Companies allowing staff to watch World Cup matches on broadband at work could end up with a £1,000 fine if they do not have a TV licence.
A TV licence is required for any device that is "installed or used" for receiving television broadcasts.
With more than five million UK workers believed to have high-speed internet access at their desks, the BBC could make a killing if firms are unaware of the licence regulations.
"It does not matter how you are watching," said a TV licensing spokesman. " If you are watching a live match you will need a licence."
The Federation of Small Businesses urged its members and other companies to act on the advance warning and ensure that they are correctly licensed.
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