The Hague Convention Abolishing The Requirement of Legalization (Authentication) for Foreign Public Documents is an international treaty signed by more than 90 nations, including the United States, which makes it easier for notarized documents from one country to be accepted by another.
The treaty allows member nations to authenticate notarized international documents with a single attached form called an apostille. In the United States, apostilles are usually issued by a state Notary-regulating agency such as a Secretary of State's office. Without an apostille, notarized documents must be authenticated through a slower, less-efficient process involving multiple government agencies.
Clients may occasionally ask you about obtaining an apostille. While you can refer them to your state's Notary-regulating agency, it is not your responsibility to obtain an apostille on their behalf.