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The 10 cars that are most at risk of being fined for undeclared modifications have been revealed.
Research from car marketplace Cazoo and car insurance broker Tempcover found the models most frequently identified with modifications.
A survey of 2,000 UK drivers found that one in eight (13%) motorists report discovering undeclared modifications only after completing a used car purchase.
Among respondents who had not previously informed their insurer about modifications, 17% believed changes made by a previous owner did not need to be declared, highlighting a further knowledge gap among both buyers and sellers.
Undeclared modifications could see drivers face cancelled cover in the event of a collision.
Additionally, Claire Wills-McKissick, temporary car insurance expert at Tempcover, said that omitting material vehicle changes – even accidentally – can be treated as careless misrepresentation, or more seriously, insurance fraud if the concealment is deliberate.
Insurance fraud can see your insurance cancelled, as well as potential fines and penalty points depending on the severity of the case.
Wills-McKissick recommends that motorists check their vehicle handbooks, review policy terms, and speak directly with their insurer if uncertain.
Top 10 cars most at risk of having undeclared modifications
According to research from Cazoo, the top 10 cars most likely to have undeclared modifications are:
- Volkswagen Golf GTI/R
- BMW 3 Series
- BMW 1 Series
- Audi A3/S3
- Audi A4
- Seat Leon FR/Cupra
- Skoda Octavia vRS
- Ford Fiesta ST
- Ford Focus ST
- Range Rover/Range Rover Sport
Michael Golson, motoring expert at Cazoo, said: "The biggest issue with many modifications is that a used car can look completely standard while hiding changes that affect its performance, reliability or insurance.
"Buyers shouldn’t be afraid to ask direct questions about remapping, gearbox software and whether the car has ever been modified and then returned to standard.
"A little extra scrutiny before buying could save you from an expensive surprise further down the road.
"The big risk is the cost of reversing it, as replacing tampered emissions equipment can easily run into four figures – with a replacement DPF costing around £1,000 to £3,500."
What car modifications are illegal in the UK?
According to Halfords, several vehicle modifications can fall foul of the law in the UK, including excessively tinted windows, neon lighting and overly loud exhaust systems.
Number plates are another common issue.
The retailer said drivers could face fines for using custom plates that do not meet DVLA rules on size, spacing and reflectivity.
Drivers can also get into trouble if accessories such as spoilers are not securely fitted, as modifications that pose a safety risk may attract police attention.
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Top 10 car modifications motorists don't know they are required to declare
Tempcover's research found the top 10 undeclared car modifications are:
- Unofficial Apple CarPlay, Android Auto, or touchscreen retrofits – 91%
- Non-factory parking sensors – 88%
- Upgraded sound system or speaker installations – 88%
- Retrofitted parking sensors – 87%
- Paint protection film (PPF), vinyl wraps, or body stickers/decals – 86%
- Installed towbars or roof racks – 86%
- Bulb replacement with brighter aftermarket lights – 82%
- Aftermarket alarms, immobilisers, or GPS trackers – 78%
- Non-factory alloy wheels, custom paint, or tinted windows – 77%
- Engine ECU remapping, chip tuning, or pedal boxes – 72%
Have you made any modifications to your car? Let us know in the comments.