Telling the truth about SME life today

What Is An Invoice Number & Why Are They Important?

What Is An Invoice Number & Why Are They Important

Invoice numbers are a series of unique, sequential identifiers which are included on every invoice a business sends, whether big or small. These numbers help in keeping track of sales and purchases, provide proof of payment made between two entities and ensure accuracy and credibility of financial records for tax payment processing.

Let us look at what invoice numbers are and why their correct usage on financial transactions can ensure smooth internal and external tax and accounting operations.

What Is An Invoice Number?

The combination of letters or numbers on top of an invoice or bill is an invoice number. It is a unique identifier which makes it easy to recognise and trace them within accounting databases. The invoice numbering system of each organisation is also different.

Invoice numbers are used to keep track of the invoice and also provide proof of payment. This holds the business accountable for the transactions they make with customers on the goods and services they provide.

These days, invoice number generation is most likely an automatic process through an accounting system like Quickbooks, Sage or Xero. The number will be populated and added to the invoice based on the template that you have set up. Businesses which manually create an invoice, should accurately assign the next sequential invoice number that follows the latest invoice sent to ensure accurate financial records.

Why Are Invoice Numbers Important For Your Business?

  • invoice numbers help you to monitor finances
  • invoice numbers provide accountability & evidence of transactions

Invoices are a security blanket for both the buyer and seller since they provide proof of a transaction made and holds both the parties accountable. They also help in streamlining bookkeeping and makes organisation of records easy.

All in all, a good invoicing system makes financial tracking easier and gives a business peace of mind. Without such a system, tracking of order details, transactions and even buyer details would be a hassle and might affect the financial record of a company.

How Do You Create An Invoice Number For Your Business Invoices?

The easiest and most common way of generating invoice numbers is by sequential numbering. In this, each invoice will have a numeric sequence starting with one and each new invoice sequentially adds one to the number each time another transaction is made.

Many businesses also incorporate their business details like name or initials within the invoice to avoid confusion. For example, an invoice number “ABC-2024-0001” could indicate ABC company’s first invoice of 2024. This system makes it easier for customers to refer to past payments while allowing them to distinguish between invoices of various businesses.

By creating and maintaining your business’ unique invoice numbers, you can avoid discrepancies quickly and ensure timely payments.

An invoice can be manually assigned or automatically. While an automatic numbering system is much more accurate and saves time, each invoice should be personally reviewed before sending on to customers to ensure that the sequencing and information held on it is correct.

Examples Of Invoice Numbering Systems

Although there is no explicit guideline or regulation set out by financial organisations for numbering the invoice, a business invoicing system must be coherent and reliable, whether manual or automatic.

Common sequencing patterns are shown below and can be used to create a helpful invoice numbering system:

  • Company initials are great to be utilised as identifiers for invoices. This method helps distinguish one business invoice from another and avoids confusion. For example, a company named Auto Invoicing Services can use the acronym AIS followed by an invoice number like AIS-0030- indicating the 30th invoice they issued.
  • Even clients and other businesses which do regular business with you can be numbered. This ensures efficient bookkeeping. For example, the first invoice of a client with designated number 422 can be written as 422-0001.
  • Another helpful system of invoicing can be to include the date of issue in invoice number. For example, invoices issued on 1st January 2024 (mm/dd/yyyy format) can use a sequence like 01012024-0001, representing first the date and then the number of invoice given out that day.

A consecutive invoice sequence is always the best no matter what system you use or best suits the business. Start with 0001 and move up from there to keep things simple.

What Happens If You Don’t Include An Invoice Number On Your Invoices?

Multiple complications can arise if an invoice number isn’t included on an invoice. One major problem is the difficulty in tracking payments or ongoing accounts which can lead to late or incorrect payments. The trust between a business and its customers is also harmed as a disorderly payment system and lack of correct invoices can indicate a lack of professionalism.

Businesses without invoice numbers may face issues with its customers and when it comes to tax reporting to HMRC, this will also be difficult without accurate invoicing systems in place. Being unable to issue accurate tax documents may bring the business under investigation or stricter surveillance by HMRC in later tax reporting years. It’s therefore very important to keep a unique and accurate invoicing system for your business so that transactions remain secure, transparent and trackable.

Benefits Of Invoice Numbers

Invoice numbers are integral for any business’ financial operations and bring with them a number of benefits.

