How to Get a Spanish Social Security Number (NUSS): Complete Step-by-Step Guide

Until 2023, only paid internships were affiliated to the Spanish social-security system. Real Decreto-ley 2/2023 (in force since 1 January 2024) extended affiliation to all non-laboral practical training, including university Erasmus+ traineeships and VET work-based learning. The 2026 General State Budget (Ley 31/2025) confirmed the regime and updated the reduced-contribution amounts.

• Paid internships — full ordinary contribution (split host/intern) on the actual stipend.
• Unpaid internships — symbolic flat-rate contribution of €2.54 per day (2026 figure) paid entirely by the host.
• The intern is now counted in the host's Régimen General workforce for occupational-accident cover from day one.
• Universities and VET centres remain co-responsible for verifying that the host has filed the declaration.

Practical consequence for incoming Erasmus+ interns: even an unpaid 2-month placement now triggers a Spanish social-security number request. The NIE alone is no longer enough.

• NIE — your Spanish foreigner identification number (see our NIE guide). Permanent, mandatory for all interns.
• NUSS (Número de la Seguridad Social) — your Spanish social-security number. Issued once by the TGSS; reused for any future job in Spain.
• A1 (PDA1) — portable document issued by your home social-security institution proving you remain affiliated at home during a short posting. Used to AVOID double affiliation when applicable.

The A1 does NOT replace the NUSS in Spain after the 2024 reform when you are physically working on Spanish territory under a Spanish host's direction. The NUSS is required for the host's TGSS declaration; the A1 only prevents the contribution from being collected twice.

There are three filing channels. Pick the one that fits your situation; all three produce the same NUSS in the same database.

• Channel 1 — Sede Electrónica with Cl@ve PIN or digital certificate. Fastest if you already have Cl@ve.
• Channel 2 — In person at any Centro de Atención e Información de la Seguridad Social (CAISS), with prior cita previa.
• Channel 3 — The host's HR team files form TA.1 on your behalf via Sistema RED. This is the most common path for Erasmus+ interns.

• Form TA.1 — Solicitud de Número de la Seguridad Social, completed in Spanish.
• Passport copy (data page + entry stamp).
• NIE certificate (Certificado UE for EU citizens or TIE for non-EU).
• Convenio de Prácticas (internship agreement) signed by the host, the university and the intern.
• European Health Insurance Card or private health insurance certificate.

A1 is not a documentary requirement for the NUSS itself — only for exemption from the contribution. File the A1 separately with your home institution before you arrive.

• Paid placement — ordinary contribution ~28.3% of the stipend, split between host (~23.6%) and intern (~4.7%).
• Unpaid placement — €2.54/day flat rate, paid 100% by the host, with a 95% reduction (so effective cost ~€0.13/day).
• Intern share is deducted from the stipend on the payslip; the host files form TC1 monthly.
• EU interns with an active A1 are exempt from the intern share; the host still files the declaration but reports the exemption code.

• Coverage for workplace accidents and occupational disease from day one (Accidentes de Trabajo y Enfermedades Profesionales).
• Access to the Spanish public healthcare network if your placement is over 90 days and you also register at the local Centro de Salud.
• Pension-contribution time accrues toward your future pension under EU coordination (Regulation 883/2004).
• If the host pays you, you can request the U1 portable document at the end of the placement to carry unemployment-insurance time back home.

• Filing TA.1 with the passport number instead of the NIE — the system rejects it 100% of the time.
• Confusing NUSS with NAF — older payroll software refers to the same number as NAF; both are valid.
• Assuming the A1 exempts you from the NUSS — it does not.
• Hosts skipping the unpaid-placement declaration because 'there is no salary' — Inspección de Trabajo audits in 2025 fined more than 4,200 hosts for this.

• Ask the host to file the baja (deregistration) in Sistema RED on your last working day.
• Download your Vida Laboral certificate at sede.seg-social.gob.es to prove your Spanish contribution history.
• If you were paid, request the U1 portable document if you plan to claim unemployment back home within 5 years.
• Keep the NUSS — you will reuse the same number for any future paid work or internship in Spain.

The NUSS request fails at validation, not at judgement. Every rejection we see comes from starting before one of these four things exists.

• A valid NIE. The TGSS system matches your identity against the Extranjería database — a passport number alone is rejected. Get the NIE first (see our NIE guide).
• A signed Convenio de Prácticas naming the host, the university, the dates and the weekly hours. It is the legal basis for the filing.
• An address in Spain for notifications. It can be your host's address at the start, but keep it consistent across the NIE and the NUSS files.
• A contactable email and Spanish or EU mobile number — Cl@ve PIN and the Importass confirmation both send codes by SMS.

