Modifying a car is a great way to enhance its performance, personalise its look, or add practical features. However, not all modifications go unnoticed by insurers. Failing to declare changes could lead to policy cancellations, rejected claims, or higher premiums if caught later.
Many drivers assume minor modifications, such as alloy wheels or performance tweaks, don’t need to be reported. However, even small changes can alter how a car handles, its risk profile, or its value—factors that insurance companies take seriously.
For example, performance upgrades may increase speed and power, making accidents more severe. Suspension changes can alter a car’s stability, impacting handling in emergency situations. Even aesthetic changes like decals or body kits can make a car more attractive to thieves or lead to assumptions about driving behaviour.
One common misunderstanding is that factory upgrade options don’t count as a modification. If a car didn’t leave the factory with a particular feature, such as aftermarket alloy wheels or a sports exhaust, it needs to be disclosed.
Another misconception is that cosmetic modifications don’t matter. Do you have to declare stickers on your car? In short, yes, even something as small as stickers, going further to body kits, or custom paintwork can affect how a car is assessed for risk, especially if they make it more eye-catching.
Even modifications done for safety, such as upgraded brakes or roll cages, should be reported. While they may improve safety, insurers may still adjust premiums due to the impact on vehicle performance.
Failing to declare car modifications to your insurer can have serious consequences. If an insurer discovers undeclared changes after an accident or routine check, they may cancel your policy, refuse to pay out on claims, or even void your insurance entirely.
Undisclosed modifications can also lead to significantly higher premiums when insurers reassess the policy. Some providers may refuse cover altogether if they believe modifications increase risk beyond their acceptable limits.
In some cases, non-disclosure can have legal implications. Driving without valid insurance—even unintentionally—is illegal in the UK and could result in fines, penalty points, or vehicle seizure.
So being upfront ensures you have the right cover in place and prevents unexpected financial or legal issues.
In this article, we’ll break down five key car modifications that must be declared. Whether you’re upgrading performance, enhancing aesthetics, or branding a business vehicle, understanding what insurers require can save you from unexpected costs.
1. Alloy Wheels and Tyres
Upgrading to aftermarket alloy wheels or changing tyre specifications can impact a vehicle’s performance and safety, making them modifications insurers need to know about.
Lighter alloy wheels can improve handling and fuel efficiency, but they may also make a car more attractive to thieves. Low-profile tyres, while offering better grip, can increase the risk of damage from potholes or kerbs, leading to higher claim costs.
Insurers assess these changes based on size, material, and finish. If you fit larger wheels than the manufacturer’s original specifications, it can affect speedometer accuracy and suspension wear, both of which insurers consider risk factors.
When declaring wheel and tyre modifications, provide details on size changes, aftermarket brands, and any specialist coatings or finishes, as these can influence your policy terms and premiums.
2. Suspension Modifications
Adjusting a car’s suspension—whether lowering it for better handling or raising it for off-road use—directly impacts stability and safety, making it a key modification insurers consider.
Lowering suspension reduces body roll and improves aerodynamics, but it can also lead to a harsher ride and increased risk of damage from speed bumps or uneven roads. On the other hand, raising suspension for off-road driving can alter a vehicle’s centre of gravity, increasing the risk of rollovers.
Insurers assess these modifications due to their potential effect on handling and accident likelihood. Common changes include coilovers, lowering springs, air suspension kits, and lift kits.
When notifying your insurer, provide details on the type of modification, whether it was professionally installed, and if it affects the vehicle’s ground clearance or structural integrity.
3. Engine and Performance Upgrades
Modifying an engine for more power changes a car’s risk profile, making it one of the most scrutinised modifications by insurers. Even small upgrades can lead to higher premiums or restricted cover.
Performance modifications include ECU remaps, turbochargers, superchargers, and upgraded exhaust systems. These increase horsepower and torque, which insurers associate with higher speeds and potentially risky driving behaviour.
Some insurers may allow minor engine upgrades without major policy changes, while others may require specialist cover for heavily modified vehicles. It’s crucial to declare all changes, even if they seem insignificant.
4. Stickers and Decals
Many drivers don’t realise that stickers, decals, and wraps can be classified as modifications. While they don’t change a car’s performance, they can affect how insurers assess risk.
Branding decals and business wraps, for example, may indicate commercial use, requiring a different type of cover. Large reflective decals or full-body wraps can also impact visibility and draw attention from law enforcement, which insurers take into account.
To avoid policy issues, always declare noticeable stickers or wraps, especially if they cover a significant portion of the car.
5. Body Kits and Spoilers
Body kits and spoilers can improve aerodynamics, add a sporty look, or enhance stability at high speeds—but they also change how insurers assess a vehicle.
Beyond cost, certain modifications can impact safety. Poorly fitted body kits may weaken structural integrity, while oversized spoilers can affect rear visibility.
Since modifications like these often signal enthusiast-driven vehicles, some insurers may classify them as higher risk. Always inform your insurer of any changes to ensure your policy remains valid and to avoid unexpected premium increases.
Declaring vehicle modifications ensures you maintain valid cover and avoid policy disputes. Even minor changes can influence premiums or risk assessments, so full transparency is key.
If your insurer increases premiums significantly, specialist providers offer better rates for modified vehicles.
Being upfront keeps your policy intact, prevents costly surprises, and ensures your car is insured correctly.