Adagio Invoices easily creates a credit note from an invoice in history. The Job remains assigned.
The debit is posted to the Billings account.

However, Job Cost treats the transaction as "Other Charges" instead of "Billings" so recognition of revenue and expense is not done and the amount remains in the Billings account forevermore. Also the Job totals are off.

Credit Notes should by default be "Billings".

It would also be nice if something would be brought in to the reference and description fields of Billing transactions - like the invoice number - so that looking at a Job Status report one could see not just the amount of a transaction but also a way to identify it.