In a statement released on Tuesday, a prosecutor in Madrid said the 54-year-old had committed two counts of tax fraud in 2011 and 2012, saying that "corporate structures were used by the accused in order to hide revenues generated from his image rights".
Tax fraud investigations in Spain have been ongoing for some time with a number of high profile individuals taken to court over charges in relation to the crime.
Real Madrid president Florentino Pérez obviously doesn't want him to leave and he told Spanish radio station Onda Cero (via The Sun) that they still haven't received any offers for Ronaldo, Morata and James Rodríguez.
Portugal's Cristiano Ronaldo calls for referee's attention during the Confederations Cup, Group A soccer match between Portugal and Mexico, at the Kazan Arena, Russia, Sunday, June 18, 2017.
Ronaldo's trouble coincided with the same Madrid-based prosecutor's office accusing Mourinho of two counts of tax fraud.
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Mourinho coached Real Madrid from 2010 to 2013, guiding the club to wins in LaLiga, the Copa del Rey and the Supercopa de Espana. A claim for the money has been presented at a local court, reports the Daily Mail.
The company has published a tax-related document in Mourinho, which dates back to July 3, 2015.
Falcao himself is suspected of failing to correctly declare € 5.6 million of income earned from image rights between 2012 and 2013 while he was at Atletico.
Messi and his father were given 21-month sentences for three counts of tax fraud but did not go to prison, while Mascherano was given a one-year sentence for tax evasion.
Barcelona's Lionel Messi was convicted of tax fraud previous year and given a 21-month prison sentence, although under Spanish law he did not have to spend time behind bars.