• The date on which the authentic instrument was drawn up
• The place where the authentic instrument was drawn up
• The signature by the parties of the authentic instrument
• The parties’ declarations
• Any observation made by the authority within the limits of its competence
• The measures the authority declares to have taken
• Appearance, identification and consent of the parties

Before which authority: It can be contested before Courts of the Republic of Bulgaria
According to which procedure (state the applicable rules): Challenging the authenticity of a document is possible before civil courts following the regulations of the Civil Procedure Code. It is provided within the following provisions:
Art. 193. (1) Interested parties may challenge the authenticity of the document at the latest with the response of the legal proceedings. When the document is presented at a court hearing, the challenge shall be made at the latest at the end of the hearing.
(2) The Court orders verification of authenticity of the document if the other party declares a wish for such a verification. (3) The onus of proving the document is not authentic is on the party which challenges it.
Art. 194. (1) The Court carries out a verification by comparison with other undisputed documents, by questioning witnesses, or by experts. (2) After the verification the Court issues its judgment as to whether the document is authentic or not authentic. In the latter case, the Court excludes the document from the evidence and sends it to the Prosecution together with a copy of its conclusion.
Within what timeframe: Art. 193. (1) Interested parties may challenge the authenticity of the document at the latest with the response of the legal proceedings. When the document is presented at a court hearing, the challenge shall be made at the latest at the end of the hearing.