Simple Invoice Software


An invoice number is a special sequential code that is allocated to invoices. Assigning invoice numbers is amongst the most important parts of invoicing, because the invoice numbers ensure the appropriate documentation for accounting, audit and tax purposes.

invoice number Additionally, they assist making the process of tracking payments easier and quicker and can be used as an identifier during any conversation with a customer. The customer just needs to state the invoice number and instantly you will be able to find the invoice and resolve any queries that the customer might have.

Bear in mind that without an invoice number, an invoice is not regarded as a legal binding document.

How to assign invoice numbers

Before we get into the different methods of allocating invoice numbers, here are some important points to note: Bearing the above in mind, let’s look at the various ways to allocate invoice numbers:

Simple system

This involves assigning each invoice with basic numbers – 1, 2, 3 and so on. You could also use - 01, 02, 03 or 001, 002, 003. This invoicing system is as straightforward as it appears and this system is advisable to be used for business owners with a small database of clients.

Leading zeros invoice system

This invoice system uses numbers that begin with multiple zeros such as- 00000000001, 000000000015, 000000000023 and so on. This leading zeros system is great to use if your book-keeping practices are somewhat standardized.

Year based system

In this system, number invoices are assigned with the prefix of year of issuance. For instance – 2020-1, 2020-2, 2020-3, and so on. When a new year begins, the year prefix changes and you’d have – 2021-1, 2021-2, 2021-3 etc. Using this system lets you immediately see what year the invoice was/is issued. It helps you keep your records organized while still following the requirement for sequential numbers.

Year and month based system

This is similar to the year based system except in this case, the month is also added as a prefix. This is what your invoice sequence would look like for January as an example- 2020-01-1, 2020-01-2, 2020-01-3, for February- 2020-02-1, 2020-02-2, 2020-02-3, for December- 2020-12-1, 2020-12-2, 2020-12-3. This system offers the same benefit as the year-based one in terms of organization. It may even have an edge over the latter as it shows you not only the year but month as well. It is also preferable to use in situations where the number of invoices is large.

The three systems stated above are the standard invoice numbering systems any business owner can utilize for their invoice documents.

However, there are other methods that can be applied:

Invoice numbers and recurring invoices

In the case of recurring and frequent invoices, it is advisable to use a different numeration or numbering pattern with a suffix. The assigned invoice number could be something like this- 2020-1-M, where “-M” is the suffix. Numbering recurring invoices in this manner helps ease the process of managing as well as keeping track of such invoices.

Invoice number prefix and suffix

Invoice numbers can have prefixes and suffixes. In this case when you issue a new invoice you need to increment just the primary part. For example: AA-21-MTX, AA-22-MTX etc. where "AA-" would be the prefix, "21" is the primary part and "-MTX" is the suffix.

Invoice numbers with Inv24 invoicing software

Our software offers and provides the best invoicing numbering. We efficiently assign invoice numbers via our smart automatic numeration system. We ensure that your invoice meets the top standard while being as personalized as you need it to be. Sign up with us for free today!

Our simple invoice software Inv24

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