Australia Business Numbers (ABN) and Australia Company Numbers (ACN) uniquely identify businesses within the country.

The ABN is a unique 11-digit identifying number that businesses use when dealing with other businesses. A company's ABN frequently includes the ACN as the last nine digits. The ABN indicates that a person, trust or company is registered with the Australian Business Register (ABR).

An Australian Company Number (usually shortened to ACN) is a unique 9-digit number issued by the Australian Securities and Investments Commission (ASIC) to every company registered under the Commonwealth Corporations Act 2001 as an identifier. The number is usually printed in three groups of three digits.

Companies are required to disclose their ACN on:

the common seal (if any)

every public document issued, signed or published by, or on behalf of, the company

every eligible negotiable instrument issued, signed or published by, or on behalf of, the company

all documents required to be lodged with ASIC

This regulation uses the content blades titled Australia Business Number or Australia Company Number.