Thesis: This thesis examines the role of the tax-and-benefit system on the income distribution, with a focus on labour incomes. Made of two parts, the thesis tackles three central questions for the economics of labour and taxation. The first question relates to the simple description of the distributional impacts of taxes. Second, economic actors paying the real cost of taxes might not be the ones paying it legally: assessing empirically the incidence of taxation is key for identifying their distributive implication. Third, the description of the distributional effects of taxes is further complicated by the fact that taxes affect behaviours. In particular, high income individuals may react more to taxes than the rest of the population. This distinction between the very top and the rest of the income distribution is the third major pivotal question of the dissertation.The first part of the thesis presents the methodology and the results of a microsimulation model of the French tax-and-benefit system. The first chapter offers a comprehensive description of the distribution of tax revenues according to the distribution of income. The second chapter proposes an evaluation of the main policy reforms taken in the aftermath of the 2008 financial crisis. It is based on a dual approach, encompassing both a macro and a micro analysis.The second part of the thesis focuses on the taxation process of labour incomes. The questions and the methods tackled are at the intersection of the public finance and the labour economics literature. The first chapter studies the overall wage distribution, emphasizing the role of social security contributions in the evolution of inequality. The last chapter looks at the impact of a wage tax at the very top of the distribution (top 0.003%, about 1500 individuals) on the wage setting process of top labour income earners. A quasi-experimental variation, the 75% tax on millionaires implemented in 2013 and 2014, and evaluation of public policies methods (difference-in-difference method) are used to document the incidence of the tax and the behavioural responses.