A high percentage of used cars in the UK show signs of digital tampering to hide their true history or identity.
More than one in seven vehicles (16.25 percent) has potentially had its mileage wound back, or the VIN (Vehicle Identification Number) manipulated.
Both actions mean used car customers might unwittingly pay more for a vehicle than it is actually worth. They could also be unaware of serious mechanical defects.
Previous research has found the UK is the worst-affected country in Europe for odometer tampering, also known as clocking.
Hidden car history exposed
Automotive diagnostics platform Carly uncovered the new data on mileage tampering and VIN manipulation by analysing vehicle diagnostic data.
More than 2.5 million Carly diagnostic sessions were included, covering over 550,000 cars tested in the UK between January and September 2025.
The Carly platform connects directly to a vehicle’s internal systems via the OBD (on-board diagnostics) port. This allows mileage readings and VIN records across multiple components to be compared, helping to identify any inconsistencies.
Such issues would not typically be obvious through a basic visual inspection alone.
Helping used car buyers be informed
Carly’s research found that major cities and ports displayed higher levels of vehicle manipulation, due to a larger number of vehicle transactions. However, there was no great variance across the country.
It means used car customers in the north of Scotland are as likely to encounter a vehicle with a hidden history as those in the south of England.
Commenting on the findings, Dali Ati, head of internationalisation at Carly, said: “Mileage tampering can make a car appear newer and more valuable than it really is. But beneath the surface, it could be far more worn and that’s where unexpected problems begin.
“We want drivers to feel informed and in control before they spend their money. A quick Carly scan, using the Carly Used Car Check, can uncover these hidden issues in just minutes. And the best part? The scanner costs as little as £41, and these checks can save buyers thousands.”
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