Dutch club Utrecht are taking Swansea City to the Court of Arbitration for Sport (CAS) over the transfer of Michel Vorm from the Swans to Tottenham in 2014.
Utrecht say they are owed a 30% sell-on fee for the goalkeeper, which they claim was written into the deal when Swansea signed him for £1.5m in 2011.
The Welsh club insist Vorm's 2014 transfer to Spurs - which was made in conjunction with that of Ben Davies as Gylfi Sigurdsson moved the other way - was a free transfer, but a hearing will be held at CAS on January 29 next year.
Utrecht have questioned why Vorm, a Holland international with two years on his contract at the time, was given a zero value in the transactions and FIFA confirmed last summer they were investigating the transfer following a formal complaint by the Eridivisie outfit.
Vorm signed a four-year contract at Tottenham and Swansea insisted last summer that the transfer did not break any rules.
"The transfer of Michel Vorm was conducted and concluded correctly under Premier League rules," a Swansea spokesman said.
"It was approved by the Premier League and also FIFA via their TMS (Transfer Matching System).
"While we have been in contact with Utrecht as a matter of courtesy, we will continue to conduct our business in the best interest of our football club and our supporters, and not based on the views of other clubs.
"Unlike some countries abroad, we do not have third party ownership of players in Britain. The club will not be commenting further on this matter."