We use a theoretical framework based on concepts of historical institutionalism, institutional logic and ideology to enhance understanding of how government accounting and taxation helped to institutionalize slavery in Brazil by interpreting enslaved people as an economic commodity. We conduct an interpretive critical analysis using archival sources from the period 1531–1888. The social practice of government accounting and taxation produced and conveyed meaning using symbolic forms that ranged from everyday statements to complex texts and images. These codified financial realities in a way that reified slavery and influenced the historical trajectory of slavery. Government accounting and taxation practices were self-reinforcing sequences. They encouraged a structural inertia that was not conducive to de-reification of the slave trade or of slavery. We reveal how government accounting and taxation institutionalized government administration of slavery by according it social authority, social reality and temporal endurance.