Japan Post Holdings Co. and its banking and insurance arms will officially file with the Tokyo Stock Exchange as early as late June for approval of their simultaneous listing in October, sources close to the matter said Monday.

The Tokyo bourse will approve one of the biggest stock listings in Japan possibly in late August to launch the final stage of postal system privatization started under a reform law enacted in 2005 under Prime Minister Junichiro Koizumi.

The initial public offering for the three entities is expected to total ¥1 trillion to ¥2 trillion, bringing their total market capitalization to some ¥10 trillion, the most since the ¥8.8 trillion for NTT Docomo Inc. upon its IPO in 1998, stock market sources said.