What is Cat N?

Cat N stands for Category N (Non-structural). It's used when a car has been written off, usually because repair costs outweighed its value, for damage that doesn't affect the structural safety of the car - for example cosmetic bodywork, electrical faults, or damage to non-structural parts.

What it means for a buyer: a Cat N car has been through an insurance write-off, but without the structural questions that come with a Cat S car. It's still worth taking seriously though - it's worth understanding the reason for the write-off, and like any write-off history, it's very likely to reduce the car's value compared to an equivalent car with no write-off history.

Source: gov.uk: insurance write-offs