He's coaching Manchester United.
The allegations have led to uncertainty about the 32-year-old's future at the Santiago Bernabeu, with Manchester United linked as a possible destination should he opt to leave Spain.
In a statement, Ronaldo's management company Gestifute said there had been no attempt to evade taxes. "To this date, neither the Spanish tax authorities, nor the public prosecutor have contacted Jose Mourinho or his advisers who were hired for the inspection process".
The accusations come just a week after Spanish prosecutors brought a parallel case against Mr Ronaldo, Real Madrid's star striker who allegedly withheld taxes worth €14.8 million.
Revelations from the whistleblowing website Football Leaks have lifted the veil on the practices supposedly used by Mendes to optimise often enormous earnings from image rights by his clients. "I'm sure he will speak to us about what has happened [with the tax case], which has obviously affected his credibility, and we'll see what happens".
Prosecutors said he had failed to declare revenues from his image rights in his Spanish income tax declarations from 2011 and 2012, "with the aim of obtaining illicit profits". The main claim is in connection with allegedly undeclared income from the sale of image rights by using companies based outside the country.
In three years with Real Madrid, Mourinho won La Liga in 2012 and the Spanish Cup in 2011.
Mourinho was manager of Real Madrid from 2010 to 2013 before he returned to the Premier League for his second spell in charge of Chelsea. This is similar to deals struck with the Spanish taxman by fellow Argentinians Javier Mascherano and Lionel Messi a year ago.
He is due to play for Real Madrid against Barcelona in a friendly in Miami on July 29.