Germany's biggest bank said an "operational error" led to the accidental collateral payment to an exchange it does business with.
The size of the mistake? $35 billion, a person familiar with the matter told CNNMoney. That's $5 billion more than Deutsche Bank's entire market value.
"The error was identified within a matter of minutes, and then rectified," a Deutsche Bank spokesman said in a statement.
Deutsche Bank said it was moving the money as collateral to its account at Eurex, a major international exchange focused on European derivatives. Investors are sometimes required to post more collateral as security for repayment. The incident occurred in late March, the person familiar with the matter said.
It's not clear how much money Deutsche Bank intended to pay -- just that it wasn't nearly $35 billion. Deutsche Bank declined to comment further.