Does your insurance go up if you modify your car?

As far as insurance is concerned, a modified car is one that has been altered from its factory specifications. Manufacturers tend to make vehicles that appeal to the masses, however, some people want — or need …

As far as insurance is concerned, a modified car is one that has been altered from its factory specifications. Manufacturers tend to make vehicles that appeal to the masses, however, some people want — or need — to make changes to suit their own requirements.

From adding a bumper sticker or tinting the windows to installing a new engine or changing the wheels, there are many ways in which drivers can modify their cars, and there are various reasons for doing so. These reasons can usually be grouped into three categories: Performance, aesthetics, and accessibility.

If you’re considering making some car modifications, it’s important to bear in mind that these alterations may have an impact on your car insurance policy. In this article, we’ll explain the repercussions of modifying your vehicle.

How much will my insurance go up if I modify my car?

Certain modifications, such as adding a bigger exhaust or altering the gearbox, may push up your car insurance premium, but how much is determined on a case-by-case basis.

Other modifications, like installing high-performance brakes or safety devices, could reduce the cost of your insurance, but again the amount it will go down will depend on factors like the value of your vehicle, your driving history and the area you live in.

Continue reading to find out which modifications may increase the price of your insurance and which may lower it.

Why does your insurance go up if you modify your car?

If your insurance goes up as a result of making modifications to your car, it will usually be because of the following reasons:

  • The modifications have increased the value of the car, which means it will be more expensive to repair or replace
  • If the car has been made faster, there’s more risk of an accident
  • A modified car is more attractive to thieves, meaning there’s more risk of it getting stolen

Do I need to let my insurer know if I modify my car?

You should inform your insurance company about any modifications you make to your vehicle — even if you believe your policy won’t be affected by it.

The law states that you must declare any modifications to your insurer, whether you made the changes yourself or not. This even applies to modifications made by the manufacturer. For example, if you choose to upgrade to alloy wheels as an optional extra on a new car. If you buy a secondhand car and you’re unsure about whether it’s been modified, you can take it to a mechanic, and they will be able to tell you.

When reporting modifications to your insurer, it’s important to be as truthful and detailed as possible so they can do an appropriate risk calculation and make any necessary changes.

What happens if you don’t tell your insurance company about modifications?

If you haven’t declared all modifications and need to make a claim, your policy could be invalidated, meaning your insurance provider won’t pay out. Plus, if you’ve had an insurance claim refused or your policy has been cancelled, it will be more difficult and expensive to get cover in the future.

Modifications that are likely to affect car insurance

As mentioned above, some modifications will increase the price of your car insurance, while others will reduce it. Whether or not your premium will increase or reduce depends on your insurer, but to give you an idea, we’ve listed some of the modifications that are likely to have either a positive or negative impact on your policy:

Modifications that may increase your premium

If you’re worried that modifying your car will increase your premium, it’s a good idea to speak to your insurer before making modifications. That way, they can give you a good indication of how your policy will be affected.

The modifications that are most likely to push up your car insurance are:

  • Modifications to the engine and other vehicle mechanics — This can increase your car’s performance, meaning it’s likely to push up your premium. Installing a turbo or supercharger is also likely to increase the price of your policy. Even installing an Engine Control Unit (ECU) to make your car more economical can make your insurance more expensive. So, before you do this, you might want to consider whether fitting one will save you money overall.
  • Installing a short shifter — This makes gear changes quicker, leading to sportier handling, and is associated with younger, riskier drivers.
  • Making your exhaust bigger and louder — Even if you’re fine with upping your insurance before you do so, be aware that removing the silencer is illegal. If it’s missing or broken, you could face a fine. Plus, illegal modifications will invalidate your insurance policy.
  • Upgrading your car’s brake discs and pads — Because some of them are quite expensive, doing this could add value to your vehicle and consequently increase the price of your insurance. Similarly, transmission or gearbox alterations and air filter upgrades can also make your policy more costly.
  • Modifying the wheels — Wheel upgrades are also likely to increase the value of your car, so think twice about fitting alloy wheels or wider tyres.  With this in mind, you may want to check whether your area has a history of alloy theft.
  • Installing body kits — Typically comprised of bumpers, spoilers, side skirts and bonnets, body kits aren’t always made with safety in mind. Sporty bumpers could shatter on the tiniest of impacts, and side skirts can be hazardous on uneven roads.
  • Removing or replacing seats — Your insurer will want to know whether you’ve reupholstered the seats in your car and if so, they may increase your premium.
  • Changes to the steering wheel and pedals — Any modifications you make to the steering wheel and pedals may also increase the price of your car insurance.
  • Cosmetic modifications to the exterior — If your insurance company has had to make large pay-outs for vehicles with custom paint jobs, bumper stickers and decals, under-car neon lights, or custom LED highlights in the past, they may decide to increase your premium.

