To support policy efforts and countries reporting towards Agenda 2030, UNCTAD and UNODC, co-custodians of SDG Indicator 16.4.1 “total value of inward and outward illicit financial flows” have pilot tested methodological guidelines to measure and estimate tax and commercial IFFs as well as crime related IFFs in 22 countries, with the collaboration of UN Regional Commissions. The side event, co-organized by UNCTAD, ECA and ESCAP will showcase success stories in the measurement of IFFs and share key lessons that are critical to regularizing the production of data on SDG 16.4.1 and how it can support policy actions. Conceptual and methodological work, both in measurement and policy formulation, will be presented by the UN, and the successes and lessons will be presented by two pioneering country experts.