Many years ago I did some contract work for a bank. Back office processing stuff.
One day I was on overdraft renewals for corporate customers. All admin really. Review the write up from the (onsite) business manager, check it was all crossed and ticked in the right places, reinput the overdraft limit, input the renewal fee (1%), press submit. I did loads, they only took 5 minutes, my eyes were going square by the end of the day.
The next morning a client was on the phone to one of the business managers screeching about fraud on a huge scale. He'd had £300k taken out of his account 😲 which had taken him £250k overdrawn. All of his payments, including all his staff salaries had bounced. Everyone was whispering, all the managers were dragged into a meeting, trying to work out how a fraudster had managed to take such a large payment and how, no one recognised the type of transaction.
Then I got called in. It was me 🤢 The day before, I'd processed the overdraft renewal. The overdraft limit was £300k, the renewal fee was £3k. I'd typed the figures in the wrong boxes - so I'd reduced the clients £300k overdraft limit to £3k and I'd charged them a £300k renewal fee 😂
The worst thing was, no one could fix it. Whilst the stupid system had allowed stupid me to charge a customer £300k, no one had the required level of authority to apply a credit of £300k...computer said no 😂😂 Not my manager, or their manager OR their manager. It took until lunchtime the next day to get hold of one of the execs in the USA, get him updated and get them to do it.
It cost them a fortune in compensation (think it was about £10k) and they had to launch a whole big risk/IT project to lock some systems down and stop it from happening again 🙈
Surprisingly they still renewed my contract for a further 3 months when it was up 😂