This is the fourth edition of Tax Policy Reforms: OECD and Selected Partner Economies, an annual publication that provides comparative information on tax reforms across countries and tracks tax policy developments over time. The report covers the latest tax policy reforms in all OECD countries, as well as in Argentina, Indonesia and South Africa. Monitoring tax policy reforms and understanding the context in which they were undertaken are crucial to informing tax policy discussions and to supporting governments in the assessment and design of tax reforms.