Total official support for sustainable development (TOSSD) is a new international statistical measure that provides a complete picture of all official resources and private finance mobilised by official interventions in support of sustainable development and the SDGs. It consists of two pillars: cross-border resources to developing countries (pillar I) and support to international public goods and global challenges (pillar II). To test the TOSSD concept and operationalise the reporting, a data survey was carried out in 2019 on 2017 resources. This paper analyses the main lessons learnt from the survey with the objective to help further refine the TOSSD Reporting Instructions and data collection process, and provide evidence to the international community about the usefulness, relevance and feasibility of TOSSD as a measurement framework for the SDG era. TOSSD can respond to developing countries’ needs for information on external financing for sustainable development (pillar I), with estimates showing that between 18% and 26% of the volume of resources captured in the survey relate to additional data captured in TOSSD. TOSSD can fill a key information gap on financing for international public goods (IPGs) that support the achievement SDGs (pillar II). The TOSSD framework is appropriate for various providers of financing for sustainable development, including traditional providers, South-South Co-operation providers and multilateral institutions. To enhance the usefulness and relevance of TOSSD, efforts will need to continue to fill the remaining data gaps and enhance data quality.