How to Apostille a Document Apostille is the official form of authentication that is required to validate the use of documents outside the United States. Your document must be affixed with an Apostille stamp from the correct designated authority to be valid for use in any Apostille convention participating countries.   What is an Apostille Convention   The Hague Apostille Convention was held in the Hague “ the Netherlands” in 1961, to facilitate the complicated legalization ...