The document which is used by Croatian king Zvonimir to give people from Brač right to free trade is considered to be a forgery. Scientists who have studied that issue, already found lot of arguments for that thesis. While, there is still controversy about authentication of some other documents of the king Zvonimir, this one is considered by most of the scientists to be a forgery. In this thesis has been done diplomatic and philological analysis of the problem and also comparison to the other documents of the king Zvonimir. This thesis also provides insight on the historical and political conditions that were current at the time of issue of the document. The results coincide with previous findings. It was noted too many discrepancies in diplomatical analysis of the document, in philological analysis and comparison with other Zvonimir's documents has been observed that some names and forms written in this way can only be founded in this document, and the historical context is such that there was no real need for the release of the document. All this unequivocally indicates that this document is forgery, and that was probably created because of the historical and political need at later period.