Member dragonfiddle asked last year how to close-out an invoice that had been partially paid. But, the topic was archived (read-only) and never resolved. I had the same concern, stumbled onto a solution, but could not respond directly. So, here it is.
To close-out my invoice, I unchecked the "Allow Partial Payment" option, increased the discount enough to negate the remaining balance, and then selected "Send Update". After I did this, warning messages appeared. I didn't understand what the messages were saying, but took it to mean that the update could not be sent. Although I presumed the changes would not be kept either, they actually were. I selected "Manage Invoices", looked for the same invoice, and it now showed as "Paid".
I hope this helps someone looking for a similar resolve to outstanding invoices.
--David
