ABN Registration

The Australian business number (ABN) is the identifying number that businesses use when dealing with other businesses – for example, you generally need to quote an ABN on your invoices or other documents relating to sales that you make to other businesses to avoid having an amount withheld from payments made to you. You use your ABN in certain dealings with the Tax Office and other areas of government.

You are not required to have a tax file number (TFN) to register for an ABN. However, having a TFN reduces the risk of administrative errors when dealing with the Tax Office.
Income tax exempt organisations do not require a TFN.

Entitlement to an ABN - the ATO has recently upgraded their ABN entitlement guidelines.

To be entitled to an ABN you must be:

• a company registered under corporations law in Australia
  a government entity, or
• an entity that is carrying on an enterprise in Australia.

A non-resident entity may be entitled to an ABN where:

• it is carrying on an enterprise in Australia, or
• in the course of carrying on an enterprise, it makes supplies that are connected with Australia.

Your enterprise does not have to be located in Australia.

(Source ATO)