Considerable finance is needed to drive the transition to a green, inclusive economy. A “clean trillion” of additional investment is needed annually up to 2030 to enable new infrastructure to be made green. Private capital is needed to finance this transition, complemented by public expenditure, but is currently being channeled into an unsustainable economy. Traded financial capital globally amounts to US$225 trillion, but little of this is being used to power the transition to a green and inclusive economy. Aligning the financial system to enable the long-term health of the real economy may require changes to its architecture, the ‘rules’ governing how it operates. UNEP has established the Inquiry into the Design of a Sustainable Financial System to address this high-potential policy arena. Building on UNEP’s green economy initiative and two decades of work of the UNEP Finance Initiative, the Inquiry is being guided by a high-level Advisory Panel, and involves wide-reaching engagement and research at the national and international levels.