According to Belgian law, an authentic instrument is proof of its content, which are elements noted and verified by the competent authority. It is binding on the parties, on third parties and on judicial authorities. It is only possible to prove the contrary in a complex procedure similar to the procedure for challenging a judicial decision on the grounds of judicial bias: the procedure to challenge the authority of a document.
Authentic are: the date, the place where the instrument was drawn up, the fact that the parties have appeared before the notary, that they have made a number of declarations in his/her presence, that they have made certain payments, etc. However, any references the veracity of which the public officer was unable to ascertain in person and which have only been included in the instrument on the basis of the parties’ declarations, are only evidenced by the authentic instrument until the contrary is proven according to the rules of ordinary law (Art. 1319-1320 C.C. and Art. 895 et seq. of the Judicial Code).