Duplicate of the affiliation card (Número de la Seguridad Social)

What you should have to hand

• DNI o NIE en vigor.
• Cl@ve (PIN or Permanente), certificado digital or DNIe. If not, a mobile with your number registered in the Seguridad Social for SMS.
• Email address.
• If you act for someone else: authorisation, DNIs and, if it's a minor, libro de familia or birth certificate.

Documentation

1. DNI/NIE: mandatory. If you use the no-certificate request, upload both sides.
2. Means of identification: Cl@ve, certificado or DNIe. SMS only works if the mobile is registered in TGSS.
3. Authorisation and proof of relationship: only if you represent another person (minors or adults with representation).
4. Contact details: email and phone to receive the PDF or notifications.

Step by step

1. Go to Import@ss: https://importass.seg-social.es.
2. Open Acreditaciones y certificados > Duplicado de documento de afiliación.
3. ID yourself with Cl@ve, certificado digital or DNIe. If you choose SMS, make sure your mobile is registered in TGSS.
4. Check your details (name, address) and hit Descargar. You will get an official PDF with your Número de Afiliación/Número de la Seguridad Social.
5. No ID options? In Import@ss, use Enviar una solicitud (sin certificado), pick Afiliación and request Duplicado de documento de afiliación. Attach DNI/NIE and explain you've lost the document. They will reply by email.
6. Prefer in person? Book cita previa TGSS at https://sede.seg-social.gob.es and, with your DNI, they'll print the duplicate for you at the counter.

Time-savers

• Use Cl@ve: it's instant. If you don't have it, registering via the app or videollamada usually beats waiting for postal registration.
• Update your mobile in Import@ss before using SMS. If it's not in their database, the code won't arrive and you'll waste time.
• Check your address in your Área Personal. If it's wrong, change it first and then generate the duplicate so it looks right.
• Download the PDF and upload it to your cloud. You'll be asked for it more often than you think (employer, GP, grants...).

Common mistakes to avoid

• Requesting “another number” instead of duplicado. Your NAF/NUSS is unique. Don't try to create a new one.
• Trying SMS ID without the mobile registered in TGSS: the code won't arrive and you'll lose the attempt.
• Going to the INSS: they don't do this; it's handled by TGSS. If you go in person, book at TGSS.
• Sending a no-certificate request without attaching the DNI: they'll return it asking for documents and you'll add days.
• Old browser or Autofirma badly installed for DNIe/certificado: use Chrome or Edge and have Autofirma updated if you use DNIe.