Navigate to Network⇒Invoice⇒Credit Note

Click New

Select the relevant customer from the drop down list and then click the add button

In the pop-up window, click the search button and select the invoice that the credit note is to be created for. The rest of the information will then auto-fill from the invoice information.

Change the quality and value of the credit if required (if the original invoice was for a part that had an each price, changing the quantity will automatically change the Total) and then click Save

Press Save followed by Print or Send Email

Press Close and the newly created creit note now appears on the Credit Note List with Printed status