“Has the vehicle been modified in any way?” It’s that vague question when you’re looking for a car insurance quote that can be a real puzzler. Here we unpick what it means.
Even though that question pops up every time you look for an insurance quote, try to find a definitive list of what a specific insurer counts as a modification and you’ll be out of luck. There is no set list for what insurers will count as a modification, but generally this includes any features added to a vehicle after it was manufactured, which can be both physical and software modifications.
This is what a spokesperson for the Association of British Insurers said:
“Insurers generally define car modifications as any features added to your vehicle that were not included when it was originally manufactured. Whether cosmetic or performance-enhancing, you should always tell your insurer or prospective insurer about modifications that have been made or that you are planning to make to your vehicle. Failing to do so could void your policy. If you’re unsure whether something counts as a modification, speak to your insurer or prospective insurer to check.”
Take the small print from Britain’s biggest motor insurer, Admiral. It says that ‘you need to let us know if you have a modification. For example, you need to tell us about modifications like engine remapping’ The sample policy booklet has this: ‘Modifications are any changes to the way the vehicle looks, functions or drives, including any changes to support a disability or relating to your profession or business.’
Understandably, insurers will view some modifications as increasing the risk of theft, the car being involved in a speed-related accident, or having its handling affected.
Options on new cars don’t count
In case you were wondering, ‘modified’ does not apply to options fitted to the car when it was new, because they were fitted by the manufacturer, not you. If you’re ordering your next new car and having fun with the online configurator, there’s usually a choice of expensive extras. A different colour paint option can easily cost over £1,000 even on a modest car like the new Renault 5 E-Tech. Fancier alloy wheels on something like a BMW go over £2,000 a set. However, you may need to declare factory-fitted options if they enhance your vehicle’s performance, as this could impact your vehicle’s risk profile.
Incidentally, if you have upped the invoice price on your new car, or if you’re concerned about how much you would lose if it gets stolen by getting a ‘market value’ settlement, you may want to consider gap insurance.
So, whether you already own a modified car, are thinking of buying one, modifying the one you have or just don’t want to get caught out by not knowing that it’s been modified, what kinds of modifications fall into the ‘tell your insurer’ category?
Performance modifications and insurance
Changing the engine to produce more power – usually by a software update, otherwise called re-mapping – is likely to set the biggest alarm bell ringing for your insurer, as they will view it practically as a different car. It’s simple to do. For example, the long-established Mountune company (approved by major manufacturers) offers a software update to the Mk7/Mk7.5 Volkswagen Golf GTI to raise its power from 220hp to 310hp, which an owner can achieve themselves using their smartphone and a Bluetooth adaptor.
Upgrading an exhaust system can also increase power and is a popular mod. An aftermarket exhaust removes restrictions which allow exhaust gasses to escape more easily which in turn allows air and fuel to be drawn into the engine more effectively. And yes, they make a lot more noise.
There are modifications which won’t make a car any faster but will change the way it drives. To take a niche example, many owners of Alpine A110 sports cars have a (reversible) modification to the suspension geometry advised by a UK specialist, highly regarded by enthusiasts and the press (and tacitly by the manufacturer) and/or different suspension springs.
As an aside, the car valuation specialist Cap HPI warns owners that when it comes to selling, extreme engine modifications, such as ECU remaps or larger turbos to increase the bhp output, can raise concerns about potential reliability issues and even maintenance costs. Similarly, unauthorised or non-original aftermarket parts can reduce the vehicle’s value due to potential risks and warranty issues.
Cosmetic modifications and insurance
Cosmetic car modifications include stripes, body kits, sunroof installation, tinted windows, specialised paintwork and speaker systems. Adding bigger wheels and shiny alloys can be perceived as affecting handling and make your car a target for thieves.
On the other hand, the added privacy of tinted windows (legal standards apply to windscreen and front window tints) can even be considered a crime deterrent by some insurance providers because it’s hard to see what’s on the back seat.
