Condé Nast Publications has won a test case versus the Inland Revenue which could reap millions of pounds for media companies.
In June last year the High Court dismissed moves by Condé Nast to claw back more than 20 years' worth of overpaid VAT.
Today though three appeal judges over-turned that decision and ruled in favour of the publishing house which is behind titles such as Vogue, GQ, Tatler and Vanity Fair.
Condé Nast had argued that it was entitled to recover the extra input VAT in respect of staff entertainment it paid from 1 April 1973 to 30 April 1997. It had failed to deduct those figures when accounting for VAT in past periods and the High Court had ruled that it had left it too late to seek repayment.
The judge had ruled that, under complex European law, Condé Nast's claim had to be made within a "reasonable period" from 5 August 2002.
Today though the Appeal Judges ruled that he was wrong. Now their decision is said to pave the way for many other companies to seek repayments which top accountants, Deloittes, say would run to over £100 million collectively.
Tony McClenaghan, head of Indirect Tax at Deloitte said: "This case potentially affects all businesses that might have valid claims for under recovered input VAT. Any company which may benefit from this case should consider submitting a claim to HM Revenue & Customs straightaway.
"Subject to petitioning the House of Lords for an appeal, the Government will now be forced to remedy the defective law.
"We estimate that taxpayers who have already lodged claims will seek immediate repayment of the overpaid VAT. The claims are likely to amount to at least £100 million."