Modifying your car can improve its appearance, performance or driving experience. From upgraded suspension and alloy wheels to engine tuning and body kits, modifications allow owners to personalise their vehicles. However, modifications can also affect your insurance, resale value and even whether your car remains road legal.
If you’re planning to modify your vehicle—or you’re thinking about selling a modified car—here’s everything you need to know.
If you’re ready to sell, you can also visit our valuation guidance hub for guidance on valuations, selling options and preparing your vehicle for sale.
What counts as a car modification?
A car modification is any change made to a vehicle that differs from the manufacturer’s original specification. According to the RAC, modifications generally fall into two categories: cosmetic upgrades and performance enhancements.
Cosmetic modifications include:
- Body kits
- Custom paintwork or wraps
- Alloy wheels
- Interior LED lighting
- Window tints
- Exterior styling accessories
Performance modifications include:
- Suspension upgrades
- Performance exhaust systems
- Engine tuning or remapping
- Air intake and filtration upgrades
- Brake upgrades
- Steering improvements
While many modifications improve appearance or driving enjoyment, some may affect insurance premiums or even make the vehicle illegal for use on UK roads if they don’t comply with DVSA regulations.
How do modifications affect a car’s value?
There isn’t a simple answer, as the value of a modified car depends on the quality of the work, the type of modifications and the buyer.
In many cases, modifications can reduce resale value because most buyers prefer vehicles in original factory condition. Modified cars may also appeal to a much smaller audience, making them harder to sell.
However, professionally installed, high-quality modifications can sometimes increase value—particularly if they’re desirable within enthusiast communities. Examples include:
- Premium suspension upgrades
- High-quality alloy wheels
- Performance brake kits
- Professional engine tuning
- Upgraded security systems
If you’re unsure what your modified car is worth, getting an independent valuation is always worthwhile before advertising it for sale.
In terms of value, we looked into what can affect your car’s value, so you don’t have to and you can see exactly what can and cannot help your vehicle’s value.
What should you consider before selling a modified car?
Selling a modified car requires a little more preparation than selling a standard vehicle.
Before advertising your car:
- Fix any outstanding mechanical issues.
- Give the vehicle a thorough clean inside and out.
- Gather receipts for all modifications.
- Keep servicing and MOT records together.
- Be honest about every modification you’ve made.
Many buyers will want reassurance that modifications were carried out professionally and haven’t affected the vehicle’s reliability.
If you’re interested in car modifications, we looked into car modifications that sell to see how you could maximise the value of a modified vehicle.
Which car modifications are illegal?
Not every modification is road legal in the UK.
Examples of illegal or potentially illegal modifications include:
- Excessively loud exhaust systems
- Window tints that reduce visibility below legal limits
- Headlights or brake lights that don’t meet regulations
- Blue or flashing exterior lights
- Poorly fitted spoilers that obstruct visibility
- Engine modifications that fail emissions standards
Illegal modifications can lead to:
- MOT failures
- Fixed penalty notices
- Fines
- Insurance becoming invalid
- Vehicle prohibition notices
Always check UK regulations before carrying out any modification.
Will removing modifications increase my car’s value?
Sometimes.
Returning a car closer to its factory specification can make it more appealing to a wider range of buyers, particularly if modifications are very personal or extreme.
Removing modifications may be worthwhile if:
- The original parts are still available.
- The modifications are unpopular.
- The work can be reversed without damaging the vehicle.
However, removing expensive performance upgrades isn’t always financially worthwhile, especially if the cost of reversing them exceeds any increase in resale value.
Where’s the best place to sell a modified car?
You have several options.
Sell privately
Websites such as Auto Trader or eBay Motors allow you to advertise directly to enthusiasts who may appreciate the modifications. However, selling privately often means dealing with enquiries, negotiations and arranging viewings.
Specialist dealers
Some dealers specialise in performance or modified vehicles and understand their value. While this can be convenient, trade offers are often lower than private sale prices.
Sell through Jamjar
If you want a quicker and simpler option, Jamjar compares offers from a trusted network of UK buyers, helping you find a competitive price without negotiating yourself.
Should you declare modifications to your insurer?
Yes.
Even small cosmetic upgrades should usually be declared to your insurance provider. Failing to disclose modifications could invalidate your policy, meaning future claims might be refused.
Common modifications insurers often ask about include:
- Alloy wheels
- Suspension changes
- Performance exhausts
- Engine remaps
- Window tints
- Body kits
- Audio upgrades
If you’re unsure whether something counts as a modification, it’s always safer to tell your insurer.
Are modified cars more expensive to insure?
Usually, yes.
Insurance companies assess modified cars as a higher risk because modifications may:
- Increase vehicle performance.
- Make repairs more expensive.
- Increase theft risk.
- Change the way the vehicle handles.
The extent of any premium increase depends on the type of modification and your insurer, so it’s worth comparing quotes before carrying out any work.
Final thoughts
Modifying your car can make it more enjoyable to own, but it’s important to understand how changes affect legality, insurance and resale value.
If you’re planning to sell a modified vehicle, presenting it well, keeping documentation and being transparent about the work carried out can all help attract the right buyer and achieve the best possible price.
Value your modified car with Jamjar
Jamjar.com makes selling your car quick, easy and hassle-free. By comparing offers from a trusted network of UK car buyers, you get the best price without the stress of negotiating or haggling.
There are no hidden fees, no obligation to sell, and the entire process is 100% online. Whether your car is standard or modified, Jamjar helps you value it quickly and for a fair price, saving you both time and effort.