Australian Company Numbers

Benefits of the ACN

Under the Corporations Act 2001, every company in Australia has been issued with a unique, nine-digit number, an Australian Company Number (ACN), which must be shown on a range of documents. The purpose of the ACN is to ensure adequate identification of companies when transacting business. New companies are issued with numbers by the Australian Securities & Investments Commission (ASIC) upon registration.

The ACN is generated using an algorithm with the last digit being a check digit allowing the number to be verified.

Where the ACN must appear

A company's ACN should appear on all of its 'public documents' and 'eligible negotiable instruments' (s153). The items on which it should appear include:

  • all documents required to be lodged with ASIC
  • statements of account, including invoices
  • receipts (which are not machine-produced)
  • orders for goods and services
  • business letterheads
  • official company notices
  • cheques, promissory notes and bills of exchange, and
  • written advertisements making a specific offer which is capable of being accepted (such as by the completion of an order form).

If a company's name appears on two or more pages of a document or instrument, the ACN must be shown on the first of those pages following the company's name.

Where a number of separate companies are listed on a document (eg, a letterhead) the ACN of each should appear and in such a way that makes clear the company to which each ACN relates.

While there are no specific requirements as to how an ACN should appear on a document, it should be clear, easily readable, and obvious as to the company to which it relates.

The ACN should be identified by the words 'Australian Company Number', or by the abbreviations 'ACN' or 'A.C.N.'.

Australian Business Number

If your company has an Australian Business Number (ABN), you may use the ABN with your company's name in place of the ACN on company documents and negotiable instruments, provided that:

  • your ABN includes your nine digit ACN, and
  • the quotation of the ABN is effected in the same manner in which quotation of the ACN would normally occur. (For example, a company is required to place its ACN with its name on the first page where that name appears in a document).

For further information about the legal requirements in relation to Australian Business Numbers, contact the Australian Taxation Office.

Common seal

A company may have a common seal (s123), and then use it to execute documents in accordance with its constitution. It is not compulsory for a company to have a common seal. If a company does have a common seal, it must set out the following information:

  1. for a company that has its Australian Company Number (ACN) as its name - the company’s ACN, or
  2. otherwise:
    • the company’s name, the expression 'Australian Company Number' and the company’s ACN. or
    • if the last 9 digits of the company's ABN are the same, and in the same order, as the last 9 digits of its ACN - the expression "Australian Business Number" and the company's ABN.

ACN or A.C.N. are acceptable abbreviations for Australian Company Number. A company may make contracts and execute documents without using a seal (see s126 and s127).

Where the ACN is not required

The items on which the ACN is not required include:
  • packaging and labelling, including envelopes and transport documents
  • advertisements which do not make a specific offer which is capable of being accepted (such as advertisements which only promote the company and its goods or services in general)
  • credit cards and credit card vouchers
  • machine-generated receipts, including cash-register receipts
  • business cards and 'with compliments' slips, and
  • items which are not documents (eg, vehicles, television advertisements).


The penalty for non-compliance with the ACN provision of the Corporations Act 2001 (s153) is $1,700 or three months imprisonment, or both.

More company information

For a contents list of more information about companies and their administration, see 'Running a company'. For further information about the legal requirements in relation to Australian Company Numbers, see ASIC's Regulatory Guide 13 ACN, ARBN and company names.
This is Information Sheet 13 (INFO 13), reissued September 2013. Information sheets provide concise guidance on a specific process or compliance issue or an overview of detailed guidance.

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Last updated: 23/03/2016 03:05