In a statement, the Italian Treasury said the IPO would be wrapped up in the two weeks following the actual launch of the offer. Italy, which is listing Poste Italiane as part of efforts to revive state asset sales to cut debt, hopes to raise as much as 4 billion euros ($4.42 billion) from the deal.
The IPO is also part of the government's longer-term plans to streamline public institutions and make them more competitive to support economic recovery.
Earlier on Tuesday, Poste Italiane said it had filed a request with the Milan stock market to list its shares and had asked market regulator Consob to clear its IPO prospectus.
The IPO envisages a retail and institutional offering.
The Treasury said incentives for retail investors and post office employees would be added to the prospectus in the next few weeks. Banca IMI, Bank of America-Merrill Lynch, Citigroup, Mediobanca and UniCredit are global coordinators for the share sale.
Credit Suisse, Goldman Sachs, JP Morgan, Morgan Stanley and UBS will act as book-runners.