What is an invoice number?

An invoice number is a number assigned to an invoice. An invoice number is assigned to make an invoice easier to locate and find information on. An invoice number may or may not be the same as the order number, usually not.

An order number is assigned to a purchase when it is made (such as an online order), upon shipment of the order an invoice completed (an itemized statement of the product(s)) and at this point the customer generally will refer to the "invoice" number when inquiring about their purchase.