This paper explores the nature, significance and policy implications of spillovers in international corporate taxation—the effects of one country’s rules and practices on others. It complements current initiatives focused on tax avoidance by multinationals, notably the G20-OECD project on Base Erosion and Profit shifting (BEPS). The paper draws on the IMF’s experience on international tax issues with its wide membership, including through technical assistance (TA), and on its previous analytical work, to analyze spillovers and how they might be addressed. In doing so, it goes beyond current initiatives to look at a wide set of possible responses.