The Argentina international began court hearings on Friday, to answer allegations over unpaid tax on money from his image rights.
Reports have suggested that Messi used countries outside of Spain to sell his image rights, and avoiding Spanish tax laws.
His father, Jorge, has also been implicated in the case and he too appeared in a separate hearing to his son.
Both men have strenuously denied the charges, which were originally levied against the pair by the Economic Crimes Prosecutor Barcelona in June.
And the pair's legal representative, Cristobal Martell, said Friday's proceedings are an opportunity for the Messi family to cooperate with Spanish authorities in an attempt to clear their name.
"To start a procedure like this we are following just one instruction, to cooperate with the administration to explain my client's actions and provide them with financial information," Martell commented.
"The instruction from the Messi family has been to be transparent, clear and cooperative.
"In terms of transparency, the hearings began today and we have provided evidence to show a complete unwillingness [by my client] to commit fraud, a strong effort to be transparent for the tax office, and a desire to avoid entering into any kind of bitter fight with the State about these matters."
