If you have previously been in Germany and were working, you were probably given a Social Security number ‘Sozialversicherungsnummer’
This is mandatory and is provided by the German Pension Office. It is necessary to be registered in Germany to apply for a German social security number, because the social security number can only be sent to a German address.
If you have received this number before, you can add it into our health insurance questionnaire. If not there is no problem too, you can omit it. All it does it help us receive more information on you.