How to apply a customer payment to multiple invoices.
I have a great problem. I have a couple customers that receive invoices for the same amount quarterly. A couple of these customers, since they know what their invoice will be in the future will send a check, not only for this quarter but for the next 1 or 2 quarters as well. But when I apply their payment to the invoice, this invoice will show a credit balance but next quarter's invoice will show as unpaid. How can I mark the second invoice as paid or apply their payment to multiple invoices?