On the Other Info tab, add the reason for the credit note in the Customer Reference field. Then, you can confirm the credit note. This case is for credit notes without invoices. Otherwise, you'll need to create a credit note from an invoice.

Since it is linked with ZATCA compliance, make sure that the credit note is associated to the correct original invoice or entry that needs to be reversed or corrected and also ensure that you've provided a clear reason for why the credit note is being issued.