During the incident that took place on Sept. 30, Japan's third-largest lender failed to comply with anti-money laundering procedures necessary under the foreign exchange act in transacting overseas remittances, the Nikkei said.
While checks found no evidence of illegal money remittances, the Ministry of Finance (MOF) decided on the corrective action as Mizuho is one of Japan's largest banks, with a responsibility for payment systems, the Nikkei said.
A Mizuho spokesperson and a finance ministry official in charge of the foreign exchange law both declined to comment when contacted by Reuters.
The finance ministry in August announced a three-year action plan that included tighter supervision of financial institutions in response to a report by the Financial Action Task Force (FATF), a global financial crimes watchdog.
The Sept. 30 issue at Mizuho has also triggered a response from Japan's banking regulator, which is set to issue on Friday a reprimand to the financial group over a series of system glitches, according to two sources with knowledge of the matter.
Mizuho group CEO Tatsufumi Sakai and the head of the firm's main banking unit intend to resign to take responsibility for the problems, one of the sources said.
(Reporting by Daniel Leussink, Makiko Yamazaki and Tetsushi Kajimoto; Editing by Michael Perry)