What is an Invoice Number?

Definition: An invoice number is a unique, sequentially-organized, number assigned to each invoice being issued. In other words, it is a numeric series that organizes invoice

What Does Invoice Number Mean?

Invoice numbers have many different purposes, the main ones being accounting and tracking requirements. Once an invoice is issued the company has to record the invoice as revenue, by having unique invoice numbers the company can track them more easily to ensure the invoice gets paid by the client. These numbers are also useful for administrative computer-based systems because they allow the system to identify each invoice and by having an exclusive identification they can attach the invoice content to many other elements to consult them so the system can provide different reports to company administrators.

In some countries these sequential numbers are regularized by established procedures set by tax law enforcement agencies and, in some other cases, these institutions provide a nomenclature for the number so they can be standardized. On the other hand, these numbers are very much required for accounting purposes, by using them accountants can make sure that invoices are not recorded twice.

Let’s take a look at this example.


National Furnitures Co. is a company that produces work stations for businesses. The company has been in business for some years and they have a very automated sales process. One of their sales representatives got a call from a client asking if the last invoice he received was already paid for; the client didn’t remember if he sent the check or not. The sales person called the Collections department of the company to find out if the invoice was paid or not. Is an invoice number useful for this situation?

An invoice number, as we discussed, is a unique number that identifies each invoice. By using the company’s computer-based administrative system the analyst can locate the client’s account and the invoice number to review if a payment was received for that invoice.