Overpayment or Credit

I haven’t found anything on this subject since Setpember '16.
If a client overpays and just wants you to apply it to their next invoice how are you supposed to hand this?

Thanks for anyone’s help

In v5 you can create a payment for the client and apply part of it to an invoice now and keep the rest on file to apply to a future invoice.

On V4, The app create a credit with the leftover. On his next invoice, you can apply part or whole of the customer’s credit.