How to Generate a Test ACN for Software Testing

If you're testing a company-registration or supplier form in Australia, you'll need an ACN — the Australian Company Number — and the right value for testing is one that passes the official check without belonging to a registered company. Here's how the ACN checksum works and how to generate valid dummy ones.

The ACN check digit

An ACN is 9 digits. The last digit is a check digit computed from the first eight using a weighted mod-10 scheme:

1. Multiply the first 8 digits by the weights 8, 7, 6, 5, 4, 3, 2, 1.
2. Sum the products.
3. The check digit is (10 − (sum mod 10)) mod 10.

So the 9th digit is fully determined by the first eight — it's not free, and a number whose last digit doesn't match is invalid. This is the check your validation should be enforcing, and the reason a random 9-digit string fails it about nine times out of ten.

ACN vs. ABN — don't confuse them

Companies have both an ACN (9 digits, issued by ASIC) and usually an ABN (11 digits, used for tax). In fact an ABN for a company is typically derived from its ACN. For testing, treat them as separate fields with separate checksums — generate each with the right algorithm rather than trying to convert one into the other by hand.

Generating a valid test ACN

A generator fixes the first eight digits and computes the ninth so the mod-10 check passes by construction. The result is a correctly-formed ACN that no company is registered under — ideal for form validation, QA fixtures, demos, and dev databases.

Valid format is not registration

Passing the checksum means the number is well-formed, not that it's a real registered company. Confirming an ACN belongs to an actual entity is a lookup against ASIC's register — a separate, live concern from format validation. Keep generated ACNs in your test environment; never present one as a real company registration.

Try it

The Australian ACN Generator & Validator generates valid-format test ACNs and validates any ACN against the official weighted checksum, entirely in your browser with nothing sent to a server. For the company's tax number, see the ABN generator; for related testing, there's the TFN generator.