How is a New Zealand IRD number validated?

The number is 8 or 9 digits with a check digit at the end. The base (without the check digit) is left-padded to 8 digits and must fall between 10,000,000 and 150,000,000. The 8 base digits are multiplied by primary weights 3,2,7,6,5,4,3,2 and summed; the check digit is 11 minus (sum mod 11), or 0 if that remainder is 0. If the result is 10, the calculation is repeated with secondary weights 7,4,3,2,5,2,7,6; if it is still 10 the number is invalid.

Does a valid check digit mean the IRD number is registered?

No. The check digit only confirms the number is mathematically well-formed and in the valid range. It cannot tell you whether the IRD number was actually issued or who holds it, and this tool never contacts Inland Revenue.

Is my IRD number sent anywhere?

No. The validator is privacy-first. The check digit calculation runs locally in your browser with JavaScript — there are no network requests and your IRD number never leaves your device.

New Zealand IRD Number Validator — Check Digit Verification

New Zealand IRD number validator

Validate a New Zealand IRD number using Inland Revenue’s published weighted modulus-11 check digit algorithm. The last digit is a check digit: the base is left-padded to 8 digits, must sit between 10,000,000 and 150,000,000, and is run through primary weights 3,2,7,6,5,4,3,2 — falling back to secondary weights 7,4,3,2,5,2,7,6 when the first pass produces a check digit of 10.

The breakdown shows whether the base is in range and how the expected and supplied check digits compare, so you can see exactly why a number passes or fails.

Privacy-first: every calculation runs in your browser. Nothing is uploaded, stored or sent to any server, and this tool does not query Inland Revenue or any other database.