ABN vs ACN: what's the difference?

Both numbers identify a business, but they come from different registers and mean different things. In short: an ABN identifies a business for tax and trading; an ACN identifies a company as a legal entity.

ABN — Australian Business Number

• 11 digits, issued by the Australian Business Register (ABR).
• Held by any business type — sole traders, partnerships, trusts and companies.
• Used for invoicing, GST, and dealing with government and other businesses.

ACN — Australian Company Number

• 9 digits, issued by ASIC when a company is registered.
• Held only by companies (entities with “Pty Ltd” or “Ltd” in the name).
• Identifies the company as a legal person, separate from its owners.

How they relate

A company has both, and they're linked: its ABN is simply its ACN with a two-digit prefix. So the last nine digits of a company's ABN are its ACN. A sole trader or partnership has an ABN but no ACN, because there's no company to register.

Example: a company with ACN 004 085 616 might have ABN 53 004 085 616 — same nine digits, plus a checksum prefix.

Which one do I use?

• Invoices, quotes, GST, tax → ABN.
• Company registrations, ASIC filings, legal documents → ACN.
• Checking whether a business exists and is active → ABN (it covers all entity types).

Verifying either number

To confirm an ABN is real and active, do a direct ABN lookup. Because a company's ABN contains its ACN, an ABN lookup also tells you the company behind an ACN — search the entity name in the directory if you only have the company name. For a full verification workflow, see how to verify an Australian business, or start with how to look up an ABN.