Bonlat's assets were said to include a $4.621bn Bank of America account, which did not exist.
The Bonlat account was at the core of the discovery of Parmalat's troubles, after Bank of America disavowed any knowledge of the alleged account.
Mr Tanzi's defence, according to BBC Rome correspondent David Wiley, "is that he stole no money, merely kept on covering up a worsening financial situation which he hid from shareholders".
The company's shares, meanwhile, have been suspended from trading on the Italian stock market.
Obligations
Parmalat itself is being run by an Italian government-appointed rescue administrator, so it can continue operations and pay its suppliers.
Among them are Italian dairy farmers, to whom the firm owes some 120m euros.
Parmalat, which employs 36,000 people worldwide, will also now be able to put financial creditors on hold, while it draws up a recovery plan within six months and two teams of Italian investigators probe its books.
Recent reports also suggest that Fausto Tonna, Parmalat's former chief financial officer, has told Italian investigators that the fraud dates back until the late 1980s.
'Europe's Enron'
The scandal at Parmalat, now dubbed "Europe's Enron" after the downed American energy giant, could also have grave implications for the company's auditors, the Italian branch of accountancy firm Grant Thornton.
Parmalat's troubles leave Italian farmers in the lurch
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According to reports, the international head of Grant Thornton has ordered an internal investigation into the affair.
The accountancy firm has been auditor to Parmalat or some of its main subsidiaries since 1990.
Grant Thornton has so far insisted that its staff have acted correctly, and that the fake document has made them a victim of fraud as well.
Regulatory failure?
Questions have also been raised about how Italy's financial regulators could have missed the problems at Parmalat.
Italy has also been forced to call on the European Union to waive its rules on state aid to prevent Parmalat's woe from creating a wider dairy sector crisis.
The government is primarily concerned to minimise any wider fall-out from Parmalat, which plays a crucial role as Italy's biggest food company, purchasing 8% of the country's milk production.