Modified Car Insurance: The Complete Guide

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Are you thinking of modding your car? Looking to buy a custom car? Or maybe you already have a modified car and it’s time to renew your insurance? Whatever your situation, this one-stop modified car insurance super-guide will tell you everything you need to know.

What is modified car insurance?

Modified car insurance is designed for any vehicle that has had changes made to its factory specifications. This could be for cosmetic reasons or to improve performance. Any vehicle adapted to meet the access and disability needs of the driver or passengers is also considered modified.

Why do I need specialist modified or custom car insurance? Isn’t normal insurance enough?

Insurance premiums are calculated using a complex algorithm that identifies risk. Standard insurance won’t cover any modified vehicles because these special cars normally cost more to put right than an unmodified vehicle in the event of a claim. They may also make your vehicle more of a target for thieves. Some modifications to bodywork or performance can also affect the handling of your vehicle. And that could put you at higher risk of making a claim.

1. Know the three essentials for getting a good deal 

#1. Get a deal that’s exactly what you need.

It may sound obvious, but not all modified car insurance will cover you for the same things. Don’t just opt for the cheap car insurance deals- make sure you have the cover you need by ensuring any car insurance quotes cover you for the following, if you need it:

  • Track day cover
  • European cover
  • Like for like cover on all modified parts
  • Remember that if you’re under 21, you may end up paying more –  insurance companies see young drivers as a higher risk of making a claim


Drive the best car insurance deal, without compromising on your level of cover by looking for a tailored insurance package. That way you only pay for what you need.

#2. Don’t rely on price comparison websites.

Car insurance comparison sites won’t be able to cover your specialist car needs, so get ready to ring around or use an expert broker to do the legwork for you. An independent broker will be free to look for and compare the best value car insurance out there. Some will have preferred broker status with some of the UK’s leading insurance firms, so are able to negotiate a great price on your behalf.

#3. Check if the following opportunities for discounts apply to you

  • Limited mileage. If you don’t use your modified car every day or for long distances. Beware of under-estimating though as you could find your insurance is invalidated if you seriously exceed any limit. This handy online mileage calculator can help you work out how many miles you’re likely to cover each year.
  • For 17 year olds in particular, modified car insurance can be pretty steep but taking (and passing!) a Pass Plus exam may help reduce premiums
  • Second car. Most modified car owners also own another vehicle. Make sure you mention this to take advantage of second car discounts
  • Car club or owners club members. If you’re a member of a car club or owners club you could be entitled to extra discounts on your insurance. Find out more about clubs at:

2. Speak to a broker before buying a modified car

Look for your ideal second hand modified car at dedicated car sites like pistonheads, but make sure you check out the likely insurance costs before you commit.

Do it today:

If you’re thinking of buying or modifying your car, contact an insurance broker for a modified car insurance quote and check the likely insurance costs upfront, to make sure you’re happy before you make the purchase.


3. Get guidance if you’re making the modifications yourself

If you’re looking to buy parts and body kits try madmotors, or scoobyworld if you’re a Subaru fan. For ideas and support, hang out with some experts at a modified card forum.

Do it today:

You need to make sure your insurance company is aware of all modifications or you could invalidate your insurance. Driving without insurance can have serious consequences.

4. Stay within the law – know what modifications are legal (and what are not)



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Devon and Cornwall Police may have raised a smile by suggesting that Back to the Future-esque flux capacitors. But seriously, you do need to make sure that any modifications you make don’t leave you on the wrong side of the law.

Do it today

You need to check the modifications are acceptable under the Road Traffic Act – read the section on construction and use of vehicles.

Stretched tyres

Fitting stretched tyres is illegal and it can negatively affect the handling and safety of your vehicle. Fitting this type of tyre contravenes the Type Approval of the vehicle and renders it not fit for purpose. This could lead to prosecution for dangerous condition of the vehicle.

Upgrades to brakes

Upgrading to bigger brake callipers is a common modification, and a prudent move if you’ve upped your car’s performance. But it’s wise to check with your vehicle manufacturer that your intended choice is suitable. It’s also sensible to use a professional to ensure they are correctly fitted so you stay safe. The Good Garage Scheme can help you find a reputable garage.

Number plates

Number plates must be white reflective to the front and yellow reflective to the rear and the characters have to be black. The exception to this rule is if the vehicle is registered prior to 31 December 1972, in which case black and silver number plates can be fitted front and rear.

It is illegal to change the size, spacing, format, font or characters of a number plate, and only the national identifiers relevant to the United Kingdom or home nations (England, Scotland, Wales or Northern Ireland) may be displayed.

