The 54-year-old Mourinho, who coached Madrid from 2010-13, now coaches Manchester United.
In the season just ended, he won three trophies in his debut campaign at Manchester United, although he drew criticism after a poor league performance in which United finished sixth in the Premier League.
The cases are about the profits made from image rights, not salaries from their clubs.
"All these companies' structures were used by the accused with the object of making physically opaque his image rights earnings", the state prosecutor's report read.
The accusations against Ronaldo have caused speculation in Portugal and Spain that he is considering leaving the country to play elsewhere.
Now with Paris Saint-Germain, Di Maria was found guilty of defrauding the Spanish government a sum of £1.14m during his time at Real Madrid between 2010 and 2014.
Manchester United manager Jose Mourinho has released a statement in which he has unequivocally denied the tax fraud allegations thrown his way on Tuesday morning. A Madrid judge will decide if the matter goes to court.
Barcelona's Lionel Messi was convicted of tax fraud previous year and given a 21-month prison sentence, although under Spanish law he did not have to spend time behind bars. The two were given 21-month jail sentences but neither is expected to serve prison time since it was a first offense and the sentence was under two years.
Barcelona defender Javier Mascherano also agreed a one-year suspended sentence with authorities for tax fraud last year.