Drivers across the UK are being advised to look out for a crucial warning sign when purchasing a used car, as experts caution that overlooking it could expose buyers to fraud, financial loss, or serious safety issues.
Motoring specialists are urging prospective buyers to carefully check a vehicle’s identification number (VIN) before finalising any purchase. The warning follows new research revealing hundreds of irregularities linked to VINs discovered during inspections last year.
Breakdown rescue provider Green Flag, which carried out the study, said problems with a vehicle’s VIN can often signal far more serious concerns. These issues may indicate that a car has been stolen, cloned, or improperly repaired following a major accident.
A VIN, or Vehicle Identification Number, is a unique 17-digit code stamped into a car’s chassis. According to the RAC, the number functions as the vehicle’s permanent identity, much like a fingerprint. Unlike registration plates or other identifiers, the VIN cannot be legally changed once the vehicle leaves the production line.
The structure of the number provides key information about the car. The first section identifies the country of origin and manufacturer—for example, the code “WAU” indicates a German-made Audi. The second portion describes the vehicle’s specifications, while the final section uniquely identifies that specific car.
VIN numbers play a crucial role in tracking recalls, verifying registration and insurance records, and reviewing vehicle history reports. They are typically located in several places on the car, including the dashboard near the windscreen, the driver’s side door frame, within the engine bay on the chassis, and on the vehicle’s official registration documents.
Green Flag uncovered the scale of potential issues through a Freedom of Information request to the Driver and Vehicle Standards Agency (DVSA). The request revealed that 449 VIN irregularities were identified during MOT tests in 2025.
Among the cases recorded were 138 instances where the VIN was illegible, 137 cases where different VINs appeared on the same vehicle, and 104 cases where the VIN was missing or could not be located. Inspectors also found 57 incomplete VINs and 13 cases where the number had been falsified.
Such irregularities can sometimes be linked to criminal activity. In some cases, stolen vehicles are given cloned VINs copied from legitimate cars to conceal their true identity. In other situations, vehicles that have suffered severe damage may be reconstructed using parts from multiple cars—a dangerous practice known as a “cut and shut”—with altered VINs used to disguise the repair.
Katie Lomas, managing director at Green Flag, said the VIN is central to confirming a vehicle’s legal identity and that any irregularities should raise immediate concern.
“A vehicle’s VIN is its legal identity, and when it is missing, illegible or appears to have been tampered with, it is often a warning sign of something far more serious,” she said. “That is why vehicles with VIN issues during an MOT test will fail and trigger further checks.”
Lomas added that such problems may indicate stolen vehicles, unsafe accident repairs, or even organised criminal activity.
She urged buyers—particularly those purchasing cars from private sellers—to carefully verify that the VIN on the vehicle matches the number recorded on its paperwork.
“Paying a small fee for a professional vehicle history check can help protect buyers from fraud, financial loss and safety risks,” she said.
