The former Real Madrid team-mates are dealing with accusations first levied against them within the space of a year. Ronaldo was accused in 2017 and subsequently opted to pay a fine worth £16.4 million (€18.8 million).
Meanwhile, Alonso will attend the Madrid Provincial Court to respond to an accusation brought against him back in March 2018. The ex-Real Sociedad, Liverpool and Bayern Munich midfielder is said to have failed to declare image rights, leaving him owing as much as £1.7 million to authorities in Spain.
Ronaldo was handed a suspended jail term last year after the Spanish government had previously declined his offer to settle things by paying £12 million, per El Mundo (h/t BBC Sport).
The 33-year-old, who moved from the Spanish capital to Juventus for £99.2 million back in the summer, eventually agreed to the fine imposed on him. He is "expected to plead guilty" when he appears in court, hoping to bring an end to the matter.
His two-year prison sentence would be served on probation under Spanish law.
Ronaldo is set to play for Juve just 24 hours before his scheduled court appearance when the Serie A leaders host Chievo at the Allianz Stadium on Monday. The prolific forward was pictured in training ahead of the match, per MailOnline's James Ayles.
Meanwhile, Alonso denied the accusations when they were first brought. The 37-year-old could face up to five years behind bars if prosecutors prove him guilty.
Alonso's case could also end with the FIFA World Cup winner being hit with a fine worth £3.5 million, per the Daily Mirror's Alex Richards.
He noted how Alonso is facing three counts of tax fraud involving the sale of image rights through accountant Ivan Zaldua Azcuenaga to Ignasi Maestre Casanova and Kardazli Commercial Services, which is accused of being a shell corporation facilitating the return of the proceeds directly to Alonso.