The Sustainable Development Goals (SDGs) call for major societal transformations that will require significant fiscal outlays as well as private investments. The fiscal outlays cover public investments, the public provision of social services, and social protection for vulnerable populations. The key message of this paper, building on recent reports by the IMF and SDSN (IMF, 2019b; SDSN, 2018) is that the governments of Low-Income Developing Countries (LIDCs) will require a substantial increase in fiscal (budget) revenues, far beyond what they can achieve by their own fiscal reforms. For this reason, SDG financing will require substantial international cooperation to enable the LIDCs to finance their SDG fiscal outlays. One important source of increased revenues should be the globally coordinated taxation of ultra-high-net worth assets. Today’s ultra-rich should help to pay for the survival and basic needs of the world’s poorest people.