backend order creation
Creating an invoice for an order moves it to a state in which it cannot be canceled or changed. A new invoice page looks similar to a completed order, with some additional fields. Every activity that is related to an order is noted in the Comments section of the invoice.
Normally, orders are invoiced and captured when the shipping process starts. If the method of payment is a purchase order, or if the payment action is set to Authorize and Capture, the order will be invoiced and payment is captured during checkout. You can generate an invoice with a packing slip, and also print shipping labels from your carrier account.
When the state of new orders is set to Processing, the option to Automatically Invoice All Items becomes available in the configuration. Some credit card payment methods complete the invoicing step as part of the process when the payment action is set to Authorize and Capture. In such a case, the Invoice button does not appear, and the order is ready to ship.
You must generate an invoice for an order before you can print it.