Citibank says a computer glitch at its branches in Japan has caused more than a quarter of a million incorrect transactions over the past week.
In a statement, Citibank says the problem affected withdrawals and deposits made between 2 May and 8 May.
In some cases, transactions were recorded in accounts twice, while in others the transactions were processed but did not appear in statements.
The glitch affected yen savings, US dollar savings, chequeing, international loan card and advanced money accounts.
The bank says the botch-up was caused by an incorrect batch process that occured following the implementation of a new system.
In a statement Citibank says it is "taking necessary measures to prevent future occurrence".