No money left the bank, but the "inputting error" came amid CEO Jane Fraser's efforts to convince regulators she's fixing the bank's controls.

In a surprising turn of events, one of the largest banks in the world, Citigroup, made a massive financial mistake. Instead of sending a small payment of $280, an employee accidentally credited a staggering $81 trillion to a customer’s account.

An employee caught the mistake quickly, but the bank has recently made other errors that have drawn scrutiny and fines from regulators.