The Juventus forward, who was facing charges stemming from his days at Real Madrid, was in court for about 45 minutes and signed an agreement which will cost him nearly 19 million euro ($A30.3 million) in fines.

Ronaldo arrived at court in a black van and was wearing a black sports coat and black trousers.

He walked up some stairs leading to the court house and even stopped to sign an autograph.

Ronaldo made the deal to plead guilty with Spain's state prosecutor and tax authorities last year.

In Spain, a judge can suspend sentences for two years or less for first-time offenders.

In 2017, a state prosecutor accused Ronaldo of four counts of tax fraud from 2011-14 worth 14.7 million euro ($A23.4 million).

The Portuguese superstar was accused of having used shell companies outside Spain to hide income made from image rights.

Australian Associated Press