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.

Citigroup's $81 trillion mistake sparks concerns over operational controls and regulatory oversight, prompting investments in upgrades.

Citigroup narrowly avoided what could have been one of the largest banking blunders in history after it mistakenly credited a client’s account with $81 trillion instead of the intended $280. The Financial Times reported that the error was detected only after two employees overlooked it,