If you operate a company in Australia, two numbers tend to travel together across your letterhead, invoices and contracts: the Australian Company Number (ACN) and the Australian Business Number (ABN). They are not versions of the same thing, and understanding which one does what saves time whenever you fill in a form, issue an invoice or sign an agreement.
The distinction is straightforward once you know who issues each number. According to ASIC's guidance on the Australian Company Number, an ACN is different to an ABN, which is issued by the Australian Taxation Office. The ACN is the identifier ASIC associates with a registered company. In practice, the ACN is about your legal identity as a company; the ABN is about your identity in the tax and business systems.
That difference explains why the two numbers show up in overlapping places. ASIC requires companies to display their full name and their ACN or ABN on a range of documents, which means that on many day-to-day paperwork, either number can satisfy the requirement — provided it is displayed correctly.
What each number is used for
The ACN is the number you receive through ASIC when a company is registered. It identifies that specific registered company and stays with it for the life of the company. It is the number other parties use when they want to confirm they are dealing with a particular registered entity, and it is the number ASIC's company records are organised around.
The ABN is issued by the ATO, as ASIC's ACN guidance notes. It is the identifier used in the tax and business systems, including the way a business identifies itself to other businesses, government agencies and the ATO. A registered company will normally hold both numbers, which is why both may end up on the same document.
A useful way to hold the distinction: the ACN answers "which registered company is this?" and the ABN answers "which business is this, for tax and business dealings?".
Where the numbers must appear
ASIC's guidance sets out display obligations for companies. The confirmed requirements are:
- A company must display its full name and its ACN or ABN on a range of documents.
- On documents where the details are required, the company's full name and ACN must appear on the first page.
- If several companies are listed on one document, each company's ACN must appear next to that company's name.
- The ACN or ABN must be clear and readable, and it must be obvious which company it belongs to.
- If a company uses a common seal, the seal must include the company's name, the words "Australian Company Number" and the company's ACN. Where the ACN meets the applicable rules, the seal may instead use "Australian Business Number" and the company's ABN.
Two things follow from this. First, the "or" matters: on most documents within ASIC's requirements, showing the ABN can stand in for the ACN. Second, the seal is the one place where the wording itself is prescribed — the label has to match the number you have used.
Practical read: the safest habit is to print the company's full legal name with one identifier directly beneath or beside it, on page one, in the same font size as the surrounding details. If your template lists a joint-venture partner, a trustee company and your own company, give each name its own ACN on the same line, rather than grouping numbers in a footer where the link between name and number is unclear.
Which number to put where
There is no single right answer for every situation, because the requirement depends on who is asking and what the document is for. This table is a practical reading of the confirmed rules, not a substitute for checking the specific form or authority.
| Situation | What usually works | Why |
|---|---|---|
| ASIC-required company documents (first page) | Full company name plus ACN or ABN | ASIC allows either; both must be legible and clearly linked to the name |
| Documents naming several companies | Full name plus ACN next to each name | ASIC requires each company's ACN beside its own name |
| Common seal | Company name plus "Australian Company Number" and the ACN | The seal's wording is prescribed; ABN wording is only available if the ACN rules are met |
| Forms asking specifically for an ACN | The ACN | The requester has asked for the ASIC identifier |
| Forms asking specifically for an ABN | The ABN | The requester has asked for the ATO identifier |
Where a form has a labelled field, fill the field that is labelled. Where a document is your own — a quote, an invoice, a letter — the display rules above are what govern the presentation.
Reading the rules as a checklist
Before you send a document out, it is worth running these checks:
- Is the company's full legal name present, not a shortened or trading version?
- Is the ACN or ABN on the first page?
- If more than one company appears, does each name carry its own ACN beside it?
- Is the number clear and readable — not in a faint footer, a watermark or a colour that disappears when printed?
- If a common seal is used, does the seal's wording match the number on it?
- If you have chosen to show the ABN instead of the ACN, have you confirmed that this is acceptable for that particular document and recipient?
That sixth point is the one most often skipped. ASIC's general display rule permits ACN or ABN, but a counterparty, a government agency or a financial institution may still ask for a specific one.
Questions to confirm for your own situation
The confirmed facts above come from ASIC's published guidance. Everything below depends on your circumstances and should be verified at the source:
- Which documents are in scope. ASIC refers to a "range of documents"; the current list should be read on ASIC's ACN page rather than assumed from a summary like this one.
- The exact number format. Confirm the digit structure of each identifier on ASIC's ACN guidance and the ATO's ABN material, rather than relying on memory or a template.
- Your structure. Whether your entity holds an ACN, an ABN, or both depends on how it is registered. Check this against your own ASIC and ATO records.
- Seal usage. Many companies no longer use a common seal. Whether yours does, and what it must show, is a matter for your company's records and ASIC's guidance.
- Any industry-specific or counterparty requirements. A regulator, a supply chain portal or a lender may impose display requirements beyond ASIC's.
Next steps
Gather your company's registration details and ATO records, confirm both numbers are recorded correctly, then update the templates you use most — invoice, quote, letterhead and any standard agreement. Correcting a template once is cheaper than fixing documents one at a time later.
If you are preparing identification documents as part of a property or business loan application, Australian Ltd also publishes general home loan information at /money/home-loans/, which may help you understand what paperwork is typically involved.
How to use this information
This article is general information about Australian business identifiers, based on ASIC's published guidance as at the date shown. It is not legal, tax, accounting, migration, credit or financial advice, and it does not account for your personal or business circumstances. Requirements can change, and the way they apply depends on your entity and what you are using the document for. Confirm current rules directly with ASIC and the ATO, or with a qualified adviser, before relying on any of this for a specific decision. Australian Ltd is an independent publisher; it is not a lender, a broker, a government body or a regulator.