This report is the ninth edition of the OECD's Tax Administration Series. It provides internationally comparative data on aspects of tax systems and their administration in 59 advanced and emerging economies. The publication presents the results of the 2020 International Survey on Revenue Administration (ISORA), a multi-organisation international survey to collect national-level information and data on tax administration governed by four partner organisations: CIAT, the IMF, IOTA and the OECD. As with the previous survey round, the Asian Development Bank (ADB) also participated in ISORA 2020 along with the four partner organisations. The publication is structured around nine chapters that examine and comment on tax administration performance and trends up to the end of the 2019 fiscal year, and it includes a variety of examples supplied by tax administrations to highlight recent innovations and good practices. The publication also has two annexes containing all the ISORA 2020 data, which form the basis of the analysis in the report, as well as the details of the administrations that participated in this publication.