If both the state that issued the document and the “state of destination” in which the document is to be used are parties to the Hague Convention Abolishing the Requirement of Legalisation for Foreign Public Documents (Federal Law Gazette. No. 27/1968) and have not raised objections to the accession of the respective other state, no diplomatic authentication/legalisation of documents for legal relations is required. In such cases, documents from the issuing state must be authenticated by provision of an “apostille” by the designated authorities of the issuing state in order that they may be used in the state of destination.
An apostille is not an additional form of authentication/legalisation but replaces such authentication/legalisation. It does not require any further confirmation.
Further details on the Hague Convention and a list of Contracting States as well as objections raised against accessions to the Convention can be found on the website of the Permanent Bureau of the Hague Conference on Private International Law.