Adding InvoicesInvoices are as the result of the fulfillment of an order and therefore do not exist on their own but are attached to an order.
To add an invoice, you can either:
Adding the invoice information can be either entered manually or generated from the order details. If the order details are accurate, you can click on the 'Generate Invoice from Order Data' button at the top right. If the amounts in the order include the tax, be sure to check the 'Order amounts include tax' and the taxes will be taken into account.
Below is an example of the user generating the invoice from the order data and then adding invoice number.
To set the invoice file, you must attach a copy of the invoice to the order (i.e. by uploading it as an attachment).