NIP

NIP (Numer Identyfikacji Podatkowej) is Poland’s 10-digit tax identification number, used by both individuals and legal entities.

Usage

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

// Boolean
Numerik.nip().isValid('5260250274')   // true

// Rich result
const result = Numerik.nip().validate('5260250274')
result.isValid   // true

// Parse to value object
const nip = Numerik.nip().parse('5260250274')

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

NIP accepts hyphens and spaces as separators in the input:

Numerik.nip().isValid('526-025-02-74')   // true
Numerik.nip().isValid('526 025 02 74')   // true

Value object API

parse() and tryParse() return a Nip instance.

Core

Method	Return type	Description
getRaw()	string	The original input, untouched.
getNormalized()	string	10 raw digits (hyphens and spaces removed).
toString()	string	Alias for getNormalized().

Formatting & metadata

Method	Return type	Description
getFormatted()	string	Canonical NNN-NNN-NN-NN display form.
getFormattedAlternative()	string	Alternative NNN-NN-NN-NNN display form used by some legal entity documents.
getTaxOfficeCode()	string	First 3 digits — indicates the issuing tax office.

Examples

const nip = Numerik.nip().parse('5260250274')

nip.getRaw()                   // '5260250274'
nip.getNormalized()            // '5260250274'
nip.getFormatted()             // '526-025-02-74'
nip.getFormattedAlternative()  // '526-02-50-274'
nip.getTaxOfficeCode()         // '526'

// With formatted input
const nip2 = Numerik.nip().parse('526-025-02-74')
nip2.getRaw()          // '526-025-02-74'
nip2.getNormalized()   // '5260250274'

Failure reasons

Reason	Value	When
InvalidLength	invalid_length	Input is not exactly 10 digits after stripping separators.
InvalidCharacters	invalid_characters	Characters other than digits, hyphens, and spaces are present.
InvalidFormat	invalid_format	First 3 digits are 000 (no valid tax office has code 000).
InvalidChecksum	invalid_checksum	Checksum digit does not match.
AllSameDigit	all_same_digit	All digits are identical — strict mode only.

Validation algorithm

Weights: 6, 5, 7, 2, 3, 4, 5, 6, 7

1. Strip hyphens and spaces. Assert exactly 10 digits.
2. Assert the first 3 digits are not 000.
3. Multiply each of the first 9 digits by its weight, sum, take mod 11. The result must equal digit 10; since a single digit can only be 0–9, a modulo result of 10 can never match and always fails with InvalidChecksum.
4. In strict mode, reject inputs where all 10 digits are identical; fail with AllSameDigit.

See Algorithms for the full reference.