How can we scientifically analyze behaviors we cannot see? Tax evaders usually hide their actions from outside observers, like researchers and governments. We review the creative strategies scholars and policymakers use to overcome this difficulty. How and why do people evade? How does the information tax enforcers observe shape how they combat evasion? How does tax evasion contribute to economic inequality? To answer these questions, students will develop and apply core skills in social science: understanding economic and legal institutions, interpreting evidence from statistical analyses and case studies, and integrating evidence with abstract theoretical ideas to craft and criticize arguments.