The aim of this chapter is to study how the French tax administration perceived and assessed voluntary evasion of income tax between its introduction in July 1914 and the strengthening of tax control capacities in the 1970s. The chapter begins with the inter-war period, which was marked by the need for reconstruction. The fall in economic activity, the generalisation of the black market and the patriotic basis of the refusal to pay taxes doomed these reforms. After the troubles of the Liberation, the re-establishment of democratic institutions and the massive involvement of the State in the reconstruction and organisation of the social state forced a reaction. However, the system remained deeply unequal, with labour income that could not be hidden being the most taxed, while part of the income from capital escaped taxation. The increase in tax revenues and in tax adjustments are more the result of the economic and social transformations of the 1950s and 1960s than of the increase in funds allocated to the fight against fraud. The cross-checking of information on taxpayers and the exemplary nature of controls reduced fraud and improved tax yields, but without making them more equitable.