German labor law deliberately protects the anonymity of trade union members from reprisals by the employer. It is therefore important that the employer has no general right to ask about your trade union membership, either before the employment relationship or during your employment with the company.
Only in a few individual cases, where there is a justified objective interest, may the employer ask about your membership of a trade union. These are rarely the case in everyday employment law. If you have any doubts about your specific situation, we recommend that you seek legal advice.