently against the vehicle's identity.
What it means for the owner
A settlement is based on the insurer's assessment of market value, and an owner who believes that assessment is low can present evidence of comparable vehicles for sale.
Retaining the salvage is sometimes possible, in which case the salvage value is deducted from the payment and the car remains with the owner.
A recorded write-off follows the vehicle thereafter and reduces its value permanently, which is why the record matters to any subsequent buyer as much as the repair quality does.