Baby on board, football clubs and even advertisements - these are just some of the stickers drivers like to add to their car's rear window.
But showing your colours on your motor could actually land you with a hefty £300 fine - and even six points on your licence.
That's because stickers can count as "modifications" in the eyes of insurance companies and could end up invalidating your cover.
The definition of a car modification is very strict, according to Auto Express and the British Insurance Brokers Association.
“While some additions to your car are obvious candidates for telling your insurer about, many motorists will be surprised by the strict definition of modification, and how even a sticker in the back window could void your policy,” said Auto Express consumer editor Hugo Griffiths.
In 2015, Reverend Wena Parry, who was 75 at the time, sent photos of her car as part of a claim, only for the insurance company to say she had 10 days to explain why she hadn't told them about the stickers she applied and warned "the policy may be declared void".
In a letter Age UK Insurance said: "These modifications do not fit our acceptance criteria for motor insurance. Cover would have been declined if we had been made aware of these at the time of purchasing your policy."
While her insurer did, eventually, pay out - the warning is there for all to see.
“Failing to declare something as humble as paint protection film or different alloy wheels could void a policy entirely, potentially costing thousands in the event of an incident, and even putting motorists at risk of a £300 fine and six penalty points,” Griffiths added.
Next time you want to show support for your team, best steer away from your car!
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