If your number plate does not comply with the relevant legislation, you could be fined up to £1,000 and your car will fail its MOT test.

Do it today:

Read the full government guidance on number plate display


How noisy is too noisy?


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Playing loud music in your car can be considered to affect the way you drive. To try to improve road safety, the police have various powers if they feel the volume is too high.

  • ASBOs– Local police forces are entitled to serve ASBOs banning drivers from certain roads under the Police Reform Act 2002
  • Seizing a vehicle – Under the same act, the Police can stop and seize a vehicle which is causing alarm, distress or annoyance to members of the public
  • Confiscating equipment – Under the Environmental Protection Act 1990, loud music from stationary vehicles may be defined as a statutory nuisance, which allows Environmental Health Officers to serve abatement notices, impose fines or confiscate the audio equipment


Spoilers look sporty and play a huge role improving handling at high speed. But common sense says it must not impair your vision in any way and make sure it does not have sharp edges.


Installing undercar neon lights is popular, but it’s illegal if the tubing is on show. It’s also important that the lights are not considered too bright and a distraction to other road users. If you want to modify your headlights or fog lights, all front facing lamps must glow white or yellow by law. And rear lights should always be red. Other colours are not permitted. The law states that only emergency vehicles can display blue lights.

Do it today:

Stay on the right side of the law by checking out the rules about lights on vehicles 

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One of the most frequent questions that people ask us is, “what can I do to keep my insurance costs downs?” But sometimes, the more pertinent question to ask, “What are the current factors that are driving up the cost of my car insurance?”

5. Check the Top Ten alterations that will inflate your modified car insurance premium

We’ve created a list of the top 10 modifications that will affect car insurance quotes. It’s been compiled using analysis of 2.3 million modified vehicles in the UK produced by Using this data, we’ve also calculated the average amount that each type of modification will increase your car insurance costs by.

#1. Turbo/super-charging/ nitrous oxide (132% increase)

It should come as no surprise that the modifications that can have the greatest impact on car insurance costs are the ones that are intended purely to increase the power output of the engine, the acceleration and vehicle top speed. This is because the faster that you go and the harder you accelerate, the more likely you are to potentially be involved in a road accident.

Insurance companies generally perceive motorists who drive cars with these modifications to more actively engage in risky activities such as speeding and frequent overtaking. For these reasons, adding a turbo, supercharger or nitrous oxide to your vehicle may more than double the price of your car insurance policy.

Do it today:

#2. Wheelchair clamps, lifts, straps and winches (69% increase)

At the opposite end of the spectrum, making a vehicle wheelchair accessible can also have a major impact on the cost of insurance. Though it may seem initially unfair that those in wheelchairs or who transport people with mobility problems should have to pay higher insurance premiums, there is some sense in this. By modifying the vehicle to be wheelchair accessible you are effectively increasing its value substantially, and so the cost of insuring it will also rise correspondingly.

In addition to this, in the event of an accident the vehicle will cost more to repair because of its specialist adaptations, so increasing the payout cost of the insurer.


Do it today:

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#3. Bonnet ‘bulges’, flared wings and wheel arches (66% increase)

While bonnet bulges, flared wings and similar parts may seem like purely cosmetic modifications, they are also structural modifications which may affect the aerodynamics and thus handling of the vehicle. On top of this, the insurance company has no guarantees that such modifications have been carried by a reliable mechanic or fitter, and how safe and secure they are, so they are seen as an increased risk.

Such parts can also add significantly to the overall value of the car, the cost of repairing it, and to the likelihood of it being stolen.

Do it today:

 #4. Modifications to transmission or gears (63% increase)

Gear and transmission modifications are also frequently performance enhancements, which will affect the acceleration capabilities and overall top speed of the vehicle. This again will increase the risk of an accident occurring, and the types of drivers who fit such modifications are generally perceived by the insurance companies as being more prone to engaging in risky driving behaviours, which might result in an accident.

Do it today:

  • Improve your gearbox and transmission with racing and performance kits

#5. Hand controls (57% increase)

While many of the modifications discussed here are purely cosmetic or performance-related enhancements, which are in no way ‘necessary’ to the vehicle or its driver, some modifications come from necessity. For drivers who have limited use of their legs or feet, the adaption of the vehicle to have hand controls for acceleration and braking is one such modification.

The reason for the increase in insurance cost for vehicles with hand controls is not because they are perceived as being more difficult to use or more likely to result in an accident. Instead, it’s because of the substantially increased cost of repairing or replacing the car and its hand control system in the event of a claim. Because the standard payout for the vehicle at the normal market value would not cover the cost of these repairs, the cost of the policy is greater to account for this.

