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):

Reject inputs longer than 40 characters. Strip spaces and hyphens, and an optional PL prefix.
Assert exactly 26 digits remain.
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.
Compute the 30-digit string modulo 97. The result must equal 1.