Cristiano Ronaldo faces a brutal return to Madrid before starting pre-season training with Real Madrid as he is expected in court on Monday, accused of evading millions in taxes.

The 32-year-old — the world's highest paid athlete according to Forbes magazine — will be questioned by a court in Pozuelo de Alarcon, a wealthy suburb of Madrid where he lives, over allegations he evaded €14.7 million ($17.2 million) in tax.

The Portuguese star follows in the steps of his arch-rival, Barcelona forward and Argentina star Lionel Messi, who was found guilty of the same offence in 2016, although the sums involved were smaller.

Madrid's public prosecutors accuse Ronaldo of having taken "advantage of a company structure created in 2010 to hide income generated in Spain from his image rights from tax authorities".

They say this was a "voluntary and conscious breach of his fiscal obligations in Spain". Prosecutors accuse the four-time world player of the year of evading tax via a shell company based in the British Virgin Islands and another in Ireland, known for low corporate tax rates.

In addition, they say the Real Madrid striker only declared €11.5 million of Spanish-related income from 2011 to 2014, while what he really earned during that time was close to €43 million.

And finally, they accuse him of "voluntarily" refusing to include €28.4 million in income linked to the sale of his image rights for the 2015 to 2020 period to a Spanish company.

Ronaldo has defended himself, saying his "conscience is clear".

But the allegations still took their toll, and the man with the "CR7" brand, Real's all-time top goalscorer, threatened to leave Spain over the affair, giving supporters a fright. He has since hinted he will stay on, telling Spanish sports daily Marca that he would like to continue to win trophies for Real.

Ronaldo is not the only footballer to fall foul of authorities in Spain, which is only just recovering from a damaging economic crisis that saw countless people lose their jobs and inequalities rise.

Messi was sentenced to a 21-month jail sentence and €2.09 million fine in 2016 for tax fraud.

His prison sentence has since been replaced by another fine of €252,000, which corresponds to €400 for each day of jail.

Barcelona's Argentine defender Javier Mascherano, meanwhile, agreed a one-year suspended sentence with authorities for tax fraud last year.

Brazil star Neymar, another Barcelona forward, and his parents are also due to stand trial for alleged corruption over his transfer from Santos in 2013.

Real have not been spared either. Apart from Ronaldo, former player Angel di Maria, Portuguese defender Fabio Coentrao and Jose Mourinho, who coached the club from 2009 to 2013, have all been accused of tax fraud.

All are clients of super-agent Jorge Mendes, who was also questioned and put under official investigation last month by a Spanish court investigating alleged tax evasion by Monaco striker Radamel Falcao, another footballer in his stable.

Mendes defended himself, telling the closed door hearing that he "never" advised players in tax matters. Where Ronaldo is concerned, Mendes's company Gestifute has denied any "fiscal set-up" and said "the player didn't hide anything".

But if he were put on trial and found guilty, Ronaldo risks "a fine of at least €28 million" and could potentially be jailed for three-and-a-half years, the Gestha union of experts at Spain's Inland Revenue has said.

Since extending his contract last November until 2021, Ronaldo is the highest paid sports star in the world with $93 million (€80 million) earned in 2016-2017, according to Forbes.