Machines in Mecca bingo halls formed part of the claim
Rank Group - which runs casinos and Mecca bingo halls - has won a High Court case which its advisers say could cost the taxman up to £500m.
The court said Rank was entitled to £62m from value added tax overpaid on slot machines and bingo takings.
This follows some UK gaming and bingo machines being exempt from VAT while similar machines were subject to the tax - a disparity illegal under EU law.
The judge said that there were over 1,000 similar claims outstanding.
Accountancy firm Deloitte estimated that £500m could be returned, with pub chains, bookmakers and amusement arcade operators among those having made similar claims to get VAT repaid.
Those running fruit machines at motorway service stations and holiday camps could also be in line for refunds, said Barney Horn, indirect tax partner at Deloitte.
Rank said it "welcomed" the court ruling.
Meanwhile, HM Revenue and Customs (HMRC) said it would consider the case before deciding whether or not to appeal.
It added it would soon issue guidance for those who felt they may be entitled to reclaim overpaid VAT.
Principles set out by the European Court of Justice "require the same or similar services to be treated in the same way for the purposes of VAT" Mr Horn said.
There was a disparity in tax rules until until December 2005, when HMRC amended the law to tax all of these gaming machines.
One of the claims relates to interval bingo - an mechanised game played during gaps between rounds of traditional bingo.
The other claim relates to gaming machines, or slot machines. in Mecca Bingo clubs and Rank's Grosvenor casinos.