International · Validation
New Zealand IRD number validator.
Check a New Zealand IRD number against the real modulus-11 check-digit algorithm Inland Revenue's own specification defines — primary weights first, with a documented secondary-weight fallback for the one case the primary formula can't resolve.
How it works: pad to 8 digits, multiply by the primary weights (3, 2, 7, 6, 5, 4, 3, 2), sum, negate, and take mod 11. If that lands on 10 — not a usable digit — redo the same sum with the secondary weights (7, 4, 3, 2, 5, 2, 7, 6) instead.
Inputs
Result
Enter an IRD number and press Check.
How the IRD number check digit works
New Zealand's Inland Revenue Department (Te Tari Tāke) number identifies individuals and businesses for tax purposes. It's 8 or 9 digits, and unlike Canada's CRA Business Number, it carries a real, published check digit — so a typo can be caught mathematically, not just by shape.
| Step | What happens |
|---|---|
| 1 | Pad the number (minus its final check digit) to 8 digits with leading zeros |
| 2 | Multiply each digit by its primary weight: 3, 2, 7, 6, 5, 4, 3, 2 |
| 3 | Sum the products, negate the sum, and take the result mod 11 |
| 4 | If that result is 10 — not a usable single digit — redo steps 2–3 with the secondary weights instead: 7, 4, 3, 2, 5, 2, 7, 6 |
| 5 | The resulting digit must match the number's actual last digit |
Two of Inland Revenue's own worked examples confirm this tool's arithmetic: 4909185-0 (payload 4909185, primary weights give check digit 0) and NZ 49-098-576 (payload 4909857, primary weights give check digit 6) both check out exactly as Inland Revenue states. A valid IRD number also has to fall between 10,000,001 and 149,999,999 — anything outside that range is rejected before the checksum even runs.
Checksum check only — not an Inland Revenue lookup
A passing checksum confirms the digits are internally consistent with Inland Revenue's own formula — it does not confirm the number was ever actually issued to a real person or entity. IRD numbers aren't publicly searchable the way a business register is; only Inland Revenue itself, or the person/entity it belongs to, can confirm that.
Checksum only — not an Inland Revenue lookup
This tool checks the modulus-11 checksum entirely in your browser. It does not query Inland Revenue, and a checksum-valid result is not proof the number was ever issued. Nothing you type is transmitted, stored, or logged.