An invoice moves through Draft, Sent, Error and Archived. Only the accounting push sets Sent; nothing else does. What each state allows:
Draft
Everything: edit a line's description, date, quantity and price, add a line, archive and unarchive lines, add a note or photo, archive or delete the invoice. A line linked to a subcontractor line asks Update linked registration? on edit and Archive linked registration too? on archive, so the two sides stay together.
Sent
Locked. Line edits and new lines are refused with The invoice cannot be edited in its current status, and the invoice cannot be deleted or archived. The only move is back to draft: Unsend in the row menu, or Change to draft on a selection.
Unsending clears the invoice number and the reference to the accounting document. The document itself is untouched: sending again creates a new document there, so tidy the old one up in the accounting system. A sent invoice is never pushed twice; pressing send on it says None of the selected invoices can be sent (already sent or archived).
Lines that still have a draft counterpart carry Counterpart sent on the other side: edits over there no longer reach this invoice. Correct the sent side by unsending it, fixing or archiving the line, and sending again.
There is no separate credit-note document in SnowManager. A credit is a line with a negative price, which any line may carry, on a customer invoice and a settlement alike: the quantity still counts work and stays above zero, so the credit is in the price. An invoice whose lines add up to below zero is an invoice with a total below zero, and it is pushed to the accounting system as an ordinary invoice, the lines keeping their sign. The charge a resolved complaint puts on a subcontractor's settlement is such a line, written for you; see How a complaint is assessed, timed and settled.
A sent invoice is still locked, so a credit goes either on the next draft for that customer or on the invoice itself after Unsend.
Error
The push was refused. The invoice shows Sending to the accounting system failed with the provider's message, usually a customer with no mapping. The invoice stays editable: fix the cause and send again. When you send several at once, each is pushed on its own, so one failure does not stop the rest: {0} invoice(s) sent, {1} failed. Failed invoices are marked with an error status.
Archived
Not billed and not sent. Unarchive it to bring it back; its work is not drafted again meanwhile.
Changing the stop behind a line
Changing a stop's Work type on the dispatch is allowed while every line drafted from it is still on a draft: the old lines are archived and new ones drafted at the new work type's price. Once any of those lines sits on an invoice that has left draft, the change is refused: The address is billed on an invoice that has been approved or sent. Correct the invoice line directly, or credit the difference with a negative line on an invoice. So fix it on the invoice: unsend it and correct the line if the stop really must follow, or leave the sent invoice alone and put the difference on a draft as a negative line. Adding or removing an extra work type on the stop follows the same rule.
Restoring a completed stop to not started removes its draft line.