Modern tax administrations seek to optimize tax collections while minimizing administration costs and taxpayer compliance costs. Experience shows that voluntary compliance is best achieved through a system of self-assessment. Many tax administrations have introduced self-assessment principles in the income tax law but the legal authority is not being consistently applied. They continue to rely heavily on “desk” auditing a majority of tax returns, while risk management practices remain largely underdeveloped and/or underutilized. There is also plenty of opportunity in many countries to enhance the design and delivery of client-focused taxpayer service programs, and better engage with the private sector and other stakeholders.