The prosecutor said Ronaldo used a shell company in the Virgin Islands to hide the true amount of income made from image rights, among other means of illegally reducing the amount of taxes he paid.
Ronaldo's representatives have denied the allegations and insisted that their client's taxes are in order, while Real Madrid have also thrown their support behind the superstar forward and backed him to prove his innocence.
Spanish prosecutors filed a lawsuit against Cristiano Ronaldo for alleged tax fraud of £13m (€14.7m) between 2011 and 2014.
Cristiano Ronaldo reacted to accusations that he evaded paying taxes of 14.7 million euros ($16.4 million) by saying that remaining silent was the "best answer".
"The accused took advantage of a company structure created in 2010 to hide income generated in Spain from his image rights from tax authorities, which is a "voluntary" and "conscious" breach of his fiscal obligations in Spain," it said.
Gestifute, the agency representing the Portugal captain, said in a lengthy statement posted on its website the matter is a complex financial one.
Prosecutors accuse the Portugal worldwide of evading tax via a shell company based in the British Virgin Islands and another in Ireland, known for its low corporate tax rate.
Ronaldo is the latest high-profile soccer player to run afoul of Spain's tax man.
The prosecutor's office alleges that Ronaldo had defrauded the tax authorities of €1.4 million in 2011, €1.7 million in 2012, €3.2 million in 2013 and €8.5 million in 2014.
Tollin Associates then ceded his image rights to a company in Ireland called Multisports&Image Management Ltd which was responsible for managing them.
Mendes was summoned to appear before the court of instruction at Pozuelo de Alarcon, close to Madrid, on June 27. He is unlikely to go to prison as under Spanish law sentences under two years can be served under probation.