Why would a birth certificate have a notary stamp on it in New York?

In the state of New York, and other states, a birth certificate may need to be authenticated by a notary stamp during an apostille process. A birth certificate that is going to a foreign country that is bound by the 1961 Hague Convention requires an apostille agent to authenticate it.

In New York State, obtaining an apostille for a birth certificate is a three-step process. In the first step, a person obtains a copy of the birth certificate from Vital Records. Next, the certificate must be authenticated by the New York County Clerk's office. The final step is securing the apostille authentication, which is done through an application process.