Let’s say that you let AP checks automatically apply credit memos and a credit memo is a applied to a wrong invoice. Maybe it should have been on hold, it’s being disputed, whatever.
Voiding the check won’t unapply the credit memo application. Frankly if you had painstakingly applied a bunch of credit memos by hand and then had to void them because of a check printing error you’d be pretty upset that they had been unapplied.
So how to you unapply this credit memo since it completely paid off the invoice? You simply void the credit memo the same way that you would void a check, with Void Historical Transactions under Purchasing.
To make it even easier, change “All” selection in the upper right to “Credit Memo”. You’ll have to re-enter and reapply the credit memo but it’s still a pretty easy fix.