Data and files
Number validators — NIP, REGON, KRS, PESEL, IBAN, EAN, EU VAT, land register and VIN
Most identifiers used in Polish business have a built-in check digit, so a typo can be caught without querying any register. We put the nine most common ones in a single tool - switch a tab, paste a number, and you immediately see not just the verdict but the reason a number was rejected.
Free · no signup · runs in your browser
You can paste it with dashes and a PL prefix.
Need to clean up a whole database?
The same algorithm can run across thousands of records at once. It is the usual first step before a KSeF integration or a migration to a new system. A human replies within 24 hours.
Get in touchHow it works
- 01
Pick the identifier type
NIP, REGON, KRS, PESEL, IBAN, EAN/GTIN, EU VAT, land register number or VIN. Each has its own algorithm and its own traps.
- 02
Paste the number in any format
Dashes, spaces, country prefixes and lower case are stripped or normalised automatically.
- 03
Read the verdict with reasoning
Not just "valid" or "invalid", but the expected check digit, the detected number type and data decoded from its structure.
Assumptions and limits
- A correct checksum only means the number is well-formed. It does not confirm that the entity exists, is a registered VAT payer, or that an account belongs to the person who gave it to you.
- REGON comes in two lengths (9 and 14 digits) and each uses different weights - tools supporting only the shorter variant falsely reject local unit numbers.
- PESEL encodes the century in the month: for people born after 1999, 20 is added to the month. It is the most common cause of misread dates of birth.
- KRS has no check digit - offline you can only verify the format and restore stripped leading zeros.
- The VIN check digit is mandatory only in the North American market, so a factory-correct European VIN can come out as invalid.
- A PESEL is personal data under GDPR. That is why everything runs locally - no number is sent, logged or stored. You can disconnect from the internet and the tool still works.
Frequently asked questions
Does the validator check whether a company really exists? +
No. Only the mathematical correctness of the number is checked. To verify an entity exists and its VAT status, use the Ministry of Finance VAT register, and the KRS search for registration data.
Why do you not check the number against the VAT white list? +
Because the VAT register API has daily request limits that make it impossible to offer as a free browser service for everyone. Rather than shipping a tool that stops working by mid-afternoon, we say plainly where to check.
Do the numbers I enter go anywhere? +
No. All validation happens in your browser. Nothing is sent to a server, reaches any log or is stored - that includes PESEL numbers.
I have a whole database to check, not single numbers +
That is what our counterparty data quality audit is for: upload a CSV and get a report across all records at once, including duplicates and gaps. Same engine, different scale.
Which identifier causes the most trouble in databases? +
By far the ones with leading zeros: KRS, land register numbers and EAN codes. Excel treats them as numeric and strips the zeros on import, after which the records no longer match the registers.
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