Marcel Bruehwiler was charged for "criminal organisation, laundering, illegal exercise of the profession of a financial intermediary in Belgium and serious organised tax fraud," said the state prosecutor's office in a statement.
The investigating magistrate released Bruehwiler, who denies all charges, after several hours of interrogation and said he would examine documents seized from the bank's premises in Belgium.
Belgium's prosecutors allege that UBS has been working over the last decade to get wealthy Belgians to hide "several billions of euros" in accounts in Switzerland.
"Preliminary elements of the investigation show organised plans that probably allowed tax fraud," said Ine Van Wymersch, a spokeswoman for the state prosecutor.
She added that incriminating information was obtained "through very precise accusations made by the compliance officers who have either quit the bank or who have been fired."
After three months of investigations, police searched the home of the bank's chief and that of a client, she said.
The newspaper L'Echo said separately that UBS Belgium had helped wealthy clients move large sums of money to the bank's home base in Switzerland to avoid paying tax.
On Thursday UBS said in a statement that it fully respected the law and would tolerate "no activity meant to allow any client to get around their tax obligations."
It added: "UBS is cooperating fully with the Belgian authorities."
The bank is currently under investigation in France and Germany on similar charges. In 2009 it paid $780 million (696 million francs) in fines and had to hand over the names of several thousand US clients to American authorities in a massive tax evasion probe.
UBS and many of its global peers have been rocked over the past few years by scandals over tax fraud, money laundering and rigging of key financial markets, leading to billions in fines.