In 1961 many nations joined together to create a simplified method of "legalizing" documents for universal recognition in each other's countries. Members of the conference, referred to as the Hague Convention Abolishing the Requirement for Legalization of Foreign Public Documents (33 U.S.T 883), adopted a document referred to as an Apostille that would be recognized by all member nations.
Documents sent to member nations, completed with an Apostille at the state level, may be submitted directly to the member nation without further action.
Documents sent to non-member nations requiring a Certification of the signature of the state's public official at the state level, will need to be transmitted to the Office of Authentications of the U.S. Department of State in Washington, D.C. for the authentication of the State Official's signature if requested by the receiving country.
To read more! What is an Apostille certification? Source: InfoTaxSquare Business Documents Filing In All Fifty States!