Wayfair is among three firms which have been fined £6m in total by the competition watchdog over misleading sales tactics – with some customers set to receive refunds.
The Competition Markets Authority (CMA) has fined the online furniture retailer £4.8m and electronics retailer Appliances Direct £1.2m for misleading customers with time-limited offers.
Meanwhile, Gold's Gym has been fined £48,000 for not telling customers the total price of memberships.
Appliances Direct and Gold's Gym have been ordered to refund customers a total of £440,000. The BBC has contacted the three companies for comment.
Thousands of Appliances Direct customers will receive refunds of £25 each on average while 726 Gold's Gym customers will get refunds of up to £50, the BBC understands.
Hayley Fletcher, senior director for consumer protection at the CMA, said: "At a time when many households are carefully managing their budgets, people shouldn't lose out because of misleading sales tactics.
"Businesses must treat their customers fairly and make sure they comply with the law - or risk hefty fines."