The 33-year-old was accused last year of evading €14.7million in taxes relating to his image rights between 2011 and 2014.
According to reports in Spain on Monday, Ronaldo's legal team made a settlement offer of €3.8m, plus admission of wrongdoing, which was rejected by the country's tax authorities.
The Portugal international appeared in court last year to respond to the allegations, insisting "I always pay what I have to pay; I do things the right way and I will continue to do so". His representatives, Gestifute, have also persistently denied any wrongdoing.
The Real Madrid star took to Instagram on Monday to hit back at those who would try to "spoil" his spectacular return to form in 2018.
"Don't try to spoil the beautiful moment I'm living through with fake news," he wrote in Portuguese, before adding in English: "Life is good. Blessed".
Ronaldo scored four in Madrid's 6-3 LaLiga win over Girona on Sunday, taking his tally to 21 goals in just 13 games since the turn of the year.
Photo Getty Images. Caption: Real Madrid forward Cristiano Ronaldo