This screen shows the result of payments applied to an invoice.  Payments are actually entered using a very simple form that captures the Client, Date of Payment, Amount, and Type (cash, check). 

When a payment is entered, the Forge Ahead program applies the payment to any unpaid invoices for this client, then shows you (on a different screen) how the payment has been applied to one or more invoices.  You have the option of accepting or editing these allocations of the payment. 

If a client overpays or prepays, the program will inform you of the client's credit when you create the next invoice for them.  You then have the option of applying that credit to the new invoice.