Polish NIP Validator
ValidatorValidate a Polish NIP (tax identification number) instantly. Confirms the mod-11 check digit and flags the rare case where a 9-digit base has no valid check digit at all. Free, runs in your browser.
Validating an individual instead of a business?
NIP identifies businesses and taxpayers. Poland's national ID number for individuals is the PESEL, which also decodes birth date and sex. Try our PESEL Validator →
About this tool
About Polish NIP Validator
NIP (Numer Identyfikacji Podatkowej) is Poland's 10-digit tax identification number, joining this site's proven 'tax ID' category alongside NIF, CNPJ, SIRET, and TVA. It uses a mod-11 check digit over the first 9 digits with weights 6, 5, 7, 2, 3, 4, 5, 6, 7.
Paste a NIP and the tool recomputes the mod-11 check digit and compares it to the 10th digit. It also specifically detects and labels the case where a 9-digit base has no valid check digit at all (mod-11 result of 10), the same 'no valid check digit exists' pattern this site uses for SEDOL, rather than reporting it as a plain mismatch.
Use this to verify a supplier's or customer's NIP before invoicing, to debug a Polish tax-ID field in your own system, or to understand the mod-11 algorithm behind it.
Instant, fully client-side validation with a genuine, publicly documented checksum, and an honest distinct message for the rare 9-digit bases that can never have a valid NIP.
Key Features
- Verifies the mod-11 check digit
- Distinctly reports the 'no valid check digit exists' case
- 100% browser-based, no data sent
FAQ
Polish NIP Validator — Frequently Asked Questions
How is the NIP check digit calculated?
Multiply the first 9 digits by the fixed weights 6, 5, 7, 2, 3, 4, 5, 6, and 7, sum the results, and take the sum mod 11. The result must equal the 10th digit.
What does "no valid check digit exists" mean?
For roughly 1 in 11 possible 9-digit bases, the mod-11 calculation comes out to exactly 10 — which can't be written as a single check digit. That specific 9-digit prefix simply cannot form a valid NIP, the same kind of edge case this site's SEDOL validator flags rather than reporting as an ordinary mismatch.
Why did my NIP fail even though it's 10 digits?
The format check (10 digits) only confirms the shape. The 10th digit must also match the mod-11 checksum computed from the first 9 — a single mistyped digit anywhere in the number will produce a format-valid but checksum-invalid NIP.
Can this tool confirm a NIP belongs to a real, registered business?
No. This is a mathematical checksum check only. Confirming a NIP is currently registered and active requires access to Poland's tax authority systems, which this site cannot query.
Tips
- Spaces and hyphens are stripped automatically before validation
- A mod-11 result of 10 means no valid NIP can start with those 9 digits
- Use the NIP Generator on this site to create valid test numbers
- PESEL is Poland's separate national ID for individuals, not businesses
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