Grasser accuses Peter Haunold of wrongly advising him. Haunold and Deloitte deny the charges and claim that Grasser did not follow their advice.
The former finance minister owes the sum of €2.4 million in back-taxes.
Grasser is alleged to have dodged taxes by transferring money to foundations in Liechtenstein, Cyprus and elsewhere. His fees as a consultant to the wealthy Meinl consortium (amounting to €9 million), and a half-million euro sum invested by him are under scrutiny.
He said that as far as he knew he had been paying the correct tax on his assets and if not, it was because Haunold had misinformed him. "No step that I took was without his approval," Grasser told the ORF state broadcaster.
The Austrian Press Agency reported that Grasser appeared tanned and “good humoured” in court.
The hearing should have taken place three months ago but Grasser became ill whilst on holiday in Capri and had to postpone it - causing a media storm when photographs of him looking relaxed and well were published in the press. A local pediatrician diagnosed him as suffering from a chest infection and Grasser has refused to allow his medical records to be made public.
The hearing is likely to last for three days. Grasser’s wife, the socialite Fiona Pacifico Griffini-Grasser, and the banker Julius Meinl will appear as witnesses.
Grasser could face a €15 million fine and, in the worst case, a prison sentence - if he fails to prove that Haunold was at fault.