# What is modelo TA.1?

> Modelo TA.1 is Social Security's form for affiliation, a Social Security number, or a change of data. It is not the autónomo alta.

- Page: https://autonomo.eus/blog/what-is-modelo-ta1
- Last checked: 22 October 2026

Short answer. The steps are on the guide.

Modelo TA.1 is a Social Security form for affiliation, for assigning a Social Security number, and for a change of data. **It is not the form for the self-employed alta.** The alta is a different Import@ss service, Alta en trabajo autónomo.

## What it is

The [list of worker forms](https://www.seg-social.es/wps/portal/wss/internet/Trabajadores/Afiliacion/10817/31190) includes "Form TA1 - Application for Social Security affiliation, a Social Security number or change of data". That is the title on the list. The same list has many other TA forms, for employed workers, for seafarers, for special agreements and for other schemes. It does not present TA.1 as the self-employed registration.

The [Import@ss page for requesting a Social Security number](https://portal.seg-social.gob.es/wps/portal/importass/importass/Categorias/altas%2C+bajas+y+modificaciones/altas+y+afiliacion+de+trabajadores/solicitar+el+numero+de+la+seguridad+social) uses the Spanish name "Solicitud de número de la Seguridad Social y variación de datos (Modelo TA.1)". It names that form in a specific place: if the NUSS is for a child, the mother, the father or the legal guardian presents the request, and one of the documents they must provide is the modelo TA.1 completed with the child's details, together with a photo of the child's DNI, NIE or passport and a copy of the family book or a document that proves parental authority or guardianship. The page recommends downloading the documents linked to the procedure and filling them in before you sign in. It lists "Solicitud de número de la Seguridad Social y variación de datos (Modelo TA.1)" among those documents.

The [Social Security magazine](https://revista.seg-social.es/-/como-obtener-el-nuss-numero-de-la-seguridad-social-1) names the same form in a different situation. If you do not have the identification methods it has just described, it says you can still request the procedure online through Import@ss, and it lists Modelo TA.1 among the things you will need, next to your identity document, an email address and a device with a camera. The magazine and the Import@ss page are not the same sentence. One names TA.1 for a child's application. The other names it when you lack those identification methods. This answer does not merge them into a single rule about when an upload is required.

What the number is, and the fact that the request is a different service from the alta, is [What is a NUSS?](https://autonomo.eus/blog/what-is-a-nuss). The [practical guide](https://portal.seg-social.gob.es/wps/portal/importass/importass/Colectivos/trabajo+autonomo/guia) says the self-employed alta needs your NUSS or NAF. It does not tell you to post modelo TA.1 as that alta. The alta service is [Alta en trabajo autónomo](https://portal.seg-social.gob.es/wps/portal/importass/importass/Categorias/altas%2C+bajas+y+modificaciones/altas+y+afiliacion+de+trabajadores/alta_trabajo_autonomo), whose button is "Solicitar alta". The form name people still search for as the old alta, TA.0521, is not this form. It is [What is modelo TA.0521?](https://autonomo.eus/blog/what-is-modelo-ta0521).

The forms list was opened on 22 October 2026. Its TA.1 entry is the affiliation, number and change-of-data application. It does not add a second title that would make TA.1 the autónomo alta.

## What is different in Euskadi

Modelo TA.1 is a Social Security form. The worker-forms list and the Import@ss pages do not publish a different TA.1 for Álava, Bizkaia or Gipuzkoa. Your Hacienda Foral has its own censuses and its own models. Those are not TA.1. The Social Security number the form is about is the same NUSS in all three territories.

## Where to read the steps

The number, including the case of a child, is [Get your Social Security number](https://autonomo.eus/steps/social-security-number). The self-employed alta, which is not this form, is [Register with Social Security](https://autonomo.eus/steps/register-social-security).

## Official sources

- [Social Security: worker forms, including TA.1](https://www.seg-social.es/wps/portal/wss/internet/Trabajadores/Afiliacion/10817/31190)
- [Import@ss: request a Social Security number](https://portal.seg-social.gob.es/wps/portal/importass/importass/Categorias/altas%2C+bajas+y+modificaciones/altas+y+afiliacion+de+trabajadores/solicitar+el+numero+de+la+seguridad+social)
- [Social Security magazine: how to obtain the NUSS](https://revista.seg-social.es/-/como-obtener-el-nuss-numero-de-la-seguridad-social-1)
- [Import@ss: practical guide for self-employed work](https://portal.seg-social.gob.es/wps/portal/importass/importass/Colectivos/trabajo+autonomo/guia)
- [Import@ss: alta in self-employed work](https://portal.seg-social.gob.es/wps/portal/importass/importass/Categorias/altas%2C+bajas+y+modificaciones/altas+y+afiliacion+de+trabajadores/alta_trabajo_autonomo)

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