Car Insurance for Modified Cars in the UK

Summary

• You must declare all modifications to your insurer — even small changes like alloy wheels or a new exhaust can invalidate your policy if left undisclosed.
• Performance modifications such as engine tuning and turbo upgrades typically increase premiums by 10–50%, while security modifications can sometimes lower costs.
• Specialist modified car insurers often offer better value than mainstream providers, and honesty about modifications protects you from having claims rejected.

You have fitted new alloys to your car. Looks brilliant. But have you told your insurer? Many UK drivers do not realise that modifications — even cosmetic ones — must be declared. Failing to do so could leave you uninsured when you need cover most.

What Counts As A Car Modification?

A modification is any change to your car from its original factory specification. This includes changes you make yourself and modifications already fitted when you bought the car.

Modifications fall into several categories:

• Performance: Engine remaps, turbo upgrades, exhaust systems, air filters.
• Cosmetic: Body kits, spoilers, custom paint, vinyl wraps, tinted windows.
• Wheels: Alloy wheels, wheel spacers, different tyre sizes.
• Suspension: Lowered springs, coilovers, uprated dampers.
• Interior: Racing seats, aftermarket steering wheels, custom upholstery.
• Security: Alarms, immobilisers, GPS tracking devices.
• Audio: Upgraded stereos, amplifiers, subwoofers.

If it was not fitted by the manufacturer as standard on your specific model, it counts as a modification and must be declared.

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Modifications That Increase Your Premium

Most modifications push insurance costs upward. Insurers view them as increasing risk. Here is how different modifications typically affect premiums:

Modification Type	Typical Premium Increase
Engine remap or chip tuning	30–50%
Turbo or supercharger upgrade	40–60%
Sports exhaust system	10–20%
Body kit or spoiler	15–30%
Aftermarket alloy wheels	5–15%
Lowered suspension	10–25%

Performance modifications cause the biggest increases. An engine remap adding 50 bhp could add hundreds of pounds to your premium. More power often leads to more accidents in the eyes of insurers.

Cosmetic changes also increase costs, though usually less than performance work. Insurers view body kits and custom paint as making your car more attractive to thieves.

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Modifications That Can Lower Premiums

Not all modifications cost you more. Some can actually reduce your premium:

• Thatcham-approved alarms: Can cut premiums by 5–10%.
• Immobilisers: Make your car significantly harder to steal.
• GPS tracking devices: Help recover stolen vehicles quickly.
• Parking sensors: Reduce the chance of minor bump claims.
• Dashcams: Some insurers offer small discounts for fitted dashcams.

Security modifications work because they lower theft risk. The key is choosing modifications that reduce risk rather than increase it. A Thatcham Category 1 alarm could save you money. A loud exhaust will cost you.

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Why You Must Declare All Modifications

Declaring modifications is not optional. It is a legal requirement under your policy terms. Here is what happens if you do not declare them:

Your policy could be voided. Your insurer can refuse to pay any claims. They can also cancel your policy entirely. This leaves you driving without valid insurance.

You could face prosecution. Driving without valid insurance is a criminal offence. It carries six points on your licence and a fine of up to £5,000.

Claims will be rejected. Even if an accident is unrelated to your modifications, your claim can be rejected if you failed to declare changes.

Future insurance becomes expensive. Having a policy cancelled for non-disclosure makes obtaining cover harder and far more costly. You must declare it for years on future applications.

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Getting Cheaper Modified Car Insurance

Modified car insurance costs more, but you can minimise the increase with these strategies:

1. Use specialist insurers. Companies like Adrian Flux and Performance Direct specialise in modified cars and often quote lower than mainstream providers.
2. Join a car club. Some insurers offer discounts to car club members, as membership signals responsible ownership.
3. Fit approved security devices. A Thatcham alarm or tracker can offset premium increases.
4. Increase your voluntary excess. A higher excess lowers premiums, but ensure you can afford it.
5. Limit your annual mileage. Lower mileage means lower risk and lower premiums.
6. Park off-road or in a garage. Secure parking reduces theft risk significantly.

Build your no-claims discount carefully. Years of claim-free driving help offset modification-related increases.

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What To Tell Your Insurer

When declaring modifications, provide complete details:

• The exact name and brand of each modification.
• Whether it is already fitted or you plan to fit it.
• The cost of the modification.
• Who fitted it — a professional garage or DIY.
• Any supporting receipts or documentation.

Be specific. Do not say "it has alloys." State the size, brand, and offset. Do not say "it is remapped." State who did the work and what power increase was achieved.

If you are buying a modified car, get full details from the seller. Run a car history check and verify all modifications before committing. Factor in the higher running costs that come with modified vehicles.

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Before You Modify Your Car

Planning modifications? Check insurance costs first. Contact your insurer or get quotes with the modifications declared before you spend a penny.

Some modifications are not worth it financially. Spending £500 on an exhaust that adds £300 per year to your insurance makes poor financial sense. After two years, you have paid more in insurance than the modification itself cost.

Keep all receipts and documentation for any work done. This proves the modifications were fitted professionally, helps with insurance claims, and adds value if you sell the car. Understanding your insurance policy type is the first step to getting the right cover for a modified vehicle.

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