This dissertation is a study of the impact of the transformation of the Late Roman Empire’s tax system on the economies of Sicily and southwest Anatolia. I focus on taxation as this was the primary aspect of imperial rule that affected the empire’s non-elite subjects. The Roman tax system was distinguished from that of the later Byzantine period by the interregional redistribution of taxed agricultural products for the purpose of state-organized urban and military supply. To accomplish this process of fiscal supply, the Roman state stimulated the creation of exchange networks linking agriculturally productive regions with the Mediterranean world’s largest pools of demand for surplus produce: the empire’s capitals at Rome and Constantinople and the standing armies concentrated along its borders. I contend that, through the creation of these new exchange networks, the Late Roman tax system had the potential to indirectly stimulate connectivity and a process of commercialization. To determine whether and how this potential was realized, I turn to the archaeological evidence from two case study regions, Sicily and southwest Anatolia, which were important sources of tax revenues for the supply of Rome and Constantinople, respectively. I employ a six-pronged methodology to reconstruct how the transformation of the tax system affected commerce across the 4th-8th centuries, drawing on syntheses of urban excavations, rural survey data, evidence for amphora production, the distribution of amphora exports, shipwreck cargos, and the distribution of imported and local pottery. This analysis reveals that the tax system indirectly stimulated a shift towards increasing market orientation in agricultural production and consumption patterns alongside a concomitant intensification of trade in both Sicily and southwest Anatolia. The gradual cessation of state-driven redistribution across the 5th-7th centuries precipitated a sharp decline in trade, although the residual impact of the tax system remained visible in the shape of the exchange networks that remained.