Modifications that may reduce your premium

The modifications that are most likely to lower your car insurance are:

  • Downsizing the engine — In some cases, car owners choose to downsize their engines to make them more energy efficient. This could mean a cheaper premium.
  • Installing high-performance brakes — This is possible to do on some non-sports cars, and if your car is already highly modified, improving your braking system could significantly reduce the cost of your insurance.
  • Upgrading the suspension — This will usually only lower your premium if your vehicle is heavily modified.
  • Installing a sway bar — Again, this will usually only reduce the cost of your car insurance if you’ve made lots of other modifications.
  • Installing extra safety features — A car modification that increases the security of your vehicle will likely reduce your premium. Devices such as trackers, immobilisers and extra safety locks could reduce the risk of theft.

Modifications that are unlikely to affect car insurance

Even if you’ve made the following modifications and you believe they won’t have an impact on your car insurance, you must still declare them to your provider:

  • Adding a water cooling system — If you choose to improve brake performance with a water cooling system, you won’t usually need to worry about it affecting your insurance.
  • Fitting winter tyres — This shouldn’t increase your insurance because most providers realise that winter tyres help improve the handling of your vehicle in tricky driving conditions. A few years ago, more than 70 insurers signed an agreement saying they wouldn’t increase premiums for declaring them. Winter tyres that are approved by the car manufacturer are even less likely to negatively impact your premium.
  • Cosmetic wheel modifications — In most cases, wheel modifications that aren’t related to performance (novelty hubcaps that spin or light up, for example) won’t affect your insurance, however, this may not be the case if your insurance provider views them as a theft risk.
  • Lowering the suspension — This is unlikely to affect your premium unless your vehicle is already heavily modified or it has affected the vehicle’s handling rather than just being a cosmetic change.
  • Replacing bushings — Swapping rubber bushings for polyurethane ones to suppress vibrations and minimise weight transfer is unlikely to have an impact on the cost of your insurance.
  • Fitting wind deflectors — Because they are usually a manufacturer’s accessory, wind deflectors won’t normally affect your premium.
  • Tinting the windows — Tinted windows won’t increase or decrease your premium, but the law states that at least 75 per cent of light must be able to get through your front windscreen, and 70 per cent must be able to get through the front side windows. If not, your insurance policy could be invalidated.
  • Adding a tow bar — This is also unlikely to affect your insurance.
  • Upgrading your sound system — Doing things like installing a subwoofer to maximise the low frequency of bass sounds is one of the most popular ways to modify your car’s interior, however, unless it’s a high-value system, it’s unlikely to increase the cost of your insurance.
  • Other interior modifications — Dashboard upgrades, replacing the gear knob, changing the panelling, and add-ons like in-built sat-nav systems and car phones probably won’t affect your policy either.

Do I need specialist modified car insurance?

Not all insurers will cover a modified vehicle, so if you are planning on making a lot of car modifications, you may find that you need to buy specialist insurance.

Even if your current provider is happy to cover your modifications, modified car insurance cover could be cheaper, so it’s worth shopping around for quotes. Plus, a specialist insurer is less likely to up your premium if you make bodywork changes, such as installing a body kit (unless the value of the vehicle is dramatically increased).

Modified car insurance covers all the same things that regular car insurance does, as well as the parts and accessories you’ve added. You can also take out all the usual optional extras, for example, breakdown cover, windscreen cover and no-claims discount protection. 

If your modifications have drastically increased the value of your car, you might want to consider buying an agreed-value policy so that if it’s written off, you’ll get more than the market value. It’s also worth noting that a policy with a salvage retention clause will enable you to buy back the remains of your vehicle and its parts.


Modified cars can cost more to insure, but it depends on how they’ve been modified, as some car modifications may reduce the cost of insurance, and others won’t affect the price of a policy at all. Modifications that may increase your premium include changes to the engine and other vehicle mechanics, making your exhaust bigger and louder, upgrading the wheels and installing a body kit. Car modifications like installing high-performance brakes, upgrading the suspension, installing extra safety features and fitting winter tyres are likely to reduce your premium, while insurance providers won’t usually make changes to your policy for modifications like lowering the suspension, tinting the windows and upgrading the sound system.

If you make any modifications to your vehicle, the law states that you must declare them to your insurer so that they can do an appropriate risk calculation and make any necessary changes to your policy. You also need to ensure that all your modifications are legal, otherwise, you risk invalidating your policy.

Also read:
Can you get modified van insurance?
Modified cars – are you driving one and don’t know it?
What types of modifications affect car insurance?