The international humanitarian system provides a global public service but is financed on a voluntary basis. The way official donor funding is mobilised and allocated is unpredictable and haphazard, reducing efficiency and effectiveness. Donors should overcome the collective action problem that is inhibiting change and reach a critical mass of finance delivered through collective mechanisms. This paper outlines the case for - and obstacles against – change. It suggests three ways to make some progress: a multi-year common replenishment model for protracted and predictable crises; rebalancing country-level pooled mechanisms; and aligning core funding to agencies with agreed core functions.