We conduct an empirical study on the determinants of the psychological costs of tax evasion, also known as tax morale. As a preliminary step, we build a model of tax evasion including non-monetary considerations, show the relationship between tax compliance and tax morale. In the empirical analysis of tax morale we find, using a binomial logit model, that the justification of tax evasion can be explained by the presence of grievance in absolute terms (those who feel that taxes are too (...) high, those who feel that public funds are wasted, and those who accept underground economic activities); and grievances in relative terms (the suspected level of others’ tax evasion). The sense of duty and the level of solidarity are also relevant factors, but to a lesser extent. (shrink)