Lionel Messi and his father have been accused of defrauding Spanish tax authorities of more than €4m (£3.4m).
The World Player of the Year and his father Jorge allegedly filed fraudulent tax returns for the years 2006, 2007, 2008 and 2009, according to a spokesman for the prosecutor's office for tax crimes in Catalonia.
The 25-year-old, who is currently on international duty, has denied the allegations.
Messi and his father are suspected of using companies abroad - in Belize and Uruguay - to sell the player's image rights. The accusation is that by using companies based outside Spain, Messi and his father have avoided paying more than €4m in tax.
Writing on his Facebook page, Messi wrote: "We have never committed any infringement. We have always fulfilled all our tax obligations, following the advices of our tax consultants who will take care of clarifying this situation."
The Argentina international is among the wealthiest footballers in the world. He is understood to command a salary in excess of €16 million (£13.5m) from his club while endorsements from sponsors Adidas, PepsiCo and P&G are in excess of that figure. In the most recent Forbes' rich list he came 10th among the top-earning athletes.
If convicted, Messi could face up to six years in jail and a large fine, according to Spain's EFE news agency.