Do it today:

#6. Complete body kit and panels (57% increase)

Although often sold and fitted as one complete kit, body kits are in fact a collection of modifications comprising a number of different exterior parts. Hardly surprising then that they can increase the cost of your insurance premium by more than half. Body kits usually consist of cosmetic enhancements such a spoilers, front and rear bumpers, skirts, guards and scoops, while panels made of fibreglass and other materials are also frequently used to modify the appearance of the vehicle.

A car fitted with a body kit will cost more when it comes to insurance for a number of reasons. Firstly, the often substantial cost of the body kit itself increases the value of the car, and so the cost of an insurance pay-out in the event of a claim. Secondly, it may increase the attractiveness of the car to thieves, adding substantially to the risk of claim being made on the policy. Thirdly, though predominantly cosmetic, the substantive nature of the modification may significantly affect the handling and aerodynamics of the vehicle. And the potential for improperly fitted parts may also increase the risk of claims made by third parties struck by parts that come loose.

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#7. Roll bars/ roll cages/ seat removal (41% increase)

You could argue that roll cages and bars are designed to make the vehicle safer and protect its occupants in the event of a crash. But the fact is that their main association is with racing (particularly rally racing). Put simply, when insurers find that you have fitted these, they will often question your assertion that you are only going to use it for going to work and the shops. In addition to the perception that the car may be used in risky situations such as racing, the value of the equipment will also push the overall value of the vehicle up.

While most of the modifications discussed here involve the addition of parts to the car, when removing key parts you should also notify your insurance company. There are a number of reasons why you might remove one or car seats. This could include to allow more space for transporting cargo, or reducing the weight of your car if you use it for track days. Whatever the reason, it is vital that you tell your insurance company, as you are significantly changing the vehicle from its original state – ie there will be a different number of passengers, therefore a different quantity of risk.

Do it today:

  • Look for a roll cage supplier who complies with MSAUK regulations

#8. Uprated brakes (36% increase)

Brakes are amongst a car’s most critical parts, so modifying them will affect your insurer’s assessment of risk. ‘Uprated brakes’ are high-performance brakes which deliver more stopping power. You could argue that better brakes are safer and therefore less of a risk, but it’s not the way insurers see it.

One of the most common reasons for upgrading brakes is when the power output or acceleration of the car has been upgraded. More power and faster road speeds require a greater amount of stopping power to slow down or stop. Driving at faster speeds is associated with a greater amount of risk, and so results in a higher insurance premium. Even if no other performance modifications have been made, when uprated brakes have been installed insurers will generally assume the driver will think that s/he can drive faster and stop quicker.

The key point is that modifying an integral part of the vehicle substantially changes the way it behaves. And the risks associated with it therefore it must be reassessed.

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#9. Specialised paint work (36% increase)

A new paint job might seem like a pretty innocuous modification that hardly warrants attention. But this too is something that you need to inform your insurance company about. Specialist paint work like intricate designs or colour shifting paint can radically alter a vehicle’s look and increase its value. To insurance companies, this translates as a higher risk of theft and of them having to pay out.

If you don’t inform your insurance company about specialist paint work, you will not be covered for it. Even if your policy is not completely voided, it will only cover the cost of a factory standard paint job.

Do it today:

#10. Non-standard engine change or tuning (29% increase)

The engine of your vehicle is undoubtedly one of the biggest factors that will affect how much insurance you pay. A ‘non-standard’ engine will inevitably result in a non-standard insurance risk and a corresponding increase in the policy cost.

When insurance companies calculate insurance costs for a make and model of vehicle (without considering the driver or any other factors), they assess the vehicle as a package. Cars are produced in factories to be identical to those with the same model number, so they present a standard amount of risk across the many thousands that are produced. However if you replace the engine with one that is not found in that in post-factory package, or otherwise tune your engine to alter its performance, they must reassess the amount of risk that it poses is a special case.

Do it today:

Modified car insurance essentials:


  • Look for an insurance package that is as unique as your car. Speak to an expert rather than relying  on ‘instant car insurance quotes’ or generic car insurance comparison websites
  • Check the insurance repercussions before you make changes. You may be surprised at the difference a seemingly small modification can make
  • Make sure you tell your insurance company as soon as you make any modifications to your car
  • Remember that any improvements to your car can make it more attractive to thieves – this will affect your insurance premium
  • Make sure that modifications are carried out, wherever possible, by authorised and reputable dealers or using official standard materials
  • Know where there are opportunities for discounts on modified car insurance, and make the most of them
  • Speak to an expert