This is an administrative act by which the Social Security Treasury Office recognises the inclusion of a physical person in the Social Security System who carries out an activity for the first time that gives rise to inclusion in the scope of the System.

Any person who begins a work activity included in a Social Security System scheme must apply for an affiliation number.

The characteristics of the affiliation are the following:

It is required for people included in the System with regard to contributory type rights and responsibilities.

It is unique and covers all the System's Schemes.

It covers the entire life of the person included in the System.

It is exclusive.

The Affiliation application is made on form TA.1 "Affiliation/Social Security Number Application". If you have a digital certificate you can process the application directly via the Social Security number assignment service at the e-Office.

The Social Security Treasury General assigns a Social Security Number to each citizen to identify them in their relations with the System. It is also assigned to the beneficiaries of pensions or other benefits from the System.

The Social Security Number has the following characteristics:

All citizens require it prior to requesting affiliation and active contributor status in any Social Security scheme.

It is required for beneficiaries of pensions or other benefits from the System.

It shall be recorded in a Social Security Treasury General Decision, which will include their full name and DNI.

For affiliates, it is the same as their affiliation number.

Applications for a Social Security Number are made on form TA.1 "Affiliation/Social Security Number Application".

Affiliation in the Social Security may be carried out in the following way:

Initiated by the Employer

Employers are required to request affiliation in the Social Security System for those who enter into their service and are not already affiliated.

Initiated by the Worker

Self-employed workers, or similar, who begin working as such and who are not already affiliated, are required to request affiliation.

Likewise, workers employed by another person, or similar, whose employer does not comply with the obligation indicated in the previous section, may request their own affiliation in the System.

Initiated by the Administration

Affiliation may be carried out through the initiative of the Provincial Departments of the Social Security Treasury General or its administrative offices when a Social Security and Employment Inspection of the data held by the management entities, or any other procedure, detects a failure to comply with the obligation to request affiliation on the part of the workers or the employers who are required to do so.

The affiliation application (form TA.1 ) is submitted to the Provincial Department of the Social Security Treasury Office or its Administration office in the province in which the company in which the worker or assimilated worker provides services, or in which the self-employed worker is established.

 The affiliation applications must be made prior to providing services as a worker employed by another person.