The 25-year-old four-time World Player of the Year and his father Jorge Horacio were ordered by a Spanish court Thursday to appear for questioning in September as part of an investigation into alleged tax fraud.
Spanish financial crimes prosecutors filed papers with a court in Catalonia, northeastern Spain, on June 12 accusing Messi and his father of defrauding the tax office of over four million euros ($5 million, £3.4 million) in income related to the use of his image from 2006-2009.
"We firmly believe in the innocence of our client," Messi's lawyers office, Juarez Veciana, said in a statement.
"We declare that our customer will pay any amount that he is eventually found to owe but we believe that our client has already paid what he was legally obliged," it added.
If he is convicted, Messi and his father could face up to six years in prison and a hefty fine, according to Spanish media reports.
"We respect and abide by the judicial decision and we make ourselves available of the court to help resolve this matter and establish the truth.
"We trust that the judicial inquiry will resolve this matter, which leaves our client in a situation of media helplessness which we profoundly regret, in the minimum possible time," it added.
The accusations of tax fraud are a huge blow to the prestige of Messi, who has long been seen as a more humble figure than most top-class footballers -- in particular his fierce Real Madrid rival Cristiano Ronaldo.
Messi and his father aimed to deceive the state by ceding the player's image rights to companies based in tax havens such as Belize and Uruguay so they would pay no tax in Spain, according to the prosecutor's complaint filed at a court in Gava, a Mediterranean coastal town near Barcelona.
The prosecutor's complaint also alleged Messi and his father drew up deals related to his image rights in Britain and Switzerland, ensuring that the income went straight to the tax havens without any tax being paid.
The father was accused of being the brains behind the scheme, allegedly setting it up in 2005 before his son turned 18 on June 24 of that year.
The prosecutor said Messi later agreed with his father's tactics so that he would avoid any taxes on income from the use of his image rights during the period.
The income related to his image rights included contracts with FC Barcelona, Banco Sabadell, Danone, Adidas, Pepsi-Cola, Procter & Gamble and Kuwait Food Company.