Since 2015, the World Health Organization and the World Bank have been reporting progress on reducing financial hardship at the global level using two main indicators: i) the incidence of catastrophic health spending, defined as the population with large OOP spending in relation to household consumption or income (Sustainable Development Goal (SDG) indicator 3.8.2 with ‘large’ defined using two thresholds 10% and 25%); and ii) recognizing that even lower thresholds of OOP health spending in consumption or income can lead to financial hardship, the proportion of the population impoverished by OOP health spending (1). This report goes one step further, to include a focus on the poor spending any amount on health OOP. Those payments matter: they represent a major challenge to “End poverty in all its forms everywhere” (SDG 1) arising from OOP health spending by the poorest. Tracking all OOP health spending is critical to monitoring financial hardship across the whole population, in line with the pledge to leave no one behind that is at the heart of the SDGs.