This chapter turns to the structure of the tax compliance system and how it attempts to address high-end noncompliance. It begins by situating the tax compliance rules within the broader tax system. The discussion considers what they share with all tax rules and what sets them apart. The following sections begin a more detailed dive into the structure of the tax compliance system. After addressing what motivates taxpayers to comply with the tax law, the discussion considers the main components of the tax compliance system, and how these components leverage taxpayer motivations to improve compliance. With this important context on the tax compliance system established, the discussion then returns to the challenges of high-end noncompliance. The final part of this chapter describes the two most prominent approaches in current law and reform proposals. The first general approach is to increase funding of the Internal Revenue Service so it can more effectively deter noncompliance and recover unpaid taxes. The second general approach is what this book terms “activity-based” rules, targeting the specific taxpayer activities that can either indicate or enable tax noncompliance.