Insuring a modified car correctly requires declaring every upgrade, choosing the right valuation method, and using a specialist insurer rather than a standard broker. Skip any of these steps and your policy may be invalid at the exact moment you need it most. According to industry data, 1 in 4 modified car insurance claims is reduced or rejected because of undisclosed modifications.

Step 1: List Every Modification

Before you call any insurer, write a complete list of every modification — including ones that seem minor. This includes:

• Engine work: intakes, exhausts, cams, forced induction, fuel systems
• Suspension: coilovers, lowering springs, anti-roll bars, sway bars
• Brakes: big brake kits, braided lines, upgraded pads
• Bodywork: splitters, wings, widebody kits, hood vents
• Interior: roll cage, harness, racing seats, stripped cabin
• Electronics: ECU tunes, standalone maps, launch control

For each modification, note the approximate cost and whether it increases power or changes the car’s risk profile.

Step 2: Get an Agreed Value

Standard car insurance pays market value at claim time — which ignores the £10,000 you spent on a built engine. Specialist modified car insurers offer agreed value policies, where you and the insurer agree the car’s total value (including mods) before the policy starts. At total loss, you receive that exact amount. See our full guide on agreed value vs stated value.

Step 3: Choose a Specialist Insurer

Standard comparison sites like Compare The Market rarely offer true specialist modified car policies. Use a broker or specialist insurer instead. Look for providers who:

• Cover all declared modifications without exclusions
• Offer agreed value cover
• Allow track use (even limited — some offer 12 days per year)
• Have experience with your type of build (drag car, circuit car, show car)

Step 4: Submit Documentation

Good insurers want photos of the modifications, receipts where possible, and a dyno sheet if the car has been tuned. Providing this upfront speeds up the quote process and eliminates disputes at claim time.

Step 5: Review Annually

Every modification you add changes your risk profile. Review your policy whenever you make changes — not just at renewal. Mid-term endorsements are standard practice with specialist insurers and typically cost £25–£50 to process.

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