Ticket reseller StubHub has been fined £900,000 for not showing fans the total price upfront when buying tickets.
More than 50,000 customers are expected to receive a refund with the average payout set to be around £10 per transaction, following an investigation by the Competition and Markets Authority (CMA).
"Hitting customers with hidden fees is illegal. It's not fair to draw people in with what looks like a good deal, only for them to find the real price is higher when they get to the checkout due to extra charges that can't be avoided," said Emma Cochrane, executive director of consumer protection at the CMA.
The regulator said StubHub would contact fans about their refund.