ABN and ACN validator

Paste ABNs or ACNs — one or hundreds — and see which ones pass the official check-digit rules before they reach an invoice.

AustraliaFree, no sign-up

Before you use it

Works well for

  • Catching typos in ABNs and ACNs
  • Checking supplier lists before payment runs
  • Seeing whether an ABN contains a valid ACN

Not the right tool for

  • Confirming the business is active or registered for GST — use ABN Lookup
  • New Zealand NZBNs or other countries' numbers

How the ABN check works

An ABN has 11 digits. Subtract 1 from the first digit, multiply each digit by the weights 10, 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19, and add them up. A valid ABN gives a total divisible by 89.

ABN vs. ACN

The ACN is the 9-digit number ASIC gives to companies. A company's ABN is usually its ACN with two extra digits in front, so the tool also tells you when an ABN contains a valid ACN.

Before you pay an invoice

A valid ABN only means it's typed correctly. Check the business name and GST registration on the government's ABN Lookup — if a supplier doesn't quote an ABN, you may need to withhold tax from the payment.

Frequently asked questions

Does this confirm GST registration?

No. ABN Lookup shows whether a business is registered for GST and since when.

Can I format ABNs with spaces?

Yes — spaces are ignored, and valid numbers are shown in the standard 11 222 333 444 format.

Is anything sent to a server?

No. The check runs entirely in your browser.