This paper aims to propose the approach to classify the industries in terms of easiness of tax evasion. Based on assumptions of taxpayer's behavior, our results allow defining the type of dependence of real tax rates on their nominal ones. We find that the graph, describing the taxpayer's behavior, has two key points: maximum - the optimal tax rate (if this rate increase, the real tax revenues fall), and also the point of simple reproduction (after achieving this level, firms stop to pay taxes at all with appropriate shifting into informal sector or closing down). I.e. two key levels of tax burden: optimal and zero can be defined. The values of those parameters for taxpayers operating in different groups of industries were calculated.