Messi, 28, and his father, Jorge Horacio Messi, are accused of using a chain of fake companies in Belize and Uruguay to avoid paying taxes on 4.16 million euros ($4.7 million) of Messi’s income earned through the sale of his image rights from 2007-09.
They have been charged with three counts of tax fraud.
The Barcelona court hearing the case adjourned the trial at around noon local time (1000 GMT) after considering preliminary legal questions because of the absence of witnesses who had been due to appear, including Messi’s mother Celia Cuccitini.
The trial will resume on Wednesday at 10am (0800 GMT) with testimony from the witnesses and experts.
Messi had planned to be in Barcelona for the start of the trial but a lower back injury he suffered during a friendly against Honduras last week prevented him from doing so, defence lawyer Javier Sanchez-Vera said.
The Argentina captain was resting in his hometown of Rosario, located 300 kilometres (185 miles) north of Buenos Aires on Monday. Messi and his father are due to take the stand on Thursday on the last day of the trial.
Under Spanish law, a defendant is not obliged to attend the full trial if prosecutors seek a jail sentence of less than two years.
Spanish prosecutors are seeking a jail sentence of 22-and-a-half months for Messi and his father if they are found guilty, plus fines equivalent to the amount that was allegedly defrauded.
But any such sentence would likely be suspended as is common in Spain for first offences carrying a sentence of less than two years.
– ‘Dad handled the cash’ –
The Barcelona forward and his defence team have argued that the player’s father handled his finances without reporting to him, and that the striker was not aware of any wrongdoing.
“My dad handled the cash,” Messi said in September 2013 when he was questioned by a judge investigating the case at a court in Gavia, a town on the outskirts of Barcelona where the footballer lives.
He reportedly told the judge at that hearing that he never looks at the contracts he signs.
“I signed things, but I never look at the contracts. I don’t know what I sign,” Messi said according to the daily El Periodico, which got access to his September 2013 statement to the judge.
According to the alleged statement published by the Barcelona daily, the judge showed him several sponsorship contracts that he signed, but he did not remember them.
“This is something that my dad manages. And I trust him. I devote myself to playing football,” he reportedly said.
“I do what he tells me to do.”
– Panama Papers –
The income related to Messi’s image rights that was allegedly hidden includes endorsement deals with Banco Sabadell, Danone, Adidas, Pepsi-Cola, Procter & Gamble and the Kuwait Food Company.
Questions over the player’s finances increased after Messi and his father were among those named in April in reports by international media who received a vast trove of data and documents leaked from a law firm based in Panama.
The two men opened a company in Panama in June 2013, just after the allegations of tax fraud broke, to continue to hide income earned from image rights from Spanish tax authorities, Spanish news site El Espanol reported.
The Messi family acknowledged the existence of the company but they said it was “totally inactive” and never had any funds.
After winning a league and Cup double with Barcelona, the five-time World Player of the Year is due to join his Argentina teammates for the Copa America in the United States.
Argentina take on defending champions Chile in their first game of the tournament in California on Sunday, June 6.