The Spanish media have claimed the Real Madrid star must be in the courtroom in Pozuelo at 11am local time for the beginning of the case.
Those allegations were denied in a statement by Ronaldo's management company Gestifute, while Real Madrid say they have "full confidence" in a player who "will prove his total innocence in this process".
The Spanish prosecutor says the Real Madrid forward knowingly used a business structure to hide his image rights income in Spain between 2011 and 2014.
Real Madrid president Florentino Perez has played down talks that Cristiano Ronaldo is leaving the Santiago Bernabeu club anytime soon, saying that no team has so far made a bid for their star striker.
Another player linked with a move away from Madrid is James Rodriguez after a frustrating stop-start campaign.
The 24-year-old Morata, who was married in Venice over the weekend, is believed to be rated at £79milllion by Real, but Cristiano Ronaldo's situation is believed to have complicated matters.
Real Madrid president Florentino Perez has spoken for the first time about the future of Cristiano Ronaldo amid rumours he wants out of the Spanish capital following accusations of tax fraud.
"I've not spoken with Nasser (Al-Khelaifi, PSG president) or with anybody", Perez said. "All this is very unusual", Perez said.
But Perez said hasn't received offers for either player.
The main contender for the 32-year-old striker considered his former club "Manchester United" capable of pay for the Portuguese record in the history of football of 200 million euros. A return to Manchester United would keep him in his No. 6 spot, but any other realistic destination would drop him lower in the ranks.
In European competition, he has led Porto to UEFA Cup victory in 2003 and a Champions League triumph in 2004, and also won the Champions League with Inter Milan in 2010.