ABN vs ACN: what is the difference?

ABN

An 11-digit number issued by the Australian Business Register to any entity carrying on an enterprise: sole traders, partnerships, trusts, companies, super funds and more. It's used for tax and invoicing.

ACN

A 9-digit number issued by ASIC only to companies when they are registered. It identifies the company under the Corporations Act and must appear on company documents.

How they relate

A company has both. Its ABN is usually built from its ACN with two extra digits in front. Sole traders, partnerships and most trusts have an ABN but no ACN. Each ABN record on Find My ABN shows the ACN where one exists.