NISS Validator
Paste a NISS (Portuguese social security number) and confirm in seconds whether the check digit is correct. Everything runs in your browser. Nothing is sent anywhere. Looking for your own NISS? Right after the validator I explain where to find it, and why there is no lookup by NIF.
By Elijah4 MINHow to find your NISS number
The quickest places are the back of your Cartão de Cidadão (citizen card) and any payslip: the NISS is on both. With neither to hand, log into Segurança Social Direta with the Cartão de Cidadão or Chave Móvel Digital, two logins that do not ask for the number. A NISS has 11 digits, and the validator above confirms you copied it correctly.
| Where | What you need | When |
|---|---|---|
| Cartão de Cidadão (back of the card) | Just the card. Citizen card holders get the NISS automatically when they apply for the card. | Instant |
| Payslip (recibo de vencimento) | Any payslip from your employer. By law it must show your Segurança Social registration number (Labour Code, art. 276(3)). | Instant |
| Segurança Social Direta, under Perfil > Dados pessoais | Log in with your Cartão de Cidadão and a card reader, or with Chave Móvel Digital (digital mobile key). The username-and-password login already asks for the NISS. | Instant |
| Consultar pedido de NISS, on the Segurança Social portal | If you requested the NISS through the online form: request ID, email and date of birth, plus a biometric check to download the proof (comprovativo). | Instant if the biometric check passes; otherwise by video appointment |
| gov.pt (personal area or the gov.pt app) | If you made the identification-numbers request for foreigners (NIF, NISS and health user number): the same login you used to apply, e.g. Chave Móvel Digital linked to your passport. Also at Espaços Cidadão that offer the service. | Instant |
None of these work? The Linha Segurança Social (helpline) answers on working days, 9:00 to 18:00, on 210 545 400 or 300 502 502, and Siga books an in-person or video appointment.
Can you look up a NISS by NIF?
No public service takes a NIF and returns a NISS. The two numbers come from separate databases, run by Finanças (the tax authority) and Segurança Social, and the Cartão de Cidadão law bans cross-matching them except where the law or the CNPD (data protection authority) allows it (Lei 7/2007, art. 16). For your own NISS, the NIF helps by another route: with your NIF and Portal das Finanças password you can activate Chave Móvel Digital (the temporary PIN arrives by post) and then log into Segurança Social Direta. If you need someone else’s NISS, ask them.
Don’t have a NISS yet? The request, step by step, is in the guide How to get your NISS.
How this works
A NISS has 11 digits and ends in a check digit. That digit comes from the first 10: multiply each by the weights 29, 23, 19, 17, 13, 11, 7, 5, 3 and 2, add the products, take the remainder of dividing by 10, then compute 9 minus that remainder. The first digit gives the holder type: 1 for an individual, 2 for a legal entity. If the result does not match the 11th digit, the number is wrong.
Frequently asked
How is the NISS check digit calculated?
Does this tell me who a NISS belongs to?
What does the first digit mean?
Is a formula-valid NISS a real one?
How do I get a NISS if I do not have one?
- Segurança Social · Número de Identificação de Segurança Social (NISS) ↗The body that issues and manages the NISS.
- Segurança Social Direta ↗Official portal: log in with the Cartão de Cidadão, Chave Móvel Digital or a Segurança Social user account.
- Segurança Social · Guia Prático Pedido de NISS (v1.18) ↗Request lookup with ID, email and date of birth; NISS proof after a biometric check.
- Segurança Social · Guia Prático Pessoa Singular, Alteração de Dados ↗The Perfil > Dados Pessoais menu of the Segurança Social portal.
- Segurança Social · Contactos e Canais de Atendimento ↗Helpline 210 545 400 / 300 502 502 and appointment booking on Siga.
- Lei n.º 7/2007 (Cartão de Cidadão), art. 7.º e 16.º ↗The NISS is a visible element of the card; the NIF and NISS databases cannot be cross-matched without legal or CNPD authorisation.
- Código do Trabalho, art. 276.º, n.º 3 ↗A payslip must show the Segurança Social registration number.
- gov.pt · Ativar a Chave Móvel Digital ↗Activation with your NIF and Portal das Finanças password; the temporary PIN arrives by post.
- gov.pt · Consultar números de identificação para estrangeiros ↗Where foreigners look up the NIF, NISS and número de utente (health user number) they requested.