This chapter deals with the evolution of tax administration in Spain from the initial stages of the democratic process, way back in the second half of the seventies, up to the present time. Given the relevance of the classical interrelation between the tax reform processes and tax administration reforms, we review the main events and milestones in the last three decades. We analyze the influence that institutional, economic, and political factors have had on both the architecture of the tax administration and its organizational behavior. Nevertheless, based on what we have just said, the performance of the Spanish tax administration cannot be satisfactorily assessed without explicit reference to the deep decentralization experienced by the Spanish tax system from the early eighties, and especially since 1994. That is why a considerable part of the chapter is devoted to analyze the role played by the successive reforms of the Autonomous Communities' financing system, and the decisions of the regional governments themselves, in shaping Spain 's tax administration.
