Currently, there is no option to treat the following scenario:

We have accounts with a -$20.00 balance, but the credit memo was “due” last month so the account goes on hold, even though it is a credit.

The same happens if the account has a total -$20.00 balance, but there is an overdue (debit balance) invoice.

It would be important to have a general Blocking rule exclusion option for the scenario when the customer has a total credit balance.