nz-bank-account-validator

A validator for New Zealand bank accounts

Installation

npm install --save @fnzc/nz-bank-account-validator

or

yarn add @fnzc/nz-bank-account-validator

Usage

Function requires four string parameters:

• Bank ID
• Bank Branch
• Account Base
• Suffix Returns a boolean.

var bankAccountValidator = require('@fnzc/nz-bank-account-validator');
bankAccountValidator.isValidNZBankNumber('00', '0000', '00000000', '000');

Algorithm

The algorithm is based on the 'Non-Resident Withholding Tax And Resident Withholding Tax Specification Document' issues by the Inland Revenue on the 31st of March 2016.

Bank account number validation

The bank account number format used by all banks is numeric and includes the following parts:

• Bank ID (maximum 2 digits)
• Bank branch (maximum 4 digits)
• Account base number (maximum 8 digits)
• Account suffix (maximum 4 digits).

For processing at Inland Revenue the fields for the individual account number parts are all of maximum size. If less than the maximum number of digits is supplied, then values are right justified and the fields padded with zeroes (where applicable).

The first step in the validation process is to verify the bank branch number. For every bank ID, a range of branch numbers is allocated. If the bank ID is not one of those listed below or the branch number is not included in the range(s) specified, the bank account number is invalid. If the branch number is valid, then derive the appropriate code from the “Algorithm” column below and perform the second validation step as outlined in the first paragraph over the page.

Bank ID	Valid Branch Numbers	Algorithm
01	0001 - 0999, 1100 - 1199, 1800 - 1899	See note
02	0001 - 0999, 1200 - 1299	See note
03	0001 - 0999, 1300 - 1399, 1500 - 1599, 1700 – 1799 , 1900 - 1999	See note
04	2020 - 2024
06	0001 - 0999, 1400 - 1499	See note
08	6500 - 6599	D
09	0000	E
10	5165 - 5169	See note
11	5000 - 6499, 6600 - 8999	See note
12	3000 - 3299, 3400 – 3499, 3600 - 3699	See note
13	4900 - 4999	See note
14	4700 - 4799	See note
15	3900 - 3999	See note
16	4400 - 4499	See note
17	3300 - 3399	See note
18	3500 - 3599	See note
19	4600 - 4649	See note
20	4100 - 4199	See note
21	4800 - 4899	See note
22	4000 - 4049	See note
23	3700 - 3799	See note
24	4300 - 4349	See note
25	2500 - 2599	F
26	2600 - 2699	G
27	3800 - 3849	See note
28	2100 - 2149	G
29	2150 - 2299	G
30	2900 - 2949	See note
31	2800 - 2849	X
33	6700 - 6799	F
35	2400 - 2499	See note
38	9000 - 9499	See note
88	8800 - 8805

Note: If the account base number is below 00990000 then apply algorithm A, otherwise apply algorithm B.

The second validation step is a modulus n algorithm applied to the whole account number. The algorithm type is derived from the table on the previous page. Follow this process:

• Identify the corresponding weight factor for every digit in the account number as showninthetablebelow. Note:allfields(iebankID,bankbranch,accountbase and account suffix) are right justified and padded with zeroes.
• Add together the products of the weight factors and their associated account number digit. If the algorithm E or G is used then add the two digits of the product (tens and ones), and again the two digits of the result before summing (see example 3 on page 16).
• Divide the sum by the value in the “Modulo” column below. If the remainder is zero then the bank account number is valid.

Algorithm	Bank	Branch	Account Base	Suffix	Modulo
A	00	6379	00A58421	0000	11
B	00	0000	00A58421	0000	11
C	37	0000	91A53421	0000	11
D	00	0000	07654321	0000	11
E	00	0000	00005432	0001	11
F	00	0000	01731731	0000	10
G	00	0000	01371371	0371	10
X	00	0000	00000000	0000	1

Note 1: Algorithm C is not currently used by the banks. Note 2: Algorithm X (for Bank ID 31) always verifies the bank account number to be valid. It is included in this table so the same validation logic can be applied to all account numbers.

Changelog

Contributing

Pull requests are welcome.

License