Which car modifications do I have to tell my insurer about?

The word modification suggests something deliberate and sporting, which is why so many go undeclared. Insurers define it far more broadly: anything that makes the car different from how the manufacturer built it. A previous owner's alloy wheels count. A tow bar counts. A roof rack that stays on counts. The test is not whether it makes the car faster, but whether it changes the risk — of a claim happening, of the claim being larger, or of the car being stolen.

Safety

Step by step

1. Start from the manufacturer's standard specification, not from what the car looked like when you bought it.You are responsible for the car as it is, not for who changed it. A modification fitted by a previous owner is still a modification, and 'it was like that when I bought it' is not a defence. This is a good reason to ask specifically when buying used.
2. Declare anything affecting performance.Engine remapping or chipping, exhaust changes, induction kits, turbo or supercharger changes, transmission changes. These are the category insurers treat most seriously, because they change how the car behaves and who is attracted to driving it.
3. Declare wheels, tyres and suspension changes.Non-standard alloy wheels, larger diameters, lowered or raised suspension, coilovers, uprated brakes. These affect handling, the cost of repair, and theft appeal. Wheels in particular are among the most commonly undeclared modifications.
4. Declare cosmetic and bodywork changes.Body kits, spoilers, respray in a non-standard colour, tinted windows, wraps, non-standard lighting. Cosmetic changes do not affect how the car drives but they do affect the repair cost and, in some cases, whether the vehicle complies with construction and use requirements.
5. Declare towing and load equipment.A tow bar, roof bars, a roof box left fitted, a bike carrier, a van racking system. A tow bar is a genuine surprise to most people. Insurers vary on whether it affects the price and many do not increase it, but it is a change from standard and it should be recorded — not least because it affects what happens if the car is damaged while towing.
6. Declare security devices, even though they usually help.An alarm, an immobiliser, a tracker or a steering lock is a modification too. These commonly reduce a premium rather than raise it, particularly a Thatcham-recognised device, and some insurers require one on higher-value vehicles.
7. Declare disability adaptations.Hand controls, a left-foot accelerator, a wheelchair hoist, a swivel seat. These must be declared as changes from standard. They should not be treated as an increased risk in themselves, and if you feel a decision on an adaptation is unfair, that is a complaint the Financial Ombudsman Service can look at.
8. Declare anything permanently installed for technology.A hardwired dashcam, an aftermarket infotainment head unit, a rear camera, a permanently fitted phone mount that required drilling. Whether the insurer cares varies, but the principle is the same.
9. Ask for the record in writing.After declaring, check that the modifications appear on the amended schedule or statement of fact. A telephone declaration the insurer has no note of is worth nothing at claim time, and this is the single most common failure point.

Tips

• Ask the question in this form: 'the car differs from standard in the following ways — please confirm which of these you need recorded and whether any of them change the terms'. It puts the classification decision where it belongs.
• Check whether the policy covers the modified parts themselves. Some policies cover the vehicle as standard and exclude the value of non-standard parts unless they are specifically listed.
• When buying a used car, ask the seller directly what has been changed and get it in writing on the receipt. The MOT history and the V5C will show a colour change or a recorded engine change, but not much else.

Common mistakes

• Assuming a modification only counts if it makes the car faster — Insurers define it as any departure from the manufacturer's specification, including cosmetic and functional changes that make no difference to performance.
• Not declaring something fitted by a previous owner — You insure the car as it is. Who fitted it is irrelevant to whether it must be declared.
• Declaring by phone and never checking the paperwork — The schedule and statement of fact are the record. If the modification is not on them, it was effectively never declared.

Questions people ask