Car terms. Explained.

A defect the MOT tester noted that is not bad enough to fail, but may need work soon. The same advisory year after year is worth asking the seller about.

The most serious write-off categories. A Cat A car must be crushed whole. A Cat B car can be stripped for parts, but its body must be crushed. Neither can legally return to the road.

Written off with non-structural damage, such as panels, lights or trim. It can be repaired and driven again, and is usually worth less than the same car with no record.

Written off with structural damage, such as a bent chassis or crumple zone. It can return to the road once properly repaired, and the insurer will usually ask how.

Winding back the odometer so a car looks less used. A reading lower than an earlier MOT is the usual sign.

Grams of carbon dioxide per kilometre. For cars first registered between March 2001 and March 2017 it sets the yearly road tax band. For newer cars it only sets the first year's rate.

The Driver and Vehicle Licensing Agency. It keeps the record of every UK vehicle: its keeper, tax, SORN status and basic details.

The Driver and Vehicle Standards Agency. It runs the MOT scheme and holds the result of every test, with mileage and advisories.

The exhaust standard a vehicle was built to, from Euro 1 to Euro 6. It decides whether a car meets ULEZ and other clean air zones.

The date the vehicle was first registered in the UK. For an import this can be years after it was built.

A car brought into the UK privately, not through the maker's UK dealers. Parts, servicing and insurance can cost more.

On HP or PCP the finance company owns the car until the last payment. Selling it before then without settling can leave the buyer in a dispute with the lender.

The person registered with the DVLA as responsible for the car. The keeper is not always the legal owner.

A recorded mileage lower than an earlier reading. It can be a typing error at a test centre, or a sign of clocking.

The yearly roadworthiness and emissions test for most vehicles once they are three years old.

Money still owed on a finance agreement secured on the car. It is a common hidden problem on a used car, and a history check looks for it.

A private number moved on or off a car. The car's history follows its VIN, so a new plate does not wipe the record.

Issued when the DVLA cannot confirm a vehicle's age or identity, often after a rebuild from parts or a kit car.

A manufacturer's safety fix for a known fault. The repair is free at a franchised dealer, whoever owns the car.

Vehicle Excise Duty, paid to the DVLA to use a vehicle on public roads. It does not transfer when a car is sold.

A vehicle sold through a salvage auction, usually after an insurance claim. Auction photos can show the damage before repair.

Statutory Off Road Notification. The keeper has told the DVLA the vehicle is off the road, so it cannot be driven or parked on a public road.

A police record that the vehicle has been reported stolen. A stolen car can be taken back, even from a buyer who paid in good faith.

The category a vehicle was approved under, such as M1 for cars and N1 for vans.

London's Ultra Low Emission Zone. Petrol cars usually need Euro 4 and diesels Euro 6 to drive in without a daily charge.

The vehicle registration certificate. It names the registered keeper, and its VIN must match the one on the car.

The 17-character vehicle identification number on the chassis and windscreen. It identifies the car even when the plate changes.

How the DVLA describes a vehicle's axles. Most cars are 2 axle rigid body.

A vehicle an insurer decided was not worth repairing after an accident, theft or flood. Its category says whether it can return to the road.