The A1 certificate is relevant for EU nationals who work temporarily in another EU country, Iceland, Liechtenstein, Norway, Uk, or Switzerland or in two or more countries at the same time and remain insured under the social security scheme of the home country (see “Einstrahlung” and “Ausstrahlung”). The A1 Certificate is a declaration concerning the applicable legislation and can be used as evidence for presentation to one’s employer, government agencies, etc., so as to avoid double insurance policies. It is issued by the health insurance provider or the responsible pension insurance carrier at the request of the employee, the self-employed worker, or the employer. The form has replaced the earlier E101 and E103 forms.
Source: Social security