How do I check whether a NIP belongs to an active company?

Use the official registers, not a checksum. The Ministry of Finance’s list of VAT taxpayers, known as the white list, shows whether a NIP is an active VAT payer, and CEIDG or KRS show whether the business itself is registered. For a PL-prefixed number on an EU invoice, the European Commission’s VIES service confirms the VAT registration. This tool only tells you whether the number is well formed.

Why does my NIP fail validation?

Most often a digit was mistyped: the tenth digit must equal the weighted sum of the first nine modulo 11. Make sure you entered ten digits; dashes, spaces and a leading PL are ignored. If the tool says the weighted sum leaves 10, that prefix can never form a valid NIP, so the number was copied wrong somewhere.

Do private individuals need a NIP in Poland?

Usually not. Since 2012 people who do not run a business and are not registered for VAT use their PESEL as their tax identifier. A NIP is issued to companies, organisations and individuals who run a business or are VAT-registered, and that is the number that appears on their invoices.

NIP Validator – Check a Polish Tax Number (NIP)

Numer Identyfikacji Podatkowej

Poland · Individuals and companies

000-000-00-00

Enter a number to check

Paste or type the number — punctuation is optional.

Other identifiers

Cross-border

IBAN LEI EU VAT

Americas

CPF CNPJ CUIT / CUIL RUT / RUN NIT RUC CURP SIN / NAS SSN EIN

Oceania

ABN ACN TFN IRD number

Africa

SA ID KRA PIN الرقم القومي NIN

What this check does — and what it cannot do

This tool checks the number's structure and its check digit, using the published algorithm for that document. A number that passes is well formed: it is arithmetically consistent and could have been issued.

It cannot tell you whether the number was actually issued, whether it is active, or who it belongs to. Only the issuing tax authority can confirm that, through its own lookup service. Treat a passing result as "worth submitting", never as proof of identity.

The generator produces numbers that satisfy the same checksum, for filling forms while developing and testing software. They are arithmetic, not records: they are not drawn from any register and do not correspond to a real holder. No generator is offered for the US Social Security Number.

Calculated in your browser. Nothing you enter is sent anywhere.

One in every eleven nine-digit prefixes can never become a valid NIP

The check digit is the weighted sum modulo 11. When that remainder comes out as 10 there is no single digit that can express it, so the whole prefix is unusable — no tenth digit completes it. Sampling the space shows this happens to 9.09% of prefixes, almost exactly one in eleven, which is why NIP numbers are not simply issued in sequence.

How it works

Applies the official weights to the first nine digits and compares the remainder with the tenth.
Rejects prefixes whose remainder is 10, which no valid NIP can have.
Shows the EU VAT form, which is the same ten digits behind the PL prefix.

weights 6 5 7 2 3 4 5 6 7 applied to digits 1-9
remainder = sum mod 11
if remainder = 10 → this prefix has no valid NIP
otherwise the tenth digit must equal the remainder

Worked example

Why a tenth digit sometimes cannot exist.

the weighted sum of the first nine digits is taken modulo 11
a remainder of 0 to 9 is written directly as the check digit
a remainder of 10 would need two characters in a one-character field
such prefixes are simply never issued
measured across the space, 9.09% of prefixes fall into that hole

A ten-digit number where the last digit is fully determined by the first nine — except for the one prefix in eleven where it cannot be determined at all.

Reading the result

Modulo 11 is chosen because 11 is prime, which makes the checksum catch every single-digit error and every transposition of two digits. The price is the unusable remainder of 10, and different schemes pay it differently: some map 10 to zero, Poland's NIP simply does not issue the prefix.
A valid NIP is not a trading NIP. The number can be well formed, correctly issued and still belong to a business that is deregistered or not VAT-registered. For anything that matters commercially, check the number against the official register rather than against arithmetic.
The EU VAT form is just PL followed by the same ten digits, with no separate check. If a counterparty gives you a PL VAT number, validating it here validates the NIP inside it.
A generator is offered because filling a test system with well-formed company numbers is ordinary work. The numbers it emits satisfy the checksum and are not drawn from any register of real taxpayers.

Common questions

How do I check whether a NIP belongs to an active company?: Use the official registers, not a checksum. The Ministry of Finance’s list of VAT taxpayers, known as the white list, shows whether a NIP is an active VAT payer, and CEIDG or KRS show whether the business itself is registered. For a PL-prefixed number on an EU invoice, the European Commission’s VIES service confirms the VAT registration. This tool only tells you whether the number is well formed.
Why does my NIP fail validation?: Most often a digit was mistyped: the tenth digit must equal the weighted sum of the first nine modulo 11. Make sure you entered ten digits; dashes, spaces and a leading PL are ignored. If the tool says the weighted sum leaves 10, that prefix can never form a valid NIP, so the number was copied wrong somewhere.
Do private individuals need a NIP in Poland?: Usually not. Since 2012 people who do not run a business and are not registered for VAT use their PESEL as their tax identifier. A NIP is issued to companies, organisations and individuals who run a business or are VAT-registered, and that is the number that appears on their invoices.