they say "it's because of the general ledger, you can't just delete things because then there is no trail." So we have to make adjustments to things we didn't actually buy or return... I was talking to my bank manager about this very problem, and what they have to go through in order to fix mistakes by his tellers. he says "I delete the mistake and re-enter it correctly."

Definitely can be a pain entering multiple entries just to correct one small thing.