NRB

NRB (Numer Rachunku Bankowego) is Poland’s 26-digit domestic bank account number, verified using the MOD-97 checksum from the IBAN standard. An NRB is structurally the numeric portion of a Polish IBAN (i.e. the IBAN without the PL prefix).

Usage

import { Numerik } from '@slashlab/numerik-js'

// Boolean
Numerik.nrb().isValid('61102010260000000000000000')   // true

// Spaced format is accepted
Numerik.nrb().isValid('61 1020 1026 0000 0000 0000 0000')   // true

// IBAN-prefixed format is also accepted
Numerik.nrb().isValid('PL61102010260000000000000000')   // true

// Rich result
const result = Numerik.nrb().validate('61102010260000000000000000')
result.isValid   // true

// Parse to value object
const nrb = Numerik.nrb().parse('61102010260000000000000000')

// Null on failure instead of exception
const maybe = Numerik.nrb().tryParse('bad-input') // null

Value object API

parse() and tryParse() return an Nrb instance.

Core

Method	Return type	Description
getRaw()	string	The original input, untouched.
getNormalized()	string	26 raw digits (prefix and spaces stripped).
toString()	string	Alias for getNormalized().

Formatting

Method	Return type	Description
getFormatted()	string	Human-readable form: CC NNNN NNNN NNNN NNNN NNNN NNNN.
getIban()	string	Full Polish IBAN: PL + 26 digits.
getFormattedIban()	string	Human-readable IBAN: PLCC NNNN NNNN NNNN NNNN NNNN NNNN.

Structure

Method	Return type	Description
getCheckDigits()	string	First 2 digits — MOD-97 check digits.
getSortCode()	string	Digits 2–9 (8 digits) — bank sort code.
getBankCode()	string	Digits 2–4 (3 digits) — bank identifier.
getAccountNumber()	string	Digits 10–25 (16 digits) — customer account number.

Examples

const nrb = Numerik.nrb().parse('61102010260000000000000000')

nrb.getRaw()              // '61102010260000000000000000'
nrb.getNormalized()       // '61102010260000000000000000'
nrb.getFormatted()        // '61 1020 1026 0000 0000 0000 0000'
nrb.getIban()             // 'PL61102010260000000000000000'
nrb.getFormattedIban()    // 'PL61 1020 1026 0000 0000 0000 0000'
nrb.getCheckDigits()      // '61'
nrb.getSortCode()         // '10201026'
nrb.getBankCode()         // '102'
nrb.getAccountNumber()    // '0000000000000000'

Failure reasons

Reason	Value	When
InvalidLength	invalid_length	Input is not exactly 26 digits after normalisation.
InvalidCharacters	invalid_characters	Characters other than digits, spaces, and an optional PL prefix are present.
InvalidChecksum	invalid_checksum	MOD-97 check digit does not match.

Validation algorithm

Uses the MOD-97 algorithm from ISO 13616 (IBAN standard):

1. Reject inputs longer than 40 characters. Strip spaces and hyphens, and an optional PL prefix.
2. Assert exactly 26 digits remain.
3. Rearrange: move the first 2 digits (the check digits) to the end and insert the numeric country code for Poland (2521) between the remaining 24 digits and them, giving a 30-digit string.
4. Compute the 30-digit string modulo 97. The result must equal 1.