Background: Using a variety of alternative accounting policies brings about different effects on the stated business results and the value of the company. Objectives: The objective of this paper is to develop a fuzzy logic solution for determining bias in financial reports on low-activity financial markets, and to find a method applicable to unquoted entities. Methods/Approach: A fuzzy logic system was developed using data on Croatian companies, the MatLab software, and the Mamdani fuzzy inference method. Results: The paper provides the summary of results obtained using a fuzzy logic system, and they indicate that the model has relevant validity. Conclusions: The model can serve as a stimulus for more detailed studies of biased financial statements elements. The fuzzy logic model should be further tested on a larger sample of companies classified based on their activity and under different business conditions.