You do not need a Spanish bank account, an empadronamiento certificate or a tarjeta sanitaria to obtain the NUSS. Those come after, and several of them depend on the NUSS existing first.

The Tesorería's Importass portal has a dedicated flow for people who have never been registered in the Spanish system. It works with a simple identity check by SMS, so you do not need a digital certificate or Cl@ve to use it.

1. 1
   1. Open the right service

   Go to Importass → 'Trámites' → 'Números de la Seguridad Social y afiliación' → 'Solicitar número de la Seguridad Social'.

2. 2
   2. Choose the identification method

   Select 'Vía SMS' if you have no certificate or Cl@ve. You will be asked for your NIE, date of birth and a mobile number, and you receive a one-time code.

3. 3
   3. Fill in the identity block

   Surnames and given names exactly as on the NIE certificate — not as on the passport if the two ever differ. Nationality, sex, date and country of birth, and your parents' names (the form asks for them; use the passport spellings).

4. 4
   4. Fill in the address block

   Type of street (Calle, Avenida, Plaza), name, number, floor and door, postcode, municipality and province. The postcode drives the assignment of your CAISS office, so get it right.

5. 5
   5. Upload the supporting documents

   Scan or photograph the NIE certificate, the passport data page and the signed Convenio. PDF or JPG, under 5 MB each.

6. 6
   6. Submit and save the receipt

   The portal issues a 'justificante' PDF with a registration number. Download it immediately — it is your proof if the NUSS is delayed.

7. 7
   7. Collect the number

   The NUSS normally arrives by email or appears in Importass within 1–3 working days. It looks like 28/12345678/90 — province code, sequential number, check digits.

Any Spanish company with employees already has Sistema RED credentials and an authorised gestor. For an intern this is the fastest and least error-prone channel, because the host's gestor files dozens of these a year.

Practical note for coordinators: institutions are co-responsible for verifying that the host filed the declaration. Asking for the RED confirmation as a standard onboarding artefact removes almost all downstream disputes.

1. 1
   1. Send HR a single email

   Attach the NIE certificate, the passport data page and the signed Convenio, and ask explicitly: 'Could you please request my NUSS via TA.1 in Sistema RED and send me the number?'

2. 2
   2. Confirm who files

   In many companies payroll is outsourced to a gestoría. Ask for the gestoría's contact so you are not stuck in an internal email chain.

3. 3
   3. Wait one working day

   TA.1 through RED usually returns the NUSS the next working day. If nothing arrives in 48 hours, chase — filings sometimes sit unsent in a draft queue.

4. 4
   4. Ask for the alta confirmation too

   Getting the number is only half the job. Request the RED confirmation of your alta (registration) showing the start date, the CCC (host's contribution account code) and your NUSS.

5. 5
   5. Verify it independently

   Do not rely on the host's word: check your own record (next section) before your first day.

Use this only if the online route rejects your identity or your host has no RED access. It is slower but it is the one channel that can resolve a mismatched identity record on the spot.

1. 1
   1. Book the cita previa

   Sede Electrónica de la Seguridad Social → 'Cita previa para pensiones y otras prestaciones' → choose 'Afiliación e inscripción' → 'Solicitud de número de Seguridad Social'. Slots are usually available within 1–2 weeks.

2. 2
   2. Prepare the folder

   Printed and signed TA.1, NIE certificate plus copy, passport plus copy, signed Convenio plus copy. Bring originals and copies for each.

3. 3
   3. Attend

   Say clearly: 'Vengo a solicitar el número de la Seguridad Social para unas prácticas Erasmus+.' The clerk validates the identity data against the Extranjería record.

4. 4
   4. Collect the resolution

   In most offices the NUSS is printed and handed over during the appointment. If the record needs manual validation, you receive it by post or email within 10 working days.

TA.1 is 'Solicitud de afiliación / número de la Seguridad Social'. Even when the host files it, read it before signing — you are the one legally declaring the data.

