Australian Business Number (ABN)

The ABN is an 11 digit identifier issued by the Australian Business Register. It is the canonical identifier in Australian Government procurement: it is what AusTender publishes as the supplier on every contract notice, what agencies key their supplier records on, and what must appear on a valid tax invoice. It carries a check digit, so a mistyped ABN can be detected without a lookup. An ABN tells you the entity is registered; it does not tell you the entity is registered for GST, which is a separate status you can check on ABN Lookup.