npwp-formatter

Lightweight, zero-dependency formatter & validator for Indonesian NPWP (Nomor Pokok Wajib Pajak / tax ID).

• 🪶 Tiny & zero-dependency — pure TypeScript, framework-agnostic. Works in Node, the browser, React, Next.js (client & server), React Native, etc.
• 🔢 Handles both the legacy 15-digit format (XX.XXX.XXX.X-XXX.XXX) and the current 16-digit / NIK format.
• ✅ Structural validation plus optional Luhn checksum.
• ⛓️ Two APIs: standalone tree-shakeable functions and chainable wrapper.
• 📦 Ships ESM + CJS + .d.ts.

Install

npm install npwp-formatter

Quick start

import { npwp, formatNpwp, isValidNpwp } from 'npwp-formatter';

// Functional API
formatNpwp('091234567890000');               // '09.123.456.7-890.000'
isValidNpwp('09.123.456.7-890.000');         // true
isValidNpwp('091234567890000', { checksum: true });

// Chainable
npwp('091234567890000').format();            // '09.123.456.7-890.000'
npwp('09.123.456.7-890.000').raw();          // '091234567890000'
npwp('091234567890000').type();              // 'pribadi'
npwp('091234567890000').to16().format();     // '0091234567890000'
`${npwp('091234567890000')}`;                // '09.123.456.7-890.000'

Format rules

| Length | Output | Notes | | ------ | ------------------------------ | ------------------------------------------------ | | 15 | XX.XXX.XXX.X-XXX.XXX | Legacy dotted display format. | | 16 | plain digits (no punctuation) | Official 16-digit / NIK format carries no marks. | | other | cleaned digits, unchanged | Input is normalised but not grouped. |

15 vs 16 digit: Since 1 July 2024 NPWP uses 16 digits. For resident individuals it equals the 16-digit NIK; for entities / non-resident individuals it is the old 15-digit NPWP with a leading 0. The dotted format only applies to the 15-digit form.

API

Functions

| Function | Description | | --- | --- | | cleanNpwp(value) | Strip everything but digits. Nullish-safe (''). | | formatNpwp(value) | Display form (see table above). | | isValidNpwp(value, { checksum? }) | Structural validity; checksum: true adds Luhn. | | luhnIsValid(digits) | Raw Luhn (mod-10) check over a digit string. | | getNpwpType(value) | 'pribadi' \| 'badan' \| 'unknown'. | | to16(value) | 15-digit → 16-digit (prepend 0). | | to15(value) | 16-digit corporate form → 15-digit (strip leading 0). |

Constants: NPWP_15_LENGTH, NPWP_16_LENGTH.

npwp(value) → Npwp

| Member | Returns | Description | | --- | --- | --- | | .raw() / .digits | string | Normalised digits. | | .length | number | Digit count. | | .format() / .toString() | string | Display form. | | .isValid(options?) | boolean | Structural (+ optional Luhn). | | .type() | NpwpType | Taxpayer type. | | .to16() / .to15() | Npwp | New instance (immutable). |

Types

type NpwpType = 'pribadi' | 'badan' | 'unknown';
interface IsValidOptions { checksum?: boolean }

License

MIT