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GST number checker

This checks a GST number’s format and Inland Revenue’s check digit, in your browser. It can’t tell you whether the business is registered for GST.

8 or 9 digits, like 49-091-850 or 136-410-132

Check

Valid GST number

As printed on an invoice
GST No. 49-091-850
Check digit
Matches

A valid number is well formed, not necessarily registered for GST. Ask your client, or check their invoices, before you rely on it.

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What this checks, and what it can’t

  • Checks: the number has 8 or 9 digits (hyphens and spaces are ignored).
  • Checks: it falls between 10,000,000 and 200,000,000, the range Inland Revenue uses.
  • Checks: the mod 11 check digit Inland Revenue publishes, which catches most typos.
  • Can’t check: whether the number is registered for GST, or to whom.

How the check digit works

Pad an 8-digit number to 9 with a leading 0. Multiply the first eight digits by 3, 2, 7, 6, 5, 4, 3 and 2, add them up and divide by 11. The check digit is 11 minus the remainder (0 when the remainder is 0).

If that gives 10, Inland Revenue uses a second set of weights, 7, 4, 3, 2, 5, 2, 7 and 6. If that gives 10 again, the number isn’t valid.

49-091-850 passes with the first weights; 136-410-132 needs the second.

GST numbers on invoices

  • A tax invoice for more than NZ$200 must show your GST number.
  • Your GST number is usually the same as your IRD number.
  • Without it, a GST-registered client can’t claim the GST back.

Last updated . This calculator is a guide, not tax advice.

Frequently asked questions

Is my GST number the same as my IRD number?

Usually, yes. Most businesses’ GST number is their 8- or 9-digit IRD number, printed like 49-091-850 or 136-410-132.

Does this tell me who a GST number belongs to?

No. It only checks the number’s format and check digit, offline. Ask your client, or check the GST number on their own invoices.

Why do some IRD numbers start with 1?

Inland Revenue has issued 9-digit numbers above 100,000,000 for years, and raised the upper limit to 200,000,000 in 2026.