Abstract This paper examines some aspects of the decision to evade indirect taxes in the context of a monopolistic firm: in particular, the degree of interdependence between the tax shifting and the tax evasion decisions is analyzed both in the case of a fixed and of a variable probability of being detected. It is shown that, in the first case, the shifting and evasion decisions are separable, while, in the second case, this is no longer true; in this latter case, a rule according to which the probability decreases with larger declarations can be said to be an efficient one. The conditions for a firm's becoming a completely submerged one are derived and, finally, direct and indirect tax evasion are compared; it is shown that, for decreasing risk aversion, an indirect tax is evaded as a percentage less than a profit tax of equal yield.