The ABN was introduced on 1 July 2000 by John Howard's Liberal government as part of a major tax reform, which included the introduction of a GST.
The law requires each entity that carries on a business in Australia has an ABN and that the ABN appear on each tax invoice and other tax related documents issued by the entity.
[1] The Registrar registers entities, issuing them with an ABN,[2] while the Commissioner of Taxation issues the entity a tax file number.
[9] Equally, the Registrar can cancel an entity's registration and thus their ABN.
Unlike with the tax file number (TFN), the ATO has publicised the formula for checking and creating valid ABN checksums.