UK insurers require you to declare any modification — from alloy wheels to a remap — under your duty to provide accurate information at renewal or when the mod is made. Undeclared mods can lead an insurer to reduce a payout or reject a claim outright under the Consumer Insurance (Disclosure and Representations) Act 2012. Expect premiums to rise for performance mods (remaps, exhausts, induction kits) more than cosmetic ones, and consider a modified-car specialist insurer for heavily modified vehicles.
At a glance
| Modification type | Typical insurance impact |
|---|---|
| Alloy wheels (like-for-like size) | Minimal to small increase |
| Exhaust system upgrade | Small to moderate increase |
| ECU remap / performance tune | Moderate to significant increase |
| Body kit / styling changes | Small to moderate increase |
| Suspension lowering | Moderate increase, may need specialist insurer |
Why disclosure isn't optional
Under the Consumer Insurance (Disclosure and Representations) Act 2012, you must take reasonable care to answer your insurer's questions honestly and completely, including about modifications. If you don't disclose a mod and later claim, the insurer can treat it as a "qualifying misrepresentation" — potentially reducing your payout proportionally, applying different terms retrospectively, or in cases of deliberate non-disclosure, voiding the policy and refusing the claim entirely.
What counts as a modification you must declare
- Engine changes: remaps, turbo upgrades, induction kits, exhaust systems.
- Suspension: lowering springs, coilovers, uprated dampers.
- Cosmetic: body kits, spoilers, window tints beyond standard, wraps.
- Wheels and tyres: non-standard sizes, aftermarket alloys.
- Interior: upgraded stereo/head units with significant value, seats.
- Security additions (trackers, alarms) — these can sometimes reduce premiums, so declare them too.
Why performance mods cost more to insure
Insurers price risk primarily on how a modification changes the likelihood or cost of a claim. A remap or turbo upgrade that raises power output increases both the chance of an accident (more performance, more risk) and the cost of parts and labour to repair, so these tend to move premiums the most. Purely cosmetic changes usually have a smaller effect unless they affect parts value or theft risk.
When to use a specialist modified-car insurer
If your car has multiple significant mods, mainstream insurers may decline to cover it at all, or price it uncompetitively. Specialist insurers that focus on modified and performance cars are often better placed to price the actual risk accurately and may offer agreed-value policies that reflect what you've spent on the build.
Ideally, contact your insurer before carrying out a modification to confirm how it affects your premium and whether they'll continue to cover the car at all. Some insurers require mods to be declared within a set number of days of fitting.
Does the DVLA need to know too?
Separately from insurance, some modifications — such as engine changes, changes to seating capacity, or a change of colour — must also be reported to the DVLA so your V5C registration certificate stays accurate. This is a different requirement from insurance disclosure, and both need to be done.
Common mistakes
- Assuming "it's a small change" doesn't need declaring — insurers decide materiality, not you.
- Forgetting to re-declare mods at renewal, assuming the insurer already knows.
- Buying a car with existing mods and not checking whether the previous owner declared them.
- Not getting written confirmation from the insurer that a mod has been accepted onto the policy.
Frequently asked questions
Do I have to tell my insurer about every car modification?
What happens if I don't declare a modification and then claim?
Do modifications always increase my insurance premium?
Can I get insurance for a heavily modified car?
Do I need to update my V5C after modifying my car?
Sources & further reading
- GOV.UK — vehicle modifications and telling DVLA
- Legislation.gov.uk — Consumer Insurance (Disclosure and Representations) Act 2012
- Citizens Advice — car insurance and your rights
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
