"Warehouse will have to wait for the invoice to be reversed (and accounting will complain);"
it is a problem of communication, not in a business
"Accounting needs to post the invoice so they can pay the customer. If they already payed it's even worse because of connections between payment and a reversed invoice...."
Users need to be more responsible for their wokr and if they found a mistake after passing all process in different departments - it s not professional!
"Which is worse? To use 122 or have a business process that doesn't work?"
Making a cancelleation - it is completely normal practice in such situations....and it tooks a few minutes.
"Much simpler then having a convoluted process where departments wait for each other constantly."
and get incorrect document history, missunderstanding of right business process in user mind
After such points of views there are becomes a lot of redundant Z developments. (Today user is lazy to make a cancellation, tomorrow he will ask for make personal transaction instead of standart.......etc)