User wants to show the clients how much they paid (partially) and how much they owe (outstanding) on the invoices. How does the user show paid and outstanding amounts on invoices in CORE?
CORE follows the GAAP accounting rules and so keeps the original invoice intact. The partial payments are reflected on the next invoice if you enable the Account Summary option (selected by default).
Also, the best and easiest way to show these amounts on an invoice is to print statements and send those to the clients. From the Statements screen, you can easily preview and email project and client statements. Check Statements for details.