Is there a way to pay down multiple client invoices from that client’s credit balance? I can see how to do this one invoice at a time, but I’d like to be able to select all / many of the client’s unpaid invoices and say “pay these all out of the credit balance” (ie, the payments on account made that aren’t allocated to any invoices).
Unfortunately there isn’t an option for this at the moment. However, I have converted this into a feature request for you. Feature requests are regularly looked over and if there is enough support for them they may be adopted.
If you could just make supplier/client accounts simply transactional as per this feature request this would be a far better solution and would by default fix this issue.