Strengthening Domestic Resource Mobilization: Moving from Theory to Practice in Low- and Middle-Income Countries analyzes the present status of government revenues and presents policy and administrative options relevant to these settings. The authors call for a joint consideration of tax and expenditure policy to enhance the likelihood of success in ensuring revenue sufficiency for sustained economic and social development. Increased domestic revenues can only lead to improved development outcomes if they are translated into productive and beneficial public expenditures. Public spending plays a key role in the economic growth and development in low- and middle-income countries. When revenue and expenditure reforms are embedded in broader public financial management reforms, Domestic resource mobilization becomes a development tool to support sustainable, inclusive development. The role of subnational governments in revenue mobilization and service delivery expenditure must also be included in the revenue mobilization agenda. The authors discuss the challenges of funding the Sustainable Development Goals, present revenue trends, explore reasons for continued revenue gaps and approaches to revenue augmentation, and detail issues in tax structure reform and initiatives to modernize tax administration. They provide a broad landscape of practical examples, drawing from lessons learned in World Bank operations across Global Practices in recent decades. The authors intend this publication to be a starting point for a more comprehensive research agenda rather than a complete inventory in itself.