Small business-Australian company numbers

On registration, your company will be issued with a unique nine-digit Australian Company Number (ACN). This ACN must be shown on your company documents to ensure identification of your company when transacting business.

The ACN should appear on all of your company’s 'public documents' and 'eligible negotiable instruments'. These include all documents that are lodged with ASIC, orders for goods and services, business letterheads, cheques, and written advertisements making a specific offer capable of being accepted.

The ACN should be clear, easily readable and obvious as to the company to which it relates.

Australian Business Number

If your company has an Australian Business Number (ABN), you may use this with your company's name instead of the ACN, provided that your ABN includes the nine-digit ACN and the ABN is quoted in the same way that the ACN would be. For further information about the legal requirements regarding ABNs, contact the Australian Taxation Office.

Common seal

A company may have a common seal and use it to execute documents (but it is not compulsory). Companies may execute contracts and documents without it. If a company does have a common seal, it must include certain information including the company's name and the ACN (or ABN).

Where the ACN is not required

There are certain items where the ACN is not required, including packages and labels (including envelopes), advertisements that don't make a specific offer capable of acceptance (such as advertisements that promote the company and its goods and services in general), credit cards and vouchers, cash-register receipts, business cards and 'with compliments' slips.


The penalty for failing to comply with the ACN provision of the Corporations Act 2001 (s153) is a fine, three months imprisonment, or both.

More about this topic

Members of a company

Starting a company

Are you allowed to operate a business?

Corporate key

Registering a business name

What is a company?

Appointing alternate directors

Minimum officeholders

Shares and the share register

More information on the ASIC website

Australian company numbers - INFO 13

ACN, ARBN and company names - Regulatory Guide 13


More about small business

Small business home

Starting a small business

Compliance for small business

Closing a small business


Last updated: 04/11/2013 12:00