The Certificate of Naturalization is a document issued by the United States government as proof of a person having obtained US citizenship through naturalization. As this is a legal process for which an individual may obtain nationality and citizenship within the United States, this certificate shows that the process was followed and that the individual is in fact a citizen. The Certificate of US Naturalization is also known as the Form N-550 and serves as proof for any intended purposes. This can serve as a proof of citizenship and in some cases work as an identification source in cases where it may be necessary.