|Web interface, API|
You can't remove or delete an invoice that you have created. If you have created an invoice that the customer does not have to pay due to faulty information on the invoice or for any other reason you should credit the invoice. To do this you create a credit invoice as a voucher against the invoice you wish to remove. The credit invoice will receive a new invoice number.
In order to credit an invoice you look up the invoice and select More options ➡ credit. Then you can choose to credit the entire invoice or just a part of it. You can choose if the credit invoice should be sent to the customer or not.