In measuring illicit financial flows (IFFs), the United Nations defines IFFs for statistical purposes as “Financial flows that are illicit in origin, transfer or use, that reflect an exchange of value and that cross-country borders.” The United Nations Office on Drugs and Crime (UNODC) and United Nations Conference on Trade and Development (UNCTAD) include aggressive tax avoidance as an IFF source, “as it can be considered detrimental to sustainable development in many countries, even though such activities are generally not illegal.” Without entering the international doctrinal debate as to whether a tax-related IFF must be illegal, this presentation considers from a policy perspective whether there is normative space to occupied by aggressive tax avoidance between tax evasion and a tax-motivated plan that may (or may not) run afoul of an anti-abuse doctrine or otherwise result in an understated tax liability.