Gestifute, a firm representing Manchester United manager Jose Mourinho and former player Cristiano Ronaldo, has denied designing ways to help clients evade millions in taxes.
The allegations are reported by an international consortium of media organisations after a huge data leak of more than 18 million documents.
Real Madrid star Ronaldo is alleged by one of the publications, Dutch website NRC, to have moved €63.5 million to a tax haven in the Virgin Islands at the end of 2014.
It is claimed that Mourinho's complex financial affairs involved keeping money in a Swiss bank account owned by a British Virgin Islands-registered company.