The 54-year-old Mourinho, who coached Real Madrid from 2010 to 2013, was accused of "two offences against the public treasury", the prosecutor's office said in a statement.
Spanish media are reporting he will testify at the end of July but Sky sources understand Ronaldo has not received any official communication from Spanish tax authorities over his testimony on 31 July.
The prosecutor said Ronaldo used shell company in the Virgin Islands to cheat on his taxes.
In addition, they say he only declared 11.5 million euros of Spanish-related income from 2011 to 2014, while what he really earned during that time was close to 43 million euros.
It has been reported that these five players would be pleased if superstar Cristiano Ronaldo left Real Madrid this off-season.
The report claimed that Ronaldo leaving Real could benefit a few of these players, but none more so than Bale, who is believed to want a greater role under Zinedine Zidane.
The football world in Spain has been rocked by charges of tax evasion or corruption pressed against some of its top stars.
In 2016, soccer giant Messi, along with his father, was convicted of three counts of tax fraud equaling some $4.6 million earned from the use of Messi's personal brand.