You have to attach invoice to the letter about invoice.
You have to attach invoice to the letter about invoice. It is the 3rd year in a row here is a panic in our company, caused by your's (late) panic letter about out-of-date invoice, without containing invoice itself, Accountant should get invoice with the letter. There is no reason for accountant to use admin console to find invoice there and download it. The way to pay should be obvious, not go-somewhere-else-and-get-it-there way.
Also, there is no in advance letter with information about approaching time to pay. You have to make it more obvious for accountants.