VIN (Vehicle Identification Number)

A Vehicle Identification Number, universally shortened to VIN, is the 17-character code that identifies one individual vehicle and no other. It is not a model code or a batch number: two cars built on the same day, in the same colour, to the same specification still carry different VINs. Standardised worldwide by ISO 3779 and mandatory on cars built since 1981 in most markets, it is the reference every other record hangs from — registration, insurance, recalls, service entries, customs paperwork and mileage readings are all filed against it.

The 17 characters divide into three blocks. The first three are the World Manufacturer Identifier, which names the maker and the country of assembly; a VIN starting WVW belongs to Volkswagen in Germany, WBA to BMW, VF1 to Renault in France. Characters four to eight are the Vehicle Descriptor Section, which encodes attributes such as body style, engine family, restraint system and series, according to a scheme each manufacturer defines for itself. Character nine is a check digit, calculated from all the others, so a VIN that has been altered by a single character will usually fail the arithmetic. Characters ten to seventeen form the Vehicle Identifier Section: position ten is the model year, position eleven the assembly plant, and the last six are the sequential serial number of that car coming down the line.

One detail catches people out. The letters I, O and Q never appear anywhere in a VIN, precisely because they are too easily mistaken for the digits 1 and 0. If you are reading a code off a dusty plate and think you see an O, it is a zero. On the car itself the VIN is stamped or riveted in several places at once: a plate visible through the base of the windscreen on the driver side, a sticker in the door jamb, and stamped directly into the bodyshell, often under the bonnet or beneath the trim next to a seat. It is repeated in the registration document and increasingly in the vehicle electronics.

That repetition is deliberate, and it is what makes the VIN useful when buying used. Because the number is the join key for every database that has ever touched the car, a single 17-character string is enough to pull together mileage readings taken at inspections and services, recorded damage, outstanding finance, theft records and import history from different countries. It is also why the number is worth checking physically rather than trusting the advert: a VIN that does not match between the windscreen plate, the door jamb and the paperwork, or one whose stamping looks re-cut, points at a car whose identity has been altered. What a VIN cannot do is tell you the condition of the car in front of you — it identifies the vehicle, and the history has to be looked up against it.