The Real Madrid and Portugal star was accused by Spanish prosecutors in June last year of defrauding tax authorities of £12.9million (€14.8million), Daily Star reported.
He initially denied allegations that from 2011 to 2014 he defrauded the Spanish treasury when he appeared in court last year.
But the former Manchester United ace has now reportedly pleaded guilty to four charges of fraud in exchange for a lesser penalty.
He accepted a two-year suspended prison sentence and a fine worth £16.5million (€18.8million), according to Spanish newspaper El Mundo.
Ronaldo, 33, will not face any time behind bars because he has no previous convictions.