The article presents the modeling mechanism of the error determination when making financial decisions in conditions of uncertainty and risk. Researched modeling is based on using the assessing of the diagnosed level of enterprises' economic security with help of mathematical description and calculations of probability transitions matrix and using the research method, the method of direct and reverse interpolation, averaging, statistical and index method, root mean square error method, simulation modeling, probability theory method, matrix method, etc. It has been studied that the most difficult is the process of modeling financial decision-making in conditions of uncertainty, since due to various types of risk there is a high threat of insufficiency or inaccuracy of information that distorts technical calculations, the indicator of which is real financial costs and timely detection of permissible and unacceptable deviations of parameters.