Australia ABN check
Check that a Australia ABN is well formed and its check digit is right, before you pay or onboard a supplier. Format only
Example: 51 824 753 556 (Australian Taxation Office). No account needed: 10 lookups a day per network, shared with the keyless API.
What this check tells you
Format only
We check the structure and the check digit published by the issuing authority, offline. That catches typos and made-up numbers. It does not show that the business exists, is registered or is active, so a well-formed number gets review, never pass. To confirm registration, use the official lookup: ABN Lookup (Australian Business Register).
Australia ID formats we check
| ID type | Level | Check digit | API endpoint | Official lookup |
|---|---|---|---|---|
| ABN Australian Business Number (ABN) | Format only | ATO weighted mod 89 | GET /v1/au/abn/{id} | ABN Lookup (Australian Business Register) |
| ACN Australian Company Number (ACN) | Format only | ASIC weighted mod 10 | GET /v1/au/acn/{id} | ABN Lookup (Australian Business Register) |
From code
Same key and quota as every other country. A well-formed request costs one lookup; a source that does not answer returns HTTP 503 and is not counted.
curl "https://taxid.halpii.com/v1/au/abn/51%20824%20753%20556" \
-H "Authorization: Bearer $KEY"Get a no-cost API key (100 lookups a day) or read the API docs.
Questions
Does a valid ABN mean the company exists?
No. This is a format check: it confirms the structure and check digit, not that the business exists or is active. Confirm registration with ABN Lookup (Australian Business Register).
Where does the data come from?
No registry is queried. The rules come from the issuing authority's published format and check-digit algorithm (ATO weighted mod 89).
Can I check ABNs from code or in bulk?
Yes. The same check is available over the REST API (GET /v1/au/abn/{id}) and the MCP server, with the same key as every other country. See the API docs.
Is this service affiliated with the Australia tax authority?
No. HALPII Tax ID is an independent service run by HALPII S.A.C. (Lima, Peru). Results are informational, not legal or tax advice.
Other countries in Asia-Pacific
All countries and verification levels
Last updated 2026-11-14. An independent service run by HALPII S.A.C. (Lima, Peru), not affiliated with or endorsed by any Australia authority.