Invoice is a document that is given to a buyer by the seller for collecting the payments. Invoice covers the total cost of the purchase or services by a buyer. Odoo sales module provides the invoicing feature.
First we should install the Odoo Sales Module.
Go to Sales Module → Configuration → Settings →Invoicing.
In the invoicing tab, we have two options;
Invoice what is ordered: Invoicing is done when the sales order is confirmed.
Invoice what is delivered: Invoicing is done when the delivery is completed.
Choosing Invoicing Policy:
When we open any product page, there we can see the sales tab. In this sales tab, we can choose the invoicing policy.