Lionel Messi and his father were ordered by a Spanish court yesterday to appear for questioning in September as part of an investigation into tax fraud allegations.

A court in the Mediterranean coastal town of Gava near Barcelona accepted a state prosecutor's complaint alleging that Messi and father Jorge defrauded the Spanish tax office of 4 million euros (US$5.3 million).

The Barcelona and Argentina star and his father will appear before judge Anju Deb Rani in Gava on September 17. That will form part of an investigation to determine whether there exist grounds to charge them with tax evasion.

If charged and found guilty, Messi and his father could face a fine amounting to 150 percent of the concealed earnings and 2-6 years in prison, although an out-of-court deal is another possible outcome.

Court officials said that both Messi and his father will have to appear in person for the session that will be closed to the public.

The timing of the court appearance could coincide with Barcelona's opening game in the Champions League, set to be played either on September 17 or 18.

The court accepted the complaint lodged by prosecutor Raquel Amada on June 12 accusing the pair of not paying the correct taxes from revenue earned from image rights on Messi's income tax returns from the years 2007, 2008 and 2009.

The Argentina forward has denied any wrongdoing.