This report is the eleventh edition of the OECD's Tax Administration Series. It provides internationally comparative data on aspects of tax systems and their administration in 58 advanced and emerging economies. The report is intended to inform and inspire tax administrations as they consider their future operations, as well as to provide information on global tax administration trends and performance for stakeholders and policy makers. The report is structured around nine chapters that examine the performance of tax administration systems, using an extensive data set and a variety of examples to highlight recent innovations and successful practices. This edition also contains an additional chapter that explores progress on the digital transformation of tax administrations. The underlying data for this report comes from the International Survey on Revenue Administration and the Inventory of Tax Technology Initiatives.