Twenty one companies have applied to underwrite Japan Post's initial public offering scheduled for 2015, which market participants expect to raise almost $10 billion for the government.

State-owned Japan Post provides post office, insurance and banking services and is the country's largest savings institution.

The IPO will be the first leg of the government's plan to sell up to two-thirds of Japan Post's shares. While bankers have said the government hopes to eventually raise between 2 trillion yen and 4 trillion yen ($19 billion to $38 billion), current expectations are for the IPO to raise about 1 trillion yen.

Part of the proceeds will fund reconstruction of areas devastated by the 2011 earthquake and tsunami.

The finance ministry said that of the 21 brokerages which applied to be lead underwriters, 15 were domestic and six were foreign. It will choose six domestic and four foreign brokerages as early as September after a selection process that takes into account sales strategies and handling fees.

In addition to a national network of more than 20,000 post offices, Japan Post runs the country's biggest banking and insurance operations. It has around 176 trillion yen ($1.7 trillion) in customer saving deposits.

Financial markets are keeping a keen eye on how privatisation will affect Japan Post's investment in Japanese government bonds, although the institution has repeatedly said it will not change its investment stance in government debt.

Japan Post holds about $2 trillion in JGBs under its insurance and banking arms, making it Japan's second-largest creditor after the nation's central bank.