Short answer
An ABN -- Australian Business Number -- is an 11-digit number assigned to businesses, sole traders, and other entities on the Australian Business Register (ABR). It is the main way to identify a registered entity in Australia's public business registry.
Each ABN links to a record. That record holds fields like entity name, entity type, ABN status, GST registration, and key dates. The pages on this site break down what those fields mean and flag when they change.
Who gets an ABN
Most businesses operating in Australia need an ABN. That includes companies, sole traders, partnerships, trusts, and government entities. Not-for-profits and superannuation funds may also hold one.
An ABN is separate from an ACN (Australian Company Number), which only applies to companies registered under the Corporations Act. A business can have both. For more on the difference, see ABN vs ACN.
Why it matters
The ABN is the identifier you will see across this site. Knowing what it is makes everything else easier to follow.
You can use an ABN to look up a business's public record on the Australian Business Register and check its visible ABN status. The record also shows fields like entity type and GST registration — each carrying specific meaning that guides and glossary pages on this site break down.
This site compares weekly data snapshots to detect when a record changes. The ABN is what ties each change to a specific entity. If you want to check whether a particular ABN is still active, see How to Check If an ABN Is Active.
What an ABN tells you
An ABN confirms that an entity is registered in the Australian Business Register. The attached record shows its registration status, entity type, GST registration, and key dates — enough to identify the entity and understand its public registration profile.
For deeper verification — such as financial standing or regulatory compliance — cross-reference with the Australian Business Register or the relevant government authority.