What you might call practical modifications such as adding rear parking sensors to an older car which didn’t have them from new, or driving aids for a disability, should be notified but shouldn’t affect the premium. Parking sensors or an extra alarm demonstrate a thoughtful owner. Driving aids are essential for some people and, in any case, Motability cars come with inclusive insurance.
Modified car insurance
If your usual insurer comes up with a sky-high premium for the mods to your car, there are specialised companies who deal in modified cars. The comparison site Compare The Market has a specific section for modified car insurance and as of April 2025, offers 187 provider products connected with modified car insurance.
Modified car insurance will cost more, but you’ll know you’ll be covered. You still need to make sure the changes are legal. If you have a car that’s carrying a lot of expensive changes, an agreed-value policy will give you a set value for your vehicle, rather than the average market value.
Taking issue with your insurer
If you have a complaint about your car insurer, there’s somebody to take it up with. The Financial Ombudsman Service deals with complaints between financial businesses and their customers which includes home, car, travel and other types of insurance. Its service is free for consumers, and complaints about car insurance are a steady trade, although there is no specific data on numbers.
The Service says that ‘We’re seeing cases where car owners had to pay a significant amount of money because they unknowingly invalidated their insurance after modifying their car. We’ve also seen cases where car owners told their insurer about the modifications and paid more for their insurance. But when they made a claim, they discovered that the value of the modification isn’t covered.’
It warns that on cosmetic modifications, ‘often, drivers are unaware that simple modifications, like tinted windows or changing alloy wheels, can lead to higher premiums due to the increased risk associated with those vehicles.’
It seems alloy wheels can be a grey area, because somebody buying a car may not know that non-standard wheels have been fitted then have an insurance claim refused. On its website, the Financial Ombudsman Service gives an example of a consumer who filed a complaint after his motor insurer voided his policy and declined his claim following an accident.
When the insurer looked at the claim, they discovered the car had alloy wheels fitted that were three inches larger that the manufacturer’s standard size. The consumer claimed he did not know the wheels had been modified.
The Financial Ombudsman Service felt that an average consumer would not spot the difference in the new and standard tyres. It believed the consumer took reasonable care when applying for motor insurance, ordered the insurer to reinstate the policy and take several other steps to put things right, including compensating the consumer for distress and inconvenience.
The Ombudsman also gives an example of a complainant who had their insurance voided when the insurer found out that a non-standard air filter had been fitted and declared it to be a modification. The Ombudsman felt that the replacement air filter had a negligible impact on the performance of the car – and on the likelihood of it being stolen or damaged – and ruled in favour of the owner.
In another case which went in the insurer’s way, a consumer made a claim after an accident, only to have his policy voided when the insurer learned about an undeclared ECU remap and exhaust retuning. The consumer argued that these modifications were already in place when he purchased the car.
Despite this, the insurer produced evidence that he was aware of the modifications and had failed to disclose them. The Ombudsman agreed that the insurer’s decision to void the policy was fair and in line with legislation.
It’s especially important to establish if a car you’re buying has been modified, although with engine remaps, this is usually advertised as it’s a positive selling point to some buyers. If you’re not sure, ask questions and make sure you have any paperwork to go with the mods.
Leased car modifications
Most privately leased cars do not come with insurance cover, and a whole set of rules apply to modifying a lease car because you don’t own it, the leasing company does.
What you are permitted to have done all depends on the individual leasing company, but these companies will often allow changes if they are not going to leave any lasting damage or marks on the car when you return it. They have to be fully reversible.
That includes cosmetic changes such as adding alloy wheels (larger than the original spec), performance changes like remapping the car’s engine, and usage changes such as adding a towbar or roof rack.
At the end of a lease, any residual damage to the car once the changes have been reversed is assessed according to an agreed set of criteria from the British Vehicle Rental and Leasing Association (BVRLA). If you are leasing a vehicle, you should request a copy of the BVRLA Fair Wear & Tear Standard from your leasing company directly. The only reference to performance mods in the guidance is that you need permission.
If you don’t tell the leasing company or your insurer about a modification and you have an accident, you’re doubly liable. The registered keeper is liable to pay the outstanding balance to the finance company if the car is written off as the insurance policy would be void.
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