The National Tax Agency of Japan has gathered details on 400,000 overseas bank accounts held by Japanese nationals in about 50 countries in a bid to fight fiscal evasion as only 9,000 citizens declared having an offshore account in 2016.
The tax agency will compare the two sets of information as part of its hunt for hidden assets as part of efforts to uncover assets stashed abroad, local media outlet Nikkei reports.
Japan requires anyone keeping over $446,000 (50m yen) in foreign assets to declare it.
Tokyo obtained the data this fall through its first participation in an annual international exchange designed to combat tax evasion.
In return, Japan provided roughly 50 nations and regions with information on about 90,000 accounts in the country, a source said. Parties may submit additional information later.
Japan has enhanced tax enforcement against wealthy individuals in recent years. Additional taxes totalling 4.1bn yen were imposed after a probe using data such as overseas remittances uncovered 478 cases of undeclared income and other wrongdoing during the year ended in June 2017.
Such data exchanges under the Common Reporting Standard, formed by the Organization for Economic Cooperation and Development, began last year.
The 102 current participants include British overseas territory of the Cayman Islands and Bermuda, but the US is sitting out.
Research carried out by Old Mutual International, part of Quilter, reveals that 59% of advisers say their clients have concerns about the CRS in some way.