Messi is appearing before a Spanish court after a complaint was lodged by a state prosecutor in June stating that he and his father Jorge tried to conceal earnings from the player's image rights.
|THE VIEW FROM SPAIN
|Pilar Suarez | Goal Spain
Messi came to the courthouse smiling as fans shouted"Messi champion! Messi for president!". The Barca fans are supporting completely him after he paid €5m back to the Spanish authorities, but non Camp Nou fans across the country are still angry about the allegation.
Both the Argentina forward and his father have denied any wrongdoing but the charges state that they hid more than €4million (£3.4m) by filing incomplete returns for the years 2006 to 2009.
"I never take care of that [tax] stuff myself and neither does my father," Messi said in July. "We have our lawyers and our wealth managers to take care of that and we trust them and they will sort this out.
"The truth is I don’t have a clue about all this and that is why we have people taking care of it."
Messi has already made a corrective payment to Spanish authorities of just over €5m (£4.2m) - the unpaid tax plus interest - and Friday's hearing will determine whether the case is pursued any further.
The Barcelona man's father was due in court first, with Messi himself scheduled to be questioned an hour later.