In recent decades, many countries around the world have become more fiscally decentralised. Spain provides a unique case study given it has relatively quickly transitioned from a highly centralised country to a much more decentralised country, although formally not a federation. As part of this decentralisation, autonomy over individual income tax rates and brackets was recently granted to the regions (Autonomous Communities), which are similar to states or provinces in other countries. In the early 2000s, individual income tax brackets and rates were the purview of the central government. Only recently were the Spanish regions granted the authority to levy their own individual income tax rates on a portion of the personal income tax base. Once granted this authority, marginal tax rates diverged substantially at the top of the income distribution, resulting in substantial tax differentials across various regions within Spain. This article reviews the economic consequences of Spanish fiscal decentralisation with a particular focus on the impact on the mobility of high-income individuals and the implications of migration decisions for public finances.