This paper explains a new method of a company's overheads allocation and a model of business decision making, both of which are based on the predicted future outcome value theory. The aim of the paper is to prove that business efficiency of a company's segments at all levels can be measured for shorter time periods (months) applying the rule of economy of scale, which can resolve the problems that the traditional VBC and a more contemporary ABC approach for business efficiency measurement cannot achieve when used for overheads allocation for short time periods. The first hypothesis set up in the paper is that VBC and ABC approach can allocate a company's overheads opposed to the rule of economy of scale when all common costs for a certain period are allocated. The second hypothesis is that the proposed model and method can be used to measure and control a company's overheads. The third hypothesis is that the model and method can be used to measure the efficiency of each company's segment as well as the whole company for a one-month period. The model and method were applied to a trading multi-segment company. The method used in the dissertation is a case study. The results achieved by the model and method prove that working hypotheses are true and applicable for measuring the efficiency of business segments for shorter time periods. The introductory part of the paper explains the basic scope of the research and how it can be linked to entrepreneurship. Then it reviews the most important results of managerial accounting history, sets research hypotheses, defines the scientific contribution of the paper, and explains its structure and basic concepts. The second chapter defines the research method and the aims of the paper. The third chapter explains the theory of predicted future outcome, based on which the fourth chapter defines a firm as a business system from the holistic point of view. The fifth chapter clarifies the model for business decision making and the method for common cost allocation. The sixth chapter describes a business case to which the model and method were applied, whereas the seventh chapter brings the results of the model and method application. The eighth chapter contains the analysis of results, and the final chapter presents the final consideration regarding the new model and method as well as the recommendations for further research.