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Depending on the type of modification, the type of car insurance you have (for example, temporary car insurance, learner driver insurance, third-party or comprehensive), and your insurance company, modifications to your car can increase or decrease your insurance premium. 

What Counts As A Car Modification?

A car modification replaces an existing part with a piece that did not come with the original manufacturer, which changes the appearance or performance of the vehicle.

Depending on what you do, car modifications affect your insurance premium. Although, you can get specialist modified car insurance that will cover any modifications to your car.

Do You Have To Inform Your Insurance Provider Of Modifications Made To Your Car?

You have a legal requirement to declare your modified car to your insurance provider in the UK.

You must declare all known modifications if you buy a modified car and notify your insurer of any changes planned mid policy to be completely covered.

If you plan to make modifications to your car, you may have to get modified car insurance to cover these changes. A modified car insurance policy might also save you money, so it is best to enquire about the modified car insurance cost difference among different insurance providers.

Vehicle modifications you need to declare

Here is a list of modifications that have to be declared to your insurance company, whether you bought the car with them or made them yourself:

  1. Engine and Mechanical Modifications: Any changes to the engine or mechanics of the car (like the exhaust, brakes or transmission) must be declared as these changes will affect your premium.
  2. Wheel Modifications: These changes will make a difference n how the car handles and adds value to the car. You will have to notify the insurance company of these changes.
  3. Bodywork Modifications: Notify your insurance provider if you have made changes to:
    1. The wing or spoiler
    2. The wheel arches
    3. Added any side skirts
    4. Made changes to the exterior lights
    5. Tinted your windows
  4. Suspension and Brake Modifications: If you have improved brakes or changed your suspension, your car performance and handling will be different, and your insurer must be made aware.
  5. Interior Modifications: Some changes to the interior of the car do not have to be declared, but seat changes, changes to the pedals, and altering the steering wheel must be declared.
  6. Adding Stickers and Decals: Several insurance companies consider decals and stickers a modification. Before adding any decorations to the outside of your car, check with your insurer if it will change your insurance costs.

Vehicles Modifications That May Raise The Cost Of Car Insurance Premiums

Certain modifications will increase your car insurance premium.

Custom paint jobs, stickers & decals

Some insurance providers have had to pay a lot for vehicles with decals and stickers, which means these companies will be hesitant to cover these cars under standard car insurance.

Insurers who offer insurance for custom paint jobs and stickewill likely to increase your premium by about 5%. If you are not happy with that, you can always get cheap modified car insurance to cover the changes.

Engine upgrades

Car enthusiasts love to tinker with their engines, but you should know that changes to the car’s engine and mechanics mean that you will have an increased premium.

One example of engine modification that will increase your premium is remapping the Engine Control Unit (ECU). The ECU is responsible for mixing fuel and air in the engine. By changing the ECU to improve performance, you can expect your insurance premium to increase as much as your horsepower.

Cold air intake

When you install a cold air intake, cooler air is fed to the engine, bringing more oxygen and improving combustion in the engine.

This relatively minor modification will only slightly increase your premium.

Upgraded exhaust system

Exhaust upgrades improve the flow of waste through the engine, increasing engine performance and your premium.

Loud exhaust systems are illegal in the UK, and any modifications to the exhaust that makes the car noisier can result in a reaction from the police.

Upgraded brake discs

By installing high-quality brake discs, like carbon-ceramic or slotted brake discs, you are increasing the value of your car, which in turn might increase your premium.

Bodywork modifications

A complete body kit could replace the existing bodywork or be added to the current bodywork, compromising your car’s safety.

Large bumpers and side skirts mean the car has lower clearance and risks getting damaged on bumpy roads.

Here are some additional bodywork modifications that will alter your premium:

If you make any of these modifications, the risk of your premium is increased by 10 to 15%. If you already have modified car insurance, these changes are unlikely to affect your insurance.

Transmission or gear change

A popular transmission mod is short shift kits. These kits decrease the distance between gears, which gives the car a sportier feel. Because these changes can make your car harder to drive, your insurance provider can expect to increase your premium between 5 to 10% for any gearbox modifications.

Replacing or reupholstering your seats

If you improve your seats by upholstering them or having new seats professionally installed, your car value increases, slightly increasing your premium.

On the other hand, if you replace your seat with cheap alternatives that do not comply with safety standards, your insurance premiums will increase by 5 to 10%.

