Apply for a negative certificate (for citizenship)
Source: BUS Rheinland-PfalzIf you require official proof that you do not have German citizenship, you can apply to the citizenship authority for a declaration of non-existence of German citizenship. If it can be established that you do not have German citizenship, a so-called negative certificate will be issued.
You will need a negative certificate, for example, if you have been asked by an authority abroad (e.g. in your country of origin or in your parents' country of origin) to provide official proof that you do not have German citizenship or if this is required in order to use the consular services of another country's diplomatic mission in Germany.
A negative certificate is often required, for example, if you were born in Germany, are descended from German ancestors or have lived in Germany for a very long time.