You can issue a one-time credit note to a customer who has an existing contract.
To do this, go to the "Customers" tab and click on the contract ID of the customer.
Go to "Perform Action" in the contract details and then choose "Manually Create Credit Note".
In the "Create Credit Note" menu you can now enter all necessary credit note information. If you wish to list several credit note positions, you can extend the credit note via "Add Row". Click on "Send" and the credit note will be sent to the customer.
billwerk will not automatically refund the amount after the credit note has been sent. If you do not carry out a refund, the credit note will be settled with the next regular invoice. If you would like to refund the amount instantly you can do so mannually. You can find instructions how to execute this here.