As for the issue with creating a CN from history that was assigned to an account that no longer exists, do I select "edit new items on documents" under file/options? If this box is ticked, will this cause the error to occur before the CN is posted in Invoicing?

I should have clarified that in the other issue with being able to post the invoice with no account code assigned only happens when we use our MISC item code that lets us pick which account we want it to go to. I still don't understand how the subledger can let you post when part of the entry isn't assigned to a GL account.