The Australian business number (ABN) is a single business identifier that allows businesses to deal with the Australian Taxation Office (ATO) and other government departments and agencies with one identifier.
An ABN is not compulsory and not everyone is entitled to an ABN. The following entities will need an ABN to comply with other tax obligations:
Other eligible entities may choose to register for an ABN:
If an entity makes supplies of goods or services to a business, the supplier entity generally needs to quote an ABN. If the supplier does not quote an ABN, the payer may need to withhold tax from the payment.