The most ardent football fans in Britain could be inadvertently raising the cost of their any driver van insurance by fixing stickers of their team's crest on their vehicle.

This follows a piece of research by Auto Express that was carried out in conjunction with the British Insurance Brokers' Association (BIBA) and a motor insurance company.

The study found that stickers could count as a modification as, under many insurer’s rules, a modification is deemed to be any change that is made to a van once it has been sold by its manufacturer.

As such, failing to declare a football sticker, satnav system or any other addition to the body or interior of a van could potentially invalidate a van insurance policy. In the case of a football sticker, some insurance companies may contend that it makes the vehicle vulnerable to vandalism attacks by fans of rival football teams. Furthermore, once declared, such modifications can add to the cost of a premium by as much as £100.

However, not all football-crest-related items are considered modifications. For example, a football club air freshener – a very popular product in the UK right now – is fine so long as there is only one and it does not interfere with the driver’s view.

If in doubt, notify your insurer

If you are in doubt as to whether something counts as a modification, it is always best to check in with your insurer so that they confirm its status. This is true even in cases where a modification is for the purposes of improving safety. For example, sometimes insurance companies used to increase the cost of a premium when drivers fitted winter tyres to their vans. However, in 2011, 70 percent of insurance companies became signatory to an agreement to not increase premium prices for drivers who fitted winter tyres to their vehicles – but most still wish to be informed.

The same is true of modifications such as tow bars and roof racks; it is unlikely they will increase the cost of your premium, but your insurer is likely to want to be informed regardless.

Furthermore, it is important to inform your insurer of any of the following modifications:

• Tinted windows
• Spoilers, skirts and valances
• Extra lights
• Upgraded upholstery
• Upgraded brakes
• Stripes, decals and badges
• Replacement seats
• Turbo/supercharging engine
• Exhaust system changes
• Flared wings, bonnet bulges
• Specialised paintwork
• Roof rack
• Tow bar
• Hand controls
• Alloy wheels
• Sat nav
• Parking sensors

The theme here is clear: if in doubt about whether something constitutes a modification, let your insurer know.