Overpayment leads to a credit balance, how to correct?

A client over paid an invoice and now has a credit balance. I need to get rid of this but don't know how. I thought about crediting one of their future invoices, but this will help them and not my problem with Quick Books online. How do I, or can I, apply the credit balance to a future invoice and also make the credit balance for this client go away in Quick Books online?