The rational functioning of the tax system is a significant problem for any state. Evaluation of the tax system performance is usually carried out considering interest only of one part – either government or business or related to the specific narrow parts of the tax system, like an analysis of a particular tax, thus not allowing to perform a full-fledged assessment. One of the problems that are crucial for the tax system’s vitality – is its reliability.
The purpose of the article is to develop an approach of estimating and assessing the tax system reliability. Another two major criteria of the tax system functioning are equity and efficiency, which form the basis of the tax system optimization for finding their rational combination. The process of such multi-criteria optimization is usually associated with irreducible incomparability of the criteria.
Methodology – as a tool proposed Weibull distribution, S-shaped curve, as well as a three-tiered scale for determining the level of the tax system reliability. Using Kendall’s Concordance Coefficient, the resulted data was processed and taxes and criteria on which concessions could be made were determined.
Findings – the analysis has shown that the difference between the opinion of experts regarding the ranking of taxation criteria was related to their affiliation – state or business. To find a solution in this case method of successive concessions has to be applied, which requires a ranking of relative single indexes of taxation criteria, as well as taxes that are associated with them.
Originality – for formalization of the process of dealing with incomparability of criteria, proposed concepts of business-oriented aspect of tax optimization, which is aimed at both business entities, as well as on individuals and state-oriented aspect of tax optimization.