Validate a Polish identifier (NIP tax id, PESEL national id, REGON business registry id, KRS National Court Register number, or IBAN/NRB bank account) and return whether it is valid plus its normalized form. Purely local checksum validation — makes no network calls.

Look up a Polish contractor by NIP on the Ministry of Finance VAT whitelist ("Biała lista podatników VAT") to get their VAT registration status, legal name, REGON/KRS, and registered bank account numbers. Use this to verify a business partner before paying an invoice.

Validate an EU VAT number via VIES (VAT Information Exchange System), the European Commission service that confirms whether a VAT number is currently registered, returning the company name/address when the member state provides them.

Get the official NBP (Narodowy Bank Polski) mid exchange rate for a currency against PLN, either for today or a specific date.

Convert an amount between two currencies using official NBP mid exchange rates (via PLN as the intermediary), either for today or a specific date.