  • Tracking of payments is made easier which further provides transparency and accountability.
  • Easily tracked payments save time when monitoring money in and out of the company
  • By carefully managing their invoicing, businesses can make informed and efficient decisions regarding finances and be tax compliant.
  • Invoice numbers are an essential accounting tool which makes monitoring payments easy.
  • A sequential numbering system can help a business quickly search for invoices sent to customers and other businesses and ensure proper tracking of accounts receivable.
  • An automatic numbering system helps streamline the payment process and lessens the probability of mistakes. With this, a business need not manually assign invoice numbers but use a software program to do so. It saves time and effort in the long run.
  • Customer experience is improved if invoicing numbers are well managed. This is so because in case of disputes or issues, invoices can be easily tracked and referenced. Customers feel more trust and confidence in businesses if their invoice systems are reliable and secure.
  • With a consistent numbering system, a business can easily avoid duplicate payments. Customers can quickly identify duplicate invoices from the same vendor and avoid making double payments to them..
  • Tax reporting is an easier process with a proper invoice numbering system. Invoices act as a primary source of income documentation and if they’re accurately numbered, a business can ensure its compliance with government and tax regulations.

Can You Use The Same Invoice Number If The Invoice Is Cancelled?

As a rule of thumb, no, the same invoice number should not be used more than once. If an invoice is cancelled, a credit note should be issued but the invoice number should not be reassigned. To prevent unexplained gaps in invoice number sequencing, never just delete an invoice number if the transaction against it is cancelled. A credit note can be issued against the original invoice number of the same amount to remove a transaction. It not only cancels the original invoice but also ensures the system is intact.

Can You Change An Invoice Numbering System?

An invoice numbering system can definitely be changed if necessary but it should be done in a way that doesn’t disrupt the sequence of invoices. After changes are made, all invoices must maintain a consecutive numbering pattern. It is good practice to keep detailed records of previous systems used, should there be any questions asked during audits in the future.

It is advisable to wait for the next accounting period to start a new invoice numbering system/series. By doing this, you have a clear start/end point for the varying systems which should help to avoid mistakes of confusion if changing things up mid-year.

One thing to keep in mind while modifying invoice numbering sequences is to avoid repetition or skipping of numbers. For example, ‘023’ of the last invoice number should be replaced with ‘024’ in the newer one, like, ‘21/INV/024’ or ‘2020-024’.

Where Should Invoice Numbers Go On An Invoice?

Although they can be put anywhere, the most common place to put invoice numbers is at the top of the invoice or the bottom right of the page. In the former, it’s close to the company details and in the latter, it’s along with the payment terms and details. This helps the customers to identify them easily and keep track of payments.

Invoice numbers can also be included in the email subject line if a business sends online invoices to their customers. This system can be automated with softwares such as Quickbooks, Sage, Xero etc.

How Are Invoice Numbers Related To Tax Reporting?

Invoice numbers are essential for the financial aspect of a business as they allow for accurate tax reporting to generate tax documents and to stay compliant with government regulations. The total amount of sales can be determined by using the sum amount of invoices sent.

Apart from tax purposes, invoice numbers are used to maintain an optimised record of incoming and outgoing expenses. Discrepancies and mistakes while filing taxes can be easily checked if a solid sequencing system is in place. It can also highlight financial trends in business income over a period of time.

Invoice numbers help provide accountability, proof of transactions made, up-to-date and accurate bookkeeping records and help a business be compliant to financial bodies.

Tips For Keeping Track Of Your Businesses Invoices

  • Invoices should be clearly and accurately labelled when created.
  • Invoice numbers should be visible on all customer-facing documents like invoice, receipts.
  • Automated numbering sequence should be double checked to ensure accuracy
  • Backups of invoices should be maintained in case of human or technical errors in numbering sequence.
  • Ensure your staff are aware of the importance of invoice numbers and how to correctly assign them.

By following these tips and implementing a solid numbering system for your invoices, you can easily track payments, monitor finances more closely, and stay organised with your company’s financial records. This will help ensure smooth processes between buyers and sellers while also providing clear accountability.

How Can You Track Payments Received Against Specific Invoices?

Payment tracking and recording can be a tedious task if done manually but there are many financial programs that can turn this into an efficient and smooth process.

Automation in accounting and tracking the transactions within it can save time and resources for the business and allow you to prioritise more important tasks. Software which can record invoice numbers, dates of issuing and receiving, and other relevant information in a searchable database is nearly always a worthwhile business investment.


This article has explained what an invoice number is and why it’s important. To recap, an invoice documents a transaction between two parties and each invoice sent out by a business must have a unique number assigned to it. These numbers are important as they keep record of financial transactions and provide accountability and proof of them.

Whichever method you choose to assign and manage your invoices, it’s an important business administration and finance step that needs to be decided to make tax filing efficient and in line with reporting regulations.



Related Stories

More From

Most Read


If you enjoyed this article,
why not join our newsletter?

We promise only quality content, tailored to suit what our readers like to see!