"The Australian Business Number (ABN) enables businesses in Australia to deal with a range of government departments and agencies using a single identification number. The ABN is a public number which does not replace an organisations tax file number."
"ABN registration details become part of the Australian Business Register (ABR)"
Each ABN should equate to a single 'business structure', although that structure may be used to carry out a range of business activities. A range of kinds of entity are issued ABNs, including individuals, corporations, partnerships, unincorporated associations, trusts and superannuation funds. Entities must be carrying on a business in or connection to Australia to receive an ABN.