An estimated two billion working-age adults have no account at a formal financial institution. That severely limits their economic prospects. Financial exclusion is closely tied to poverty and economic vulnerability. An estimated 50-60% of the world’s population works in the informal economy, where job security and bargaining power are severely limited. The share of informality is considerably higher for poorer countries and lower-income groups. These figures mirror those for financial exclusion: some 50% of all working-age adults are excluded from formal financial services. For the lowest income quintile, that figure rises to 77%. While those who are financially excluded often don’t have much money, they do have to save, borrow, and carry out day-to-day financial transactions. If they can’t use official bank services like savings accounts, debit cards, insurance, or credit, they have to rely on informal systems. So they borrow from family, friends, pawnbrokers, or money lenders; they save by stashing money in their homes; and they pay in cash. Such informal methods of money management are often insufficient, risky, expensive, and unpredictable, whereas access to formal financial services improves individual and household welfare and helps to reduce poverty. One long-term impact study found that M-PESA, a mobile money service in Kenya, has lifted nearly 200,000 households out of poverty since its launch in 2007. But the benefits of financial inclusion extend further. In fact, it is an enabler of eight of the 17 Sustainable Development Goals, from promoting economic growth and jobs to achieving gender equality. According to the McKinsey Global Institute, digital finance alone could spur inclusive growth that adds $3.7 trillion to the GDP of emerging economies within a decade. Among those who benefited most from M-PESA have been poor women and members of the households they head. Financial inclusion also creates more stable financial systems. When people put their savings into banks, those resources become available for other growth-enhancing activities. And when people operate more broadly within the formal economy, government revenue rises, supporting policies that advance other development priorities. The SDGs’ recognition of the role of financial inclusion highlights growing awareness of its importance among policymakers and the development community. But, for the huge number of people still excluded from the formal financial sector, awareness isn’t enough.