Thank you, but that isn't what I need to do. They applied credits to open invoices and we didn't know so we paid them with a check. Now, since we took the credits twice, I need to record a debit memo to show that we owe the money. I assumed it would just be entering a bill, but my boss says no. That it has to be a debit memo. I can't find anything on how to do this.
We'll notify the previous reply by my colleague to update the answer.
For this, if the Invoice(Bill) from your Vendor has already marked as paid. For the Credit given by your Vendor, just create a Vendor Credit. So the Balance will show a Negative Value which can be applied to the next Purchase/Bill.
Go to the +New button, select Vendor Credit.
From the Vendor Credit window, choose the vendor who issued the credit.
Enter the date of the credit.
Put the credit amount.
In the Account Details section, select the account used in the original section.