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Written by
Julie Daniels
Motor insurance comparison expert
20 NOVEMBER 2023
6 min read
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Car Modification – How to Avoid Fines

From installing a subwoofer to switching out the engine, there are lots of ways drivers can alter their cars to improve either, the performance or the look of their vehicle.

Any car that has been changed in some way since it was manufactured is considered to be a modified vehicle and while not all changes are illegal, there are certain rules that need to be followed to ensure the alterations aren’t breaking the law.

To help drivers avoid hefty fines and penalties, we’ve taken a look at some of the different regulations regarding common car modifications. Our experts also shed light on how making changes to your car can impact your insurance.

Common car modification fines

1. Lowering suspension

Fine: £2,500
Penalty Points: 3

Lowered cars aren’t necessarily breaking the law, but the alteration must not interfere with the steering or affect the height of the headlights on the car. Suspension changes should always be carried out by a competent mechanic and components should never be cut and welded together as this can make the car dangerous to drive. Altering the height of the car could also lead to issues getting over speed bumps, which can result in serious damage to the vehicle.

If drivers are deemed to be using their car in a dangerous condition because of changes to their suspension, they could be hit with a fine of £2,500, plus three penalty points on their licence.

2. Adding large spoilers

Fine: £2,500
Penalty Points: 3

Adding a spoiler to a vehicle isn’t illegal, but the spoiler must be securely fitted to the bodywork and shouldn’t have any dangerously sharp edges. Under regulation 30 of the Highway Code, the spoiler also shouldn’t obstruct the driver’s view of the road or traffic.

As with lowering the suspension, if a spoiler is affecting a motorist’s control of a vehicle to such an extent that they are deemed to be using it in a dangerous condition, then they could face a fine of £2,500, and three penalty points.

3. Tinted headlights

Fine: £2,500
Penalty Points: 3

Headlights can be tinted, but by no more than 50%. The tint should also not alter the colour of the light, meaning they should remain white or yellow at the front, and red at the rear.

The Highway Code states that car lights must be working at all times, and they should also be kept clean and clear. If this isn’t the case, then again drivers would be seen to be using their vehicle in a dangerous condition, and would face the consequence of a £2,500 fine, and three penalty points.

4. Installing a subwoofer

Penalty: Vehicle could be seized by the police

Installing a subwoofer isn’t against the law, but if you’re deemed to be playing it loud enough to cause alarm, distress, or annoyance, then the police have grounds to stop the vehicle.

Under the Police Reform Act 2002, they also have the power to seize and remove the car if a driver fails to adhere to a warning about noise levels.

5. Tinting windows

Fine: £60 and car taken off road until window tint is removed 
Penalty Points: 3

The law states that the front windscreen of a car must let at least 75% of light through, while the front side windows must let at least 70% in.

It is illegal to fit or sell glass that breaks these regulations. If your windows are tinted too heavily, you could be given a ‘prohibition notice’ which will stop you from using your vehicle until the extra tint is removed. Alternatively, you might receive a penalty charge notice, which would result in a fine of £60 and three penalty points.

6. Altering number plates

Fine: £1,000

There are several things to consider when altering your number plates. To be legal, a plate must have the correct font, colour, and character spacing, and also be made of certain materials.

With private number plates, you must have the correct documentation to prove you have the right to use it such as a V750 certificate or V778 retention document.

You can also ‘retain’ your private plate even if it’s not currently on a vehicle, but you must put it on retention through the DVLA website, or risk losing the plate. You also need to renew your right to use a personal plate every 10 years if it’s not being used on a vehicle.

Failure to comply with any of these regulations could result in a fine of £1,000.

7. Changing the colour of a car or swapping the engine

Fine: up to £1,000

Altering the colour of your car, either by wrapping or respraying, is perfectly legal, but you must update your V5C registration certificate if you do so. You must also update your VC5 if you switch your engine for a different one. 

Failure to notify the DVLA of these changes to your vehicle will result in a fine of up to £1,000.

8. Modifying the exhaust to make it louder

Fine: £50 and car taken off road until exhaust is removed 

There are specific rules around how much noise vehicles can make on public roads. It’s therefore illegal to modify your exhaust to make a vehicle louder after it has been ‘type approved’ — meaning it meets environmental and safety standards.

The police can take action if your vehicle’s silencer doesn’t work in the way it was designed, or if you’re deemed to be driving in a way that creates too much noise.

If you are caught with an excessively loud exhaust, you could face an on-the-spot fine of £50, and your car may be taken off the road until the offending exhaust is removed.

Author image Julie Daniels

What our expert says...

How can car modifications affect insurance?

“No matter how minor the modifications are, any alterations to a car can potentially impact the cost of your car insurance. Often it will cost more to insure a modified car because of factors such as: a greater possibility of theft, higher risk of speed-related accidents, or simply because your car has increased in value and may now cost more to repair. 

If you decide to modify your car while you have an existing insurance policy, you need to notify your provider about the change. Ideally, you should check with your provider before altering your vehicle, to find out how it might affect your premium, or if there will be any amendment fees involved.

You must also do your research to ensure that all your modifications are legal. If any changes break the law, then you won’t be able to take out cover at all, and you’ll also risk hefty fines and penalties.”

- Julie Daniels, Motor insurance comparison expert

Methodology and Sources

The study reviewed the Highway Code to outline the rules, fines, and penalties.