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Modified Car Insurance

Compare insurance quotes for modified cars

Custom changes to your car can increase the cost of your car insurance. Before you get revved up, read our guide to insuring modified cars

By Tim Heming

Published: 23 September 2021

Bonnet of a car with air intake and go faster stripes

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What car insurance do I need for a modified car?

While the usual types of car insurance policy apply, your car insurance premiums must be based on any modifications that have been made on the vehicle. This is why if you do make any custom changes – or you purchase a vehicle that has been customised from the factory model – you should let your insurance provider know. 

Failure to do so could result in your policy being invalid when you come to make a claim.

How does modified car insurance work?

If you have your heart set on modifying your car, then you should always consult your insurance company before you do anything. They can tell you what impact, if any, the changes will make to your policy and premiums. You can then weigh up whether any modifications are worth the increase in insurance costs.

Insurers allocate each car to one of 50 car insurance groups (one is the cheapest and 50 the most expensive). If the specifications of your car have changed, the vehicle no longer conforms to their analysis, and the rating is void. It must therefore be placed under a modified car insurance group, which is likely to be more expensive than its original rating.

Insurers’ logic is that modification work done on the structure or mechanics of a car outside the factory cannot be guaranteed, and that it might compromise the integrity of the vehicle.

Always be honest about any modifications you are planning to make or have already made. It could be tempting not to disclose them, but if you aren’t up-front, you risk invalidating your policy completely.

What counts as a car modification? 

Any change that makes the vehicle different to when it left the factory counts as a modification and could affect the price of your premium, sometimes increasing it substantially. 

What are the most popular types of car modification?

The most popular car modifications in the UK are alloy wheels, tow bars and parking sensors. Other common customisations include change of engine, suspension and full body kit.

Modifications such as personalised number plates may not directly affect your car insurance premium, but you will need to notify your insurer if you make them, and an admin fee may be charged to update your records.

The most popular car manufacturers to modify are Subaru, MG, Rover, Jeep and Land Rover.

How much does it cost to insure a modified car?

The cost of insuring a modified car will depend on various factors such as the type of modification, the age of the driver, where the car will be kept and how many miles it will clock up. While modifications will differ between vehicles, our data show that the price for annual car insurance is £12 higher on average for a customised car, rising from £616 to £628.*

*Based on fully comprehensive policies with one driver holding a full UK licence. MoneySuperMarket data collected between January and June 2021.

Why are modified cars more expensive to insure?

The main reason why your insurance premiums could go up is increased risk.

Insurance companies calculate their prices using statistics, and because motorists using high-performance vehicles are more likely to be involved in a crash – and many modifications improve a vehicle’s performance – insurers believe their premiums should be higher. 

Modifying your vehicle introduces an element of uncertainty because the insurer is not 100% sure of the workmanship or what specifically has been done. They mitigate this uncertainty by putting up the cost of cover. 

Modified vehicles are also often more attractive to thieves, and are therefore at greater risk of being stolen, which also increases your premium.

Car modifications don’t have to be significant to have an effect on your insurance and include entertainment systems and parking sensors.

Modification Category

Average annual premiums*

No modifications








Suspension and steering








Body modifications


*Based on fully comprehensive policies with one driver holding a full UK licence. MoneySuperMarket data collected between January and June 2021.

Does modified car insurance cost more for younger drivers?

You are likely to see the biggest increase in the price of premiums if you modify your car as a younger driver. Already considered high-risk by insurers, young drivers on average tend to have more accidents than older, more experienced drivers.

According to the Association of British Insurers (ABI), younger drivers are now spending more than 10% of their annual salary on car insurance. For this age group, modified car insurance prices will be particularly expensive and may even become unaffordable.

What modifications can lower the cost of car insurance?  

Not all modifications push up car insurance premiums. If you install additional security measures to prevent your car from being stolen, such as an alarm, you may see your premiums fall because your provider considers you a lower risk.

The same holds true for immobilisers and tracking devices, but call your insurer to check whether a reduction will be made and how much it will be.

Can you add modifications to your car mid policy term?

You can customise your vehicle whenever you choose, but you must notify your insurance company who will then make a decision on how the modifications affect your premiums. 

The important thing to understand is that the existing insurance policy covers your car for its original condition. Once that is changed, the policy needs to be adjusted to suit or you risk invalidating the insurance.

What does modified car insurance cover?

The range of insurance available for a modified car is the same as for any other vehicle. This includes fully comprehensive, third-party, fire and theft, and third-party only. You can find out more about the different types of policies with our guide.

How can I reduce the cost of modified car insurance? 

Whether you make modifications to your car or not, shopping around to find the best value car insurance is a good idea. You can compare modified car insurance quotes at MoneySuperMarket.

Bear in mind that as well as comparing different quotes, there are other things you can do to try and reduce the cost of cover. 

  • Consider raising the excess on your policy to keep premiums down. This is the portion of any insurance claim you must pay yourself. However, make sure the excess remains affordable
  • If you’re a younger driver, you may be able to reduce the cost of cover by adding an older, more experienced driver to your policy. But make sure not to name them as the main driver on the policy, which could invalidate your insurance altogether. It could also lead to penalty points on your licence as well as a potential fine
  • Finally, try to pay for your cover upfront rather than in monthly payments. Insurers usually impose high interest charges if you opt to pay monthly rather than annually

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