• Section 1 — DATOS DEL SOLICITANTE: NIE (never the passport number), surnames, given names, sex, date and country of birth, nationality, and parents' names.
• 'Tipo de documento': choose 'NIE' and copy the letter-digit-letter sequence exactly, including the trailing check letter.
• Section 2 — DOMICILIO: full Spanish address with postcode. This determines your assigned CAISS and where paper notifications land.
• Section 3 — DATOS A EFECTOS DE NOTIFICACIÓN: tick electronic notification and give an email you check; otherwise everything goes by post.
• Section 4 — SOLICITA: tick 'Asignación de número de la Seguridad Social'. Do not tick 'Afiliación' if you already hold a NUSS from a previous stay — you would be requesting a duplicate, which is refused.
• Signature block: place, date and your handwritten signature. A scanned signature is accepted only when the host files digitally through RED.

Having a NUSS does not mean you are affiliated. Affiliation is the host's separate 'alta' filing, and it is the part that goes wrong. Two free documents prove it, and you can pull both yourself.

• Informe de Situación Actual del Trabajador — shows whether you are currently in alta, with which company (CCC) and since when. This is the document to check in your first week.
• Informe de Vida Laboral — the full history of every day contributed in Spain. Use it at the end of the placement as proof of contribution time.
• Both are downloadable at Importass → 'Informes y certificados', using Cl@ve, digital certificate or the SMS identification route.
• If the report says 'sin datos' or 'situación de baja' during your placement, the host has not filed the alta — raise it the same day with HR and your university coordinator.

An intern working without an alta is uninsured for workplace accidents, and the host is exposed to an Inspección de Trabajo penalty. Checking a one-page PDF in week one protects both sides.

Cl@ve is the Spanish e-government identity system. You can obtain the NUSS without it, but you will want it for the Vida Laboral, tax filings and the health-card process.

1. 1
   1. Choose the registration method

   'Cl@ve PIN' (single-use code by app/SMS) covers everything an intern needs. 'Cl@ve Permanente' adds a password and is only needed for repeated filings.

2. 2
   2. Register

   Online with an invitation letter code, online with a digital certificate, or in person at any AEAT or Seguridad Social registration office — the in-person route is instant and needs only your NIE and passport.

3. 3
   3. Activate

   Install the Cl@ve PIN app or register your mobile number, then test the login on Importass before you actually need it.

4. 4
   4. Alternative: digital certificate

   The FNMT certificate is issued free, requires one in-person identity check, and installs in your browser. It is more robust than Cl@ve for foreigners whose mobile number changes.

The NUSS is a key that opens three other doors. Do these in order once the number is issued.

Erasmus+ grants themselves are not employment income and are not contributed on. Only the host-paid stipend enters the base de cotización.

1. 1
   1. Register the address (empadronamiento)

   At the town hall with your passport, NIE and rental contract or host letter. Free, and required for the regional health card.

2. 2
   2. Request the tarjeta sanitaria

   At your local Centro de Salud with the NIE, NUSS and empadronamiento. Placements under 90 days can rely on the EHIC instead; longer placements should get the regional card.

3. 3
   3. Read your first nómina

   Check three lines: 'Base de cotización' (the stipend used for contributions), 'Aportación del trabajador' (your ~4.7% share) and 'IRPF' (income-tax withholding). If IRPF is withheld at a high rate, file form 145 with HR to declare your personal circumstances.

4. 4
   4. Keep the annual certificate

   In January the host issues a 'certificado de retenciones'. Keep it — you may reclaim withheld IRPF by filing a Spanish tax return if your total Spanish income is below the personal allowance.

NUSS / NAF

Your permanent Spanish social-security number. Two names, same number.

Alta

The host's registration of you as active in the system from a specific date.

Baja

Deregistration on your last working day.

CCC

Código de Cuenta de Cotización — the host's contribution account you are attached to.

Sistema RED

The electronic channel companies and gestorías use to file with the TGSS.

TGSS

Tesorería General de la Seguridad Social — the body that assigns the NUSS and collects contributions.

CAISS

The public-facing social-security offices where in-person filings are made.

Vida Laboral

The official report of every day you have contributed in Spain.

Convenio de Prácticas

The tripartite internship agreement that is the legal basis for affiliation.

• NIE issued and propagated (48–72 hours after the appointment).
• Convenio de Prácticas signed by host, university and intern.
• NUSS requested via Importass, host RED filing, or a CAISS appointment.
• NUSS received and stored (format 28/12345678/90).
• Alta confirmed in your Informe de Situación Actual del Trabajador in week one.
• A1 sent to the host's payroll if you hold one.
• Empadronamiento done and tarjeta sanitaria requested for placements over 90 days.
• First payslip checked: base de cotización, worker share, IRPF.
• Baja filed on the last day and Vida Laboral downloaded the day after.
• U1 requested if you were paid and may claim unemployment at home within five years.