The eighth edition of the OECD's Tax Administration Series, this report provides internationally comparative data on aspects of tax systems and their administration in 58 advanced and emerging economies. The publication presents the results of the 2018 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. For the 2018 survey round, the Asian Development Bank (ADB) agreed to participate along with the four partner organisations. The report has three parts. The first contains four chapters that examine and comment on tax administration performance and trends up to the end of the 2017 fiscal year. The second part presents ten tax administration-authored articles providing a country view on a range of topical issues to tax administration, while part three contains all the data tables that form the basis of the analysis in this report as well as details of the administrations participating in this report.