In a traditional meaning, an invoice is a time-stamped document that has items on it and records a transaction. It's an invitation to pay for services or goods between a supplier (or seller) and a customer.
Thinking about an invoice in a traditional sense you might be thinking about the end result, the document that is distributed to the customer.
In Younium the printed invoice is the end result. It is generated from the invoice section of the service. That section holds invoice lines that are fetched from the order object. We have done it that way to create flexibility on how to calculate invoices and credits of invoices generated from the order.
When creating an invoice from the order the invoice object is then generated. That is still in the draft stage. To actually execute the transaction of an invoice that will not only generate the printed copy of the invoice but also generate transaction records in your journals the Invoice must be posted.
The action of posting an invoice is not possible to undo. It has generated transactions both in Younium and in your accounting journals. If you want to correct information on an invoice or to stop your supplier-customer relation and not expect a distributed payment to be paid - That invoice needs to be settled against a credit invoice.