The Finance Ministry will on Friday start to send out letters to some 15,000 Greeks who were found to have moved money abroad without declaring it to local tax authorities.
Some 5 billion euros was not declared, the authorities have said, and the government hopes to collect 2.25 billion euros from the 15,000 depositors.
The depositors will be asked to submit an additional declaration of assets within three weeks of receiving the ministry request.
Depositors who question the Finance Ministry data will have to provide evidence that their money has already been taxed.
Greece's international rescue creditors have been pressing the debt-hit state for two years to reform its ailing tax system, citing poor collection as a key factor keeping the country mired in crisis.
Financial prosecutors Grigoris Peponis and Spyros Mouzakitis were expected to receive this week the original version of data relating to some 2,000 Greeks with accounts in the Geneva branch of HSBC before deciding whether charges should be pressed against any of those on the list.