polish-company-utils

Zero-dependency validators and helpers for Polish business identifiers — NIP, REGON, PESEL, bank account (NRB/IBAN) and the tax micro-account (mikrorachunek podatkowy).

• Zero dependencies, tiny, no build step.
• Works with both require and import, ships TypeScript types.
• Same checksum algorithms that run in production on skanfirmy.pl — free tools to verify Polish companies by NIP / KRS / REGON.

Install

npm install polish-company-utils

Usage

// CommonJS
const { isValidNip, isValidRegon, generateTaxMicroAccount } = require("polish-company-utils");
// …or ESM: import { isValidNip } from "polish-company-utils";

isValidNip("525-234-40-78");   // true  (separators are stripped)
isValidNip("1234567890");      // false (bad checksum)

isValidRegon("000331501");     // true  (9- or 14-digit)
isValidPesel("44051401359");   // true

// Individual tax micro-account (PIT/CIT/VAT) from a NIP or PESEL:
generateTaxMicroAccount("7393933151");
// → { nrb: "…26 digits…", iban: "PL…", type: "NIP" }

API

| Function | Returns | Notes | |---|---|---| | isValidNip(nip) | boolean | 10-digit tax ID checksum. Accepts strings/numbers, strips separators. | | formatNip(nip) | string | 123-456-32-18. | | isValidRegon(regon) | boolean | 9- or 14-digit statistical number. | | isValidPesel(pesel) | boolean | 11-digit personal number checksum. | | peselInfo(pesel) | { date, year, month, day, sex } \| null | Date of birth + sex encoded in a PESEL. | | isValidNrb(nrb) | boolean | 26-digit Polish bank account (ISO 7064 mod-97-10). Optional PL prefix. | | isValidIban(iban) | boolean | Any IBAN (ISO 13616). | | formatNrb(nrb) | string | Grouped 61 1090 1014 …. | | generateTaxMicroAccount(id) | { nrb, iban, type } | Mikrorachunek for a valid NIP/PESEL. Throws on invalid input. |

All functions are pure and synchronous. Validation functions never throw — they return false for malformed input; only generateTaxMicroAccount throws (on an invalid identifier), because there is no meaningful account to return.

Need the data, not just the maths?

This package validates and generates locally. To actually look up a company — VAT status, KRS data, official REGON name and address — use the free hosted tools and API:

• skanfirmy.pl — verify a Polish company by NIP/KRS/REGON in the browser.
• skanfirmy.pl/mcp — an MCP server so AI agents can call the same lookups directly. Plain REST too: skanfirmy.pl/nip/{nip}, /regon/{nip}, /vies/{country}/{number}.
• otwarteapi.pl — a catalog of official Polish & EU public APIs for agents.

Contributing

Issues and PRs welcome. Run the tests with:

npm test

Author

Bartosz Kuć · skanfirmy.pl · github.com/bartosz-kuc · linkedin.com/in/bartosz-kuc

License

MIT © Bartosz Kuć