Responding to the substantial finance gap for achieving Sustainable Development Goal 6.1 and 6.2, the Water and Sanitation sector has mobilized to launch new blended finance vehicles with increasing frequency. The sustainability and scale-up of financial solutions is intended to support increased access to unserved, marginalized populations. However, without addressing foundational issues in the sector, any finance mechanism, whether public, private or blended, will be a short-term, band-aid solution and the sector will continue the cycle of dependency on external assistance. This paper presents the results of a collaborative effort of Water.org, IRC WASH and the World Bank Water Global Practice. Drawing from the latest research on effective public financial management and based on evidence from the countries where these organizations work, the paper demonstrates that sustainable success in mobilising finance at large scale is dependent on a reasonable level of performance across 10 foundational areas. The paper presents evidence on the 10 foundational areas and discusses why other aspects of finance and governance while necessary are not sufficient. Better coordination amongst all development partners and governments, including a collective commitment to and prioritization of working on these foundational issues, is a necessary first step.