Fiscal capacity is regularly linked to warfare and democratization. However, the majority of income taxes - a cornerstone of government finance - were introduced by non-democratic states in peacetime. This paper is concerned with how autocratic politics shape the adoption and expansion of income taxes. Political institutions help overcome a commitment problem related to investments in taxation. To avoid being deposed by his or her elite supporters, a ruler needs to guarantee that new taxes will not be used opportunistically (e.g. expropriating the elite). If the elite supporters can effectively monitor the government, any transgressions will be detected and punishable. Institutions such as legislatures solve this commitment problem when they allow oversight and monitoring over the executive branch. The empirical implications are straightforward: in places with strong institutional oversight, which allows the elite to monitor the executive, we should observe higher fiscal capacity. I find support for this by analyzing newly available historical datasets over tax revenues, tax introduction dates, and political institutions.