This study retraces the history of tax compliance in Italy from unification to today. We review the attempts at evaluating the gap between actual and potential tax revenue, from nineteenth-century descriptive statistics up until the formal estimates of recent decades, which distinguish lawful tax erosion from avoidance and evasion. Secondly, we analyze the explanations given and solutions proposed to increase tax compliance, grouping them into five "theses": excessive tax burden, structural deficiencies in specific taxes, inefficiency of tax administration, taxpayers' reluctance and the complexity of tax laws. We also assess the changing attitudes of taxpayers towards tax and the tax authorities over the same period. The excursus shows that compliance problems are a long-term constant of the Italian tax system, even if their scale has diminished over time, at least in percentage terms. The problems have always originated from a specific group of taxpayers (self-employed workers and sole proprietorships). On the other hand the causes, and therefore the solutions to be taken into consideration, are complex and multifaceted.