Free NIP Validator
Check whether a NIP (Polish tax ID) is valid - format and checksum - before issuing a KSeF invoice. Online, instant and no registration.
Free, with a shared limit
Without registering, you can use the tools a total of 2 times within 24 hours. This limit is shared across all tools.
- 2 total uses within 24 hours
- After creating an account: access to GUS data and manual editing of every invoice field
- Full access to all platform modules
Free Tools that humans LOVE to use
Share your thoughts - every review helps us make these tools better for you.
“Walidator wyłapał mi błąd w sumie P_15 na czterech fakturach z ERP, zanim je wysłałam do KSeF. Oszczędziłam dzień na korektach.”“Najszybszy sposób na debug FA(3) – wklejam XML, widzę dokładnie który element nie trzyma schematu. Używam codziennie.”“Przed go-live KSeF przepuściliśmy cały hurt faktur testowych. Raport błędów jest czytelny nawet dla nietechnicznych osób w zespole.”“Darmowe, bez rejestracji, działa w przeglądarce. Dokładnie tego potrzebowałem, żeby sprawdzić fakturę od nowego dostawcy.”What is a NIP and how does the checksum work?
A NIP (Polish tax identification number) is a 10-digit number identifying a business. The last digit is a check digit derived from the other nine using the weights 6, 5, 7, 2, 3, 4, 5, 6, 7. The validator verifies the format and this checksum, so you can catch a typo before it ends up on a KSeF invoice.
Type or paste the NIP number → Click Check NIP → See the result: format and checksum
Sign in to KSeFGPT and, in the Counterparties module, pull the company name and address by NIP - straight from the GUS registry.
Free validator vs KSeFGPT account
| Free validator | KSeFGPT account | |
|---|---|---|
| NIP format and checksum verification | Within the usage limit | Depends on the plan |
| Retrieving company details from GUS | No | Depends on the plan |
| Saving counterparties and history | No | Depends on the plan |
| Creating and sending invoices | No | Depends on the plan |
| AI assistant for KSeF | Separate public chat | Depends on the plan |
| Support | Instructions and knowledge base | Depends on the plan |
Frequently asked questions about NIP validation
How does the NIP validator work?
It checks the number's format and check digit. A Polish NIP consists of 10 digits. The tool helps catch typing errors before you use the number on an invoice.
What is the NIP checksum?
The first nine digits are multiplied in order by weights 6, 5, 7, 2, 3, 4, 5, 6, 7. The remainder of the sum divided by 11 is compared with the last digit. A remainder of 10 or a mismatch means the number is invalid.
Does the NIP validator check the VAT whitelist?
No. Checking format and checksum is different from checking taxpayer status or a bank account in the Polish Ministry of Finance's VAT whitelist.
Does the validator confirm that a company exists?
No. The tool checks the number itself without confirming company details in a register. You can retrieve counterparty details from GUS in a KSeFGPT account if your selected plan includes this feature.
Why is a correct NIP important on an invoice?
NIP identifies a party to the transaction. A typing error may hinder document acceptance or associate it with the wrong entity. After checking the number, also compare the company details with those of the counterparty.
Is NIP validation a paid service?
The tool is free within a shared limit of 2 free-tool uses per 24 hours. A KSeFGPT account has separate features and limits defined by its plan.
Bring counterparty details into KSeFGPT
A KSeFGPT account lets you retrieve company details by NIP and use them when creating invoices. Check feature availability in your selected plan.
Create an account