The influence of economic ideas in parliamentary debates has attracted increasing attention in the analysis of the institutionalisation of political economy in the liberal age in the Western world. Within this framework, this paper explores a particular case: the relevance of economic ideas and the role of economists in the debates that took place in the Spanish Parliament in 1869 following the bill issued by the Minister of Finance Figuerola to establish a tax on personal incomes. Economic ideas and parliamentarian economists played a significant role in the design of the income tax as a key tool to modernise Spain's tax system, and in the subsequent parliamentary discussions.
