Any modification that changes your car from its manufacturer's original specification must be declared to your insurer. This includes performance upgrades (engine, exhaust, suspension), cosmetic changes (body kits, tints, wraps), and tech additions (aftermarket stereos, dash cams hardwired in). Failing to declare a modification is material non-disclosure — insurers can and do void policies or reduce payouts when undisclosed mods are discovered at claim time. Declaring mods honestly often adds less to the premium than you fear.
Modifications: what must be declared
| Modification type | Must declare? | Typical premium impact | Examples |
|---|---|---|---|
| Performance engine / ECU tune | Yes — always | High (+15–50%) | Remapped ECU, turbo upgrade, cold air intake |
| Suspension / lowering | Yes | Medium (+5–20%) | Coilovers, lowering springs, strut braces |
| Exhaust system | Yes | Low–Medium (+5–15%) | Cat-back, headers, aftermarket silencer |
| Wheels and tyres (non-standard size) | Yes | Low–Medium | Upsized alloys, plus-size tyres |
| Body kit / aero | Yes | Low–Medium (+5–15%) | Splitter, spoiler, wide arch kit |
| Window tints | Yes in most cases | Low | Especially if below legal VLT limits |
| Cosmetic wraps / paint | Yes | Low | Full or partial colour change |
| Safety additions | Usually yes, but may reduce premium | Neutral to positive | Upgraded brakes, roll cage, fire suppression |
| Dashcam (hardwired) | Yes | Low / neutral | Wired to fuse box |
| Standard accessories (soft furnishings) | Typically no | None | Floor mats, sunshades |
Why you must declare modifications
Insurance is a contract of utmost good faith (uberrimae fidei). You are legally obliged to disclose any material fact that would affect the insurer's decision to cover you and at what price. A modification that changes the vehicle's performance, value, risk profile or repairability is a material fact. Withholding it is misrepresentation.
The practical consequences at claim time are severe. Insurers that discover an undisclosed modification can:
- Void the policy entirely from the start — leaving you without any cover for the claim.
- Reduce the payout proportionately (the 'average' clause) to reflect the premium difference between what you paid and what you should have paid.
- Decline the specific claim if the modification is directly related to the loss.
- Cancel the policy going forward — making future insurance harder to obtain.
Performance modifications: the highest-risk category
Engine remaps, forced induction upgrades (turbo, supercharger), and power-increasing exhaust or intake modifications are the category insurers take most seriously. They increase vehicle speed capability, alter the power-to-grip balance, and directly affect accident severity. Premium loadings for significant power upgrades can be 20–50% on top of standard rates.
Remapped ECUs deserve special attention: they are invisible to a quick visual inspection, making it tempting not to declare them. They are, however, often detectable via OBD diagnostic tools during an engineer's post-accident examination — exactly the kind of check an insurer commissions when investigating a high-speed accident claim.
Cosmetic and appearance modifications
Body kits, wide arches, spoilers, vinyl wraps and colour changes are often seen as lower-risk by insurers — but they still must be declared for two reasons. First, they change the vehicle's description, meaning the insurer has not agreed to cover the car as it actually exists. Second, some body modifications (widened arches, lowered ride height) affect insurance-relevant handling characteristics.
In the UK, windscreen VLT (visible light transmission) must be at least 75%; front side windows at least 70%. In the US, limits vary by state. Tinting below the legal limit is not just an insurance declaration issue — it is illegal to drive and can result in an MOT fail (UK) or roadside citation (US). Insurers may refuse to cover a claim on a car with illegal modifications. Declare even legal tints.
Safety modifications: declare these too, but expect better news
Modifications that demonstrably reduce risk — uprated brakes from a reputable manufacturer, fire extinguisher systems, roll cages, better-rated harnesses — may actually reduce your premium or be viewed neutrally by specialist insurers. Declare them: the outcome is more likely to be positive than negative, and you ensure the insurer's record accurately reflects what they are covering.
How to insure a modified car
If your modifications are significant, mainstream insurers may decline or apply heavy loadings. The specialist modified car insurance market (Adrian Flux, Footman James, Norwich Union specialist arm, Accelerate in the UK; Heacock Classic, American Collectors in the US) exists for exactly this situation and has underwriting expertise with modified vehicles. Practical steps:
- List every modification when requesting a quote — no omissions.
- Get the car professionally valued or appraised if modifications have increased its value significantly.
- Consider a specialist insurer who understands the modified market; they will usually price more accurately than a mainstream insurer who simply loads a high percentage.
- Keep receipts and documentation for all modifications — useful for agreed value and for demonstrating quality of parts and installation.
- Inform your insurer of any new modification mid-term, not only at renewal.
India: modifications and IRDAI rules
In India, modifications to a vehicle are governed by the Central Motor Vehicles Rules. Structural modifications require prior approval from the Regional Transport Office (RTO). Modifications carried out without RTO approval make the vehicle technically non-compliant with the Motor Vehicles Act, which can affect the validity of insurance claims. IRDAI requires insurers to be informed of modifications that change the vehicle's IDV. Performance modifications that increase the vehicle's value should be reflected in a higher IDV at renewal.
Frequently asked questions
What happens if I don't declare a modification and have an accident?
Do I need to declare a dashcam?
Does a vehicle wrap need to be declared?
Can I get agreed value insurance for a heavily modified car?
Do modifications void my car's manufacturer warranty?
Sources & further reading
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.
