How To Know If Your Car Mods Are Legal



Modifying your car can be an excellent way to boost power, improve performance and make your ride unique. From coilovers to turbos, there is a seemingly endless list of tweaks and changes you can make to improve your driving experience. That said, depending on your country’s road laws, not every modification is legal. Before you invest time and money into significant changes to your ride, it is crucial that you abide by the legal guidelines and declare all modifications to your insurance provider. Read on to find out more. 

What Classes As A Modification?

Any permanent or semi-permanent change made to a vehicle classes as a modification. For example:

  • Suspension upgrades to provide increased ground clearance, improve handling and improve the driving experience. 
  • Bodywork to give your ride a unique appearance.
  • Turbochargers and superchargers to enhance your engine’s efficiency by increasing airflow and improving torque.
  • Interiors to add personal elements and make your ride more comfortable. 
  • Paint jobs to conceal scuffs and scratches, increasing resale value.
  • Wheel replacements to decrease your vehicle’s weight, improving fuel economy and handling, and to give your ride a sleek appearance. 

What Does The Law Say?

Although many popular car modifications are perfectly legal, some have the capacity to impact on road safety, making them illegal. There is a great deal of confusion surrounding the legality of car modifications, so it is vitally important you understand the rules regarding specific modifications before you make any commitments. Illegal modifications could result in a fixed penalty notice or a court summons. 

Furthermore, you must notify the DVLA when you make changes to specifications such as your car’s colour, cylinder capacity, engine or number plates, and these factors will affect your registration certificate (V5C). 

What About Insurance?

Every car modification should be declared to your insurance provider, from invasive changes such as engine swaps to seemingly insignificant alterations to your car’s appearance, like stickers. Modifications have the capacity to affect a vehicle’s safety, inevitably affecting the cost of your premium. Due to this price increase, many modified car owners mistakenly keep their alterations undisclosed to their insurance providers. While this may be tempting for the sake of saving a bit of cash, failure to declare modifications (even by accident) could result in your policy being considered invalid, leaving you without cover. If you need to make a claim following an incident, not only will it be refused, but your void insurance could land you with a fixed penalty of £300 and six points on your licence.

Aftermarket Steering Wheels

Aftermarket steering wheels are excellent interior modifications for expressing your personality through your car’s interior. They can also improve your driving experience, offering quicker steering and precision handling. Fortunately, in the UK, there are no specific laws prohibiting aftermarket steering wheels. Provided your steering wheel is safe and functional, and you report it to your insurance provider, you shouldn’t run into any issues. 

Window Tinting

UK law states that window tinting is legal, provided it abides by visible light transmission (VLT) guidelines. Tinted windscreen must let at least 75% of light through to be road legal. Side windows must have a minimum VLT of 70%. If your window tint goes against the law, you may be issued with a ‘prohibition notice’, preventing you from using your vehicle on the road until you amend the issue. 

Underglow Lights

Underglow lights are a common modification; however, if they emit blue or red light, they are classed as illegal, as these colours are reserved solely for emergency vehicles like police cars and ambulances. You may also be stopped by the police or Vehicle and Operator Services Agency if your underglow lights are bright enough to be deemed a distraction to other road users. However, this is largely a matter of discretion. 

Exhaust Modifications

Most exhaust modifications are classed as legal in the UK, provided the sound emitted does not exceed 80dB. Although this varies depending on the vehicle type - for example, HGVs and motorcycles are permitted up to 89dB - you could receive an on-the-spot fine of £50 for exhausts that exceed the legal limit. It is worth noting that in 2026, the legal decibel limit for car exhausts is set to reduce to 68dB.