How do I convert an invoice to a credit note?
Login and go to Your Invoices. Filter or otherwise find the one you'd like to turn into a credit note.
Click on the invoice and you'll see a nice representation of the final invoice that is ready to be sent/was sent to your customer.
Click on the More dropdown at the top right of the invoice, and select Become credit.
We'll automatically create a credit note for you with the same information as the invoice. Easy!