Oh my job was great for the cold sweats. Like, most of our customers didn't pay VAT, legitimately, as they had a thing called a VAT Exemption granted them by the government. But in order to get the computer system at Customs and Excise to recognise this you had to ensure a certain code and number was input when you submitted the details of their shipment. If you forgot, it just assumed you were liable and took the VAT! Imagine having to go to your boss and say, "You know the way [company name redacted: hah!] have a VAT exemption? Well - and now, you're really going to find this funny, I promise! - I've sort of kind of paid the VAT by accident. Hmmm? Ah, about thirty thousand Euro...."
Ah, the sleepless nights! The worst bit was when you realised A SECOND AFTER YOU HAD PUSHED SEND that you'd forgotten, and there was NOTHING you could do. The only thing you could pray for was that you had made some other error which would result in the "entry" getting "rejected", therefore not completed and allowing you to quickly insert the code before resubmitting....