Overpaid Invoice

In the old version, a customer has overpaid of $3.00 and I have mark receive payment as -$3.00.
its showing on the invoice as Overpaid. In the customers next invoice I have marked as Account Receivable of $3.00. This has taken out 3$ from the total. What can I do to mark the old invoice as Paid not Overpaid. Thx

Have a look at Guides | Manager

It shows how to handle overpayments by customers.