Australian Business Number

The Australian Business Number (ABN) is a unique identifier issued by the Australian Business Register (ABR) which is operated by the Australian Taxation Office (ATO). The ABN is a component of the System introduced by John Howard's Liberal government on 1 July 2000.

The Australian Business Register (ABR) is maintained by the Registrar of the ABR, who is also the Commissioner of Taxation. The Registrar registers entities and, in doing so, issues them with an ABN.

The Registrar issues ABNs only to entities who are entitled to an ABN. Entities do not have to be individuals (natural persons) or companies (legal persons). An entity can be –

For an entity to be entitled to an ABN, it must –

Whether or not an entity is carrying on an enterprise is a question of fact and there are many circumstances where an entity will be carrying on an enterprise. Without being exhaustive, an entity will be carrying on an enterprise if it –

The Registrar of the ABR can refuse an entity's application to be registered. Equally, the Registrar can cancel an entity's registration and thus their ABN. Both of these decisions are reviewable taxation decisions.

There are three ways to legally apply for an ABN:

To apply for an ABN you will need as a prerequisite a tax file number (TFN).

The ABN is an 11-digit number where the first two digits are a checksum. Unlike with the tax file number (TFN), the ATO has publicised the formula for checking and creating valid ABN checksums. Also, the nature of the ABN algorithm means that any 9-digit number can be made into a valid ABN.

In the case of companies, the ATO determines the ABN by using the company's Australian Company Number (ACN) to which the two-digit checksum is prefixed.

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