According to El Confidencial, Ronaldo will appear before a Spanish judge in Pozuelo next month to give evidence, which means that he is likely to miss Real's pre-season friendly against Barcelona in Miami on July 29.
"We haven't spoken to De Gea", Perez told the Spanish radio station Onda Cero.
Ronaldo has been linked with a return to Manchester United but a move could cost the Premier League side anything up to the Portugal international's €1bn release clause.
Ronaldo has been accused by prosecutors of defrauding Spanish tax authorities out of €14.7million, a claim he has strenuously denied.
The 32-year-old is now away with Portugal at the Confederations Cup in Russian Federation, where he has so far evaded questions over his future - including skipping the traditional man-of-the-match press conference after Sunday's draw with Mexico.
Meanwhile, Florentino Perez admitted he has not spoken with the Portuguese about his desire to leave the club in the wake of the investigations. "We don't want to disturb his concentration with the national team", said Perez.
"Everyone says he's a great player, he's going to be the substitute for Buffon", Perez said.
Perez, a 70-year-old construction magnate, was elected unopposed Monday for a third term in charge of Europe's most successful club.
And among the first issues he will have to deal with is Ronaldo, who he bought in 2009 from Manchester United for a record €94m.
"We're used to being the subject of intense transfer speculation during transfer windows", Rummenigge said in a statement.
"As a rule, we do not comment on these rumours".
The four-time World Footballer of the Year has helped Real win the Champions League three times and La Liga twice.