It doesn’t matter why you are making changes to your seats; just make sure to notify your insurance provider.

Alloy wheels

Alloy wheels are stronger than steel wheels and make your car easier to drive. These expensive wheels will increase your car’s value, increasing your premium.

Unfortunately, some areas are infamous for the theft of alloy wheels. If your insurance provider is aware of that, your premiums will be more expensive than if you had steel wheels.

Modified car lights 

Not all modifications of lights will influence your car premiums; in fact, most of them won’t.

Young drivers often fit their cars with LED strips along the bottom of the car. If such a driver has a history of claims, theft and irresponsible driving, then the insurer will consider this and increase the premiums.

Other modifications to lights, such as coloured LED headlights or flashing under-car lights, are illegal and void car insurance.

Lowered car suspension

You are legally allowed to lower your car’s suspension, as long as the steering abilities and angle of the headlights are not detrimentally affected.

However, if your car is lowered, it becomes a hazard on uneven roads and speed bumps, which could increase your premium.

Vehicles modifications that will not affect your car insurance

Most car modifications tend to affect your insurance premium. Still, you can make a few modifications to your car that are unlikely to influence your insurance, especially if you already have modified car insurance. These are modifications that are unlikely to increase your risk of an accident.

Modifications that might invalidate your car insurance

You will invalidate your insurance cover by not declaring any modifications to your car.

There are legal modifications that, when undeclared, will void your insurance policy:

Illegal modifications will also make your insurance policy invalid. These include:

You should always keep your insurance providers up to date if you plan to make any changes to your vehicles.

Are there vehicle modifications that can reduce car insurance premiums?

Downsizing your engine

Smaller engines are more energy-efficient and lighter. These cars are often safer to drive as well. Many car owners opt to switch out the manufacturer’s engine with a lighter, smaller engine that uses less energy. This will decrease your insurance premium.

High-performance brakes

Uprated brakes in non-sports cars will make your car safer to drive. If that is the only modification to your car, it is unlikely to decrease your premium. But, if your car is already highly modified, then better brakes can decrease your premium by 10 to 15%.

Suspension upgrades

An upgraded suspension will improve drivability. Most cars come with standard suspension, so improving the suspension alone will not decrease your premium. Highly modified cars with an upgraded suspension could enjoy a 5% decrease in their premiums.

Sway bars

Sway bars help stabilise the car when it takes tight turns and can reduce the risk of rolling. Installing a sway bar can decrease your premium by 5%.

Water cooling systems

Water cooling systems improve the performance of the brakes, which will decrease the premium of modified cars.

What happens if you don’t declare modifications on your car?

If you do not declare modifications you plan to make, your insurance will be void. It is a legal requirement to declare all modifications, so you commit fraud if you do not declare changes.

Always speak to the insurer first before making modifications, as the insurance company has the right to refuse to insure your vehicle if it has already been modified.

It is illegal in the UK to drive without car insurance – you risk a minimum fine of £300 and a minimum of 6 points on your licence. This would be the best-case scenario. The fine could be much larger, and your car and license could be revoked.

Are Any Car Modifications Illegal?

There is a certain types of modifications that are considered illegal in the UK:


What if my car comes with modifications?

If you get a second-hand car that already has modifications, you can get modified car insurance. But what does modified car insurance cover?

Modified car insurance covers the same risks as any other car insurance policy but is adapted to modified vehicles. This type of insurance will cost more than standard insurance and only cover legal modifications.

Is a dashcam a modification?

Generally, dash cams that can be removed are not considered modifications. However, it differs between insurers. It is best to check with your insurance provider if you plan on installing a dashcam.

Do bucket seats affect insurance?

Changing your seats could increase your premiums if it alters your car’s handling or the car’s safety. Suppose you had fitted in your car bucket seats and were in an accident. In that case, the insurer is unlikely to payout unless they were notified in advance of the seat changes and were satisfied that it met safety requirements.

If I install a tow bar, will that increase my car insurance premium if I install a tow barms?

No, if you install a tow bar, you will be driving slower, reducing your premium by 20%.

Learn more about what affects the price of car insurance to protect those costs associated with driving a car.

Final Thoughts

If you have dreams of modifying your car, always discuss your plans with your insurance company to ensure you will be covered.

If you are buying a modified car, you can get car modifications insurance to rest assured knowing you are protected in case of an accident.

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