IRD Validator
Check whether a New Zealand IRD number is valid
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How an IRD number is checked
Inland Revenue publishes the algorithm, which is unusual and welcome. Drop the final digit, pad what is left to eight digits with a leading zero, multiply by the weights 3, 2, 7, 6, 5, 4, 3 and 2, and take the total modulo 11. Subtracting that remainder from 11 gives the check digit. When the answer comes out as 10 there is no single digit that works, so a second weighting (7, 4, 3, 2, 5, 2, 7, 6) is tried; if that also gives 10, the number is not a valid IRD number at all. This tool applies both passes, which is the step lightweight implementations tend to skip.
The range changed in February 2026
A valid IRD number must sit between 10,000,000 and 200,000,000. That ceiling used to be 150,000,000; Inland Revenue raised it on 10 February 2026 and the length of the number did not change. Anything above the old limit is genuinely valid, but plenty of software has not been updated, so this tool flags such numbers with a warning rather than quietly passing them. If you are auditing a system, those are exactly the numbers to test with.
Eight digits and nine digits are the same number
49-091-850 and 049-091-850 are one number written two ways, and both validate here. Store IRD numbers as digits without punctuation, keep the leading zero if you store them as text, and never store one in an integer column that will strip it. The check digit itself is the last digit, not the first.
What a pass does not mean
The arithmetic says a number is well formed. It says nothing about whether Inland Revenue has issued it, who holds it, or whether it is active, and there is no public service that will tell you. For test data that is safe to paste into a form, use the IRD generator instead of a real number. Everything on this page runs in your browser and nothing you type is transmitted.
Frequently Asked Questions
What is the valid range for an IRD number?
From 10,000,000 to 200,000,000. The upper limit was 150,000,000 until Inland Revenue raised it on 10 February 2026; the length of the number did not change. Numbers above the old ceiling are valid but will be rejected by any system still carrying the previous limit, so this tool flags them rather than passing them silently.
Why do some IRD numbers have eight digits and some nine?
They are the same format. Validation pads the base number to eight digits with a leading zero before applying the weights, so 49-091-850 and 049-091-850 are one number written two ways and both check out. Store IRD numbers as text so the leading zero survives.
What are the secondary weights for?
The primary weights 3, 2, 7, 6, 5, 4, 3, 2 sometimes produce a check digit of 10, which cannot be written in one place. Inland Revenue specifies a second set, 7, 4, 3, 2, 5, 2, 7, 6, to be tried in that case. If the second pass also gives 10 the number is invalid. Implementations that skip the fallback reject a small share of perfectly good numbers.
Does a valid IRD number mean the person or company is registered?
No. The check confirms the digits are internally consistent, nothing more. Inland Revenue does not offer a public service for confirming that a number has been issued or who holds it, so a pass here should be read as "safe to accept into a form", not as verification.