Australia VAT number: format and validation

By Remco from Avatcado

Format

AU followed by 11 digits (the ABN). The local term is Australian Business Number (ABN, English).

Pattern: /^\d{11}$/

  • Australia levies GST (goods and services tax), not VAT; the ABN is the identifier used for it
  • Holding an ABN does not imply GST registration; ABN Lookup shows a separate GST registration date

Example of a registered number: 51 824 753 556

Check digit

Australia VAT numbers carry a check digit (MOD 89): Subtract 1 from the first digit, multiply the 11 digits by the weights 10,1,3,5,7,9,11,13,15,17,19, and the ABN is valid if the sum is divisible by 89.

Check a Australia VAT number

Checks route through ABR (Australian Business Register). Caching is enabled by default. Read the source, original result time and freshness label alongside validity; a cached or stale result does not freshly confirm current registration.

Enter a VAT number to see its registration result, source and freshness

Validate via API

The same validation as an API call, with the example number above:

curl "https://api.avatcado.com/v1/validate?vat_number=AU51824753556" \
  -H "Authorization: Bearer avat_live_your_api_key"
import Avatcado from "@avatcado/node";

const avatcado = new Avatcado("avat_live_your_api_key");
const { data, error } = await avatcado.vat.validate({
  vatNumber: "AU51824753556",
});

if (data?.data.valid) {
  console.log(`Registered: ${data.data.company?.name}`);
}

Free tier includes 500 validations per month. Get an API key or read the API documentation.

How Avatcado validates Australia numbers

  • Primary source: ABR (Australian Business Register).
  • Company name and address: yes.
  • When ABR (Australian Business Register) is down: the most recent cached result, then a refunded 503.

See the full coverage table.

Frequently asked questions

Is an ABN the same as being GST-registered?

No: every Australian business needs an ABN, but GST registration is a separate step required from AUD 75,000 annual turnover (AUD 150,000 for not-for-profits). An ABN can be active with no GST registration.

How do I check whether an ABN is GST-registered?

Look it up on ABN Lookup (abr.business.gov.au): the entry shows the ABN status and the date GST registration started, or omits the GST line entirely if the business is not registered.

How does Avatcado validate Australia numbers and what happens when ABR (Australian Business Register) is down?

Avatcado does not validate Australia numbers through VIES: uncached checks use ABR (Australian Business Register). Caching is enabled by default without a requester VAT number, so a result may reflect an earlier lookup. Read its source, original result time and freshness label alongside validity. A confirmed answer includes the registered company name and address, and there is no separate national fallback register behind ABR (Australian Business Register) for Avatcado to consult if it is unavailable. When ABR (Australian Business Register) cannot answer because of an outage or timeout, an eligible stored result can be served with meta.cached: true and meta.source_status: "unavailable", plus meta.stale: true when it is past the cache window. Requester checks disable stored responses by default; cache=true opts back in. If no eligible stored result can answer, the request returns a refunded 503. Retain the original result time and resolve unavailable checks separately from invalid registrations.

Related guides

VAT rate in Australia

The standard VAT rate in Australia is 10%. See all Australia VAT rates.

Sources