A, based in the Virgin Islands, before September 2004 and that he knowingly used a "business structure" involving several companies to hide his income from his image rights.
Jose Mourinho is facing allegations of tax fraud in Spain worth almost £3 million.
"From now on it will be the judge in charge of the case who will take the necessary steps to determine the possible responsibilities of Mr Mourinho".
The Manchester United boss released a statement tonight to state that "neither the Spanish tax authorities nor the public prosecutor have contacted him or his advisers".
A prosecutor said Mourinho, 54, did not declare income from image rights in order to get an "illicit benefit".
Former Manchester United winger Angel Di Maria has been sentenced to a year in prison after admitting to tax fraud.
Ferdinand knows Ronaldo well, having played with him under Sir Alex Ferguson at Manchester United before his eventual transfer to Real Madrid in the summer of 2009.
Jose Mourinho, meanwhile, has come out fighting in a row with the Spanish tax authorities, claiming he paid more than €26million (£23m) between 2010-2013.
Ronaldo and Mourinho are the latest members of the soccer elite to be accused of tax fraud in Spain.
The accusation against Mourinho comes a week after the Madrid-based prosecutor's office accused Real Madrid forward Cristiano Ronaldo of defrauding Spain's tax office of 14.7 million euros ($16.5 million).
Other clients of Mendes who have ended up in Spain include the Portuguese full-back Fabio Coentrao - on the verge of joining Sporting Lisbon on loan from Real Madrid - and Colombian striker Radamel Falcao, now with Monaco but formerly at Atletico Madrid.
The Real star has been summoned to testify on July 31. Ronaldo has denied the charges.
Under Spanish law, a first-time offender is not required to serve time in jail for a sentence below two years.
Neymar, his father, and Javier Mascherano have also had their troubles with tax over the last couple of years.
Also past year, Barcelona star Lionel Messi and father Jorge Horacio Messi were found guilty of tax fraud and given 21-month sentences, which will likely be suspended.