Form S1 for healthcare in another EU country other than the one to which you are insured

The S1 is basically Certificate previously known as E106, E109 and E121, that entitles you to health benefits in an EU country other than the one to which you are insured. It is useful for posted workers, cross-border workers, pensioners or civil servants and their dependents, and must be requested in the country where you are insured.

More importantly, the S1 is a necessary form when you applied, as a citizen of the European Unión in Spain, for your residency.