Global fragmented production and associated trade in intermediate products has changed how economists study globalization and how new public policies are shaped. This creates a need for understanding cross-border flows of disembodied knowledge, often associated with intellectual property (IP). However, data on these international IP-related knowledge flows, specifically, cross-border payments for use of IP, are distorted. The chapter shows how tax planning by multinational enterprises has seriously distorted the measurement of cross-border IP flows, with tax-induced mismeasurement potentially exceeding 35% of global Charges for Use of Intellectual Property (CUIP), and more for individual countries, particularly high-tax-rate countries. This chapter describes the trend of increased cross-border trade in ideas, assessing the main data sources and distortions to these flows. The chapter analyses the tax effects on cross border IP measures and the magnitudes and trends in the tax distortions. It concludes with some possible avenues for reducing mismeasurement distortions, directed at national statisticians, national tax administrations, policymakers and analysts, and academics.