Australia ABN Checker (Business Number & GST Registration)
Is this ABN well formed? Checked in your browser — then one click to ABN Lookup.
Paste an ABN to check its 11 digits with the Australian Business Register’s modulus 89 method. Nothing is sent anywhere. Tax File Numbers are confidential and are not checked here.
Who is it, and is it registered for GST?
A valid format does not show that the ABN is active or whose it is. ABN Lookup, the Australian Business Register’s free search, shows the entity name, ABN status, entity type, GST registration and main business location.
Opens the ABR’s site in a new tab. The ABN is sent to it only when you click.
If it is a company’s ACN
Do not search with a Tax File Number: TFNs are confidential.
The ABR’s calculation
| Position | Digit | Digit used | Weight | Product |
|---|
Subtract 1 from the first digit, multiply each digit by its weight, add the products and divide by 89: a remainder of 0 means a valid ABN.
Results
| Line | Number and reason | Result |
|---|
About the Australia ABN Checker (Business Number & GST Registration)
An Australian Business Number (ABN) is the 11-digit number issued to every entity registered in the Australian Business Register (ABR) — the number a business puts on its invoices, quotes and receipts. It is a 9-digit identifier with two check digits in front, worked out with a modulus 89 calculation, so a mistyped ABN can be caught before you pay a supplier or send an invoice.
Paste an ABN — with or without spaces, or with “ABN:” in front — and the checker applies the ABR’s own method in your browser, shows every step and explains exactly why a number fails. Paste a whole column from a spreadsheet to check a supplier list at once. A pass means the number is well formed; to see who it belongs to, whether it is active and whether it is registered for GST, open it on the ABR’s free ABN Lookup with one click. The checker itself never looks numbers up or stores them.
How to use it
- Type or paste an ABN. Spaces, hyphens and dashes, an “ABN” label, full-width digits and the invisible characters copied text can carry are all fine.
- Read the result: Valid ABN with the ABR’s calculation, or the reason it fails — the wrong number of digits, a letter where a digit belongs, a leading 0, or check digits that do not match.
- For a valid ABN, open it on ABN Lookup to see the entity name, ABN status and GST registration.
- To check many, paste one per line or whole rows from a spreadsheet: the ABN on each line is picked out. Show only the problems, copy the valid ABNs or download a CSV report.
Examples
51 824 753 556
Valid ABN (5−1)×10 + 1×1 + 8×3 + 2×5 + 4×7 + 7×9 + 5×11 + 3×13 + 5×15 + 5×17 + 6×19 = 534 = 6 × 89
It is the Australian Taxation Office’s own ABN on ABN Lookup.
51 824 753 557
Not a valid ABN: the weighted total is 553, which leaves 19 when divided by 89
15 824 753 556
Not a valid ABN: the weighted total is 498, which leaves 53 when divided by 89
004 028 077
Not an ABN: 9 digits, so perhaps an ACN An ABN built on this ACN would be 49 004 028 077
ABN Lookup shows 49 004 028 077 as BHP Group Limited’s ABN.
51 824 753 55O
Not a valid ABN: an ABN has only digits
Common uses
- Checking the ABN on a supplier’s invoice before you pay it.
- Cleaning up the ABNs in a supplier or customer list.
- Making sure your own ABN is printed correctly on invoices, quotes and your website.
- Testing an ABN field in a form or an accounting system against the ABR’s method.
How the ABN check works
The ABR publishes the method on its Format of the ABN page:
- Subtract 1 from the first (left-most) digit.
- Multiply each of the 11 digits by its weight: 10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19.
- Add up the 11 products.
- Divide the total by 89. If the remainder is zero, the ABN is valid.
Because 89 is a prime number, larger than every weight and every difference between two of the (all different) weights, the check catches every single mistyped digit and every swap of two digits. It cannot catch every combination of two or more mistakes, and a made-up number with the right check digits passes too.
What a valid result does — and does not — tell you
A valid result means the number is well formed, so it was probably copied correctly. It does not show that the ABN is active, who it belongs to or whether the business is registered for GST. ABN Lookup shows each ABN’s entity name, ABN status, entity type, GST registration and main business location; the checker’s Open on ABN Lookup button takes you straight to it. Before paying a new supplier, check that the name on ABN Lookup matches the business you are dealing with.
ABN, ACN and TFN
- ACN (Australian Company Number): the 9-digit number ASIC gives every company. ASIC notes that a company’s ABN is often the same as its ACN with 2 extra digits at the beginning, and that a company can then show its ABN where it would show its ACN. For a 9-digit number the checker shows the ABN those two check digits would give — confirm it on ABN Lookup. ASIC: Australian Company Number.
- TFN (Tax File Number): confidential. Under the Privacy (Tax File Number) Rule 2015, organisations may ask for a TFN only for a purpose authorised by taxation, personal assistance or superannuation law, and must tell you that declining to quote it is not an offence. This checker never checks TFNs — do not type yours here, or into any website that does not need it.
Checking a supplier list
Copy the ABN column (or whole rows) from a spreadsheet or your accounting software and paste it in. Each line’s ABN is picked out — a line with a phone number as well as an ABN still finds the ABN — and repeated ABNs are flagged. The CSV report lists every number with its result, the reason for any failure and an ABN Lookup link for each valid one, so you can confirm the names and GST registration of the suppliers you pay.
Limitations
- An offline format check: it cannot tell whether an ABN is active or cancelled, who holds it or whether it is registered for GST — ABN Lookup shows that.
- A made-up number with correct check digits passes, and so does a cancelled ABN.
- The ACN’s own check digit and Tax File Numbers are not checked.
- Up to 10,000 numbers at a time; the table shows the first 500, and the CSV report has them all.
Privacy
Everything is checked in your browser. Nothing you paste is uploaded or stored; an ABN Lookup link sends a number to the Australian Business Register only when you click it.
Frequently asked questions
How do I check if an ABN is valid?
Paste it above. The checker subtracts 1 from the first digit, multiplies the 11 digits by the ABR’s weights 10, 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19, adds the products and divides by 89: no remainder means the ABN is valid. Then open it on ABN Lookup to see whether it is active and whose it is.
How can I see if a business is registered for GST?
Open its ABN on ABN Lookup — the checker links straight to it for every valid ABN. The page has a “Goods & Services Tax (GST)” line with the business’s GST registration status.
What is the difference between an ABN and an ACN?
An ACN is the 9-digit number ASIC gives a company when it is registered. An ABN is an 11-digit number that identifies any type of business, including sole traders and partnerships as well as companies. Most companies have both, and a company’s ABN is often its ACN with two check digits in front.
Can I check a Tax File Number here?
No. A TFN is confidential, and this page does not check TFNs. Keep yours private: organisations may ask for it only for purposes allowed by tax, personal assistance or superannuation law, and you do not commit an offence by declining to quote it.
Why does an ABN copied from an invoice fail?
Usually a typo: a missing or extra digit, two digits swapped, or the letter O or l typed for 0 or 1 — the result says which. It may also be a different number, such as an ACN or a phone number. Ask the business for its ABN, or search ABN Lookup by its name.
Is it safe to paste a list of supplier ABNs?
Yes. ABNs are public on ABN Lookup, and the check runs in your browser: nothing is uploaded or stored. A number is sent to the Australian Business Register only if you click its ABN Lookup link.