Tax.IrdValidator 1.0.4

IrdNumberValidator

.Net Library to validate New Zealand IrdNumber (Tax Number)

How to use

To use Tax.IrdValidator , add it by searching on Nuget manager or use the install command below

Install-Package Tax.IrdValidator

Usage

var irdNumber = "111111111"; //111-111-111 also valid
irdNumber.IsIrdNumberValid(); //returns true
irdNumber.IsIrdNumberValid(10000000,150000000,"32765432","74325276"); //returns true 
//The parameters are optional, useful when Ird changes them

IR number validation - modulus 11 digit check

The IRD number format used by Inland Revenue is an eight or nine digit number consisting of the following parts - • A seven or eight digit base number • A trailing check digit Check digit validation The following steps are to be performed -

1. Check the valid range • If the IRD number is < 10-000-000 or > 150-000-000 then the number is invalid. This step ensures that the IRD number is in the already issued range, or is in the range expected to be issued in the next 10 years.
2. Form the eight digit base number: • Remove the trailing check digit. • If the resulting number is seven digits long, pad to eight digits by adding a leading zero.
3. Calculate the check digit: • To each of the base number’s eight digits a weight factor is assigned. From left to right these are: 3, 2, 7, 6, 5, 4, 3, 2. • Sum together the products of the weight factors and their associated digits. • Divide the sum by 11. If the remainder is 0 then the calculated check digit is 0. • If the remainder is not 0 then subtract the remainder from 11, giving the calculated check digit. • If the calculated check digit is in the range 0 to 9, go to step 5. • If the calculated check digit is 10, continue with step 4.
4. Re-calculate the check digit: • To each of the base number’s eight digits a secondary weight factor is assigned. From left to right these are: 7, 4, 3, 2, 5, 2, 7, 6. • Sum together the products of the weight factors and their associated digits. • Divide the sum by 11. If the remainder is 0 then the calculated check digit is 0. • If the remainder is not 0 then subtract the remainder from 11, giving the 00 calculated check digit. • If the calculated check digit is 10, the IRD number is invalid.
5. Compare the check digit: • Compare the calculated check digit to the last digit of the original IRD number. If they match, the IRD number is valid.

Reference: https://www.classic.ird.govt.nz/resources/d/a/dac415c0-456f-4b2f-87b6-0e76cbedd3ec/2020+RWT%26NRWT+Specification+Document+v1.0.pdf