Tax and Social Security

Registering with Social Security

The difference between getting your Social Security number and actually being registered as active (alta) — and why both matter.

Last reviewed: 2026-06-15Registration (alta) generally needs to happen before or on the first day of activity — it isn't something to leave until afterwards.

This guide is not yet verified by Tuchati's editorial review — treat it as a helpful starting point, not a final legal answer.

Overview

Having a Social Security number (NUSS) isn't the same as being actively registered (alta) in the system. Registration is what actually activates your healthcare coverage and contribution record — it happens each time you start a job or period of self-employment.

Requirements

You must already have a NUSS (Social Security number) before you can be registered as active
For employees, your employer is legally responsible for registering you before your first day of work
For the self-employed (autónomos), you register yourself

Step-by-step process

Employees: confirm with your employer that they've submitted your alta before your start date — this is their legal obligation, not yours
Self-employed: complete your own alta as autónomo through the Social Security electronic office (RETA regime), typically alongside your Modelo 036/037 tax registration
Once registered, your healthcare coverage and pension contributions become active
When you stop working (change jobs, pause self-employment), a baja (deregistration) is filed — again, by your employer if you're an employee, or by you if self-employed

Required documents

NUSS (Social Security number)
Employment contract, if registering as an employee (though this is your employer's responsibility)
Modelo 036/037 tax registration, if registering as self-employed

Common mistakes

Starting work without confirming your employer has actually filed your alta — this leaves you without active coverage in the meantime
Assuming having a NUSS number alone means you're covered — you need active alta status, not just the number

Practical tips

You can check your own alta status online via the Social Security's electronic office, using your digital certificate or Cl@ve
If you're self-employed, your alta as autónomo has real deadlines tied to when you start actually trading — don't delay it once you've begun

How Tuchati can help

If you're unsure whether your registration is active, or you're navigating this as a first-time freelancer, Tuchati can help you check and understand next steps.