Abstract: This 4th edition of Financing and Charges for Wastewater Systems provides an overview of current industry practices that should be considered for financing and establishing rates and charges for wastewater collection and treatment systems. In addition, this Manual of Practice reflects and is responsive to changes in the industry over the last decade that have occasioned a heightened awareness about wastewater utility financial management and the equitable distribution of cost responsibilities across customer groups or classes. These changes, including tightening environmental regulation and replacement of aging infrastructure, have resulted in a pronounced increase in the cost of wastewater services. At the same time, the portion of costs paid through federal and state assistance programs have declined, challenging the affordability of this vital service. In this context, guidance on wastewater rate-setting practices, and particularly the distribution of costs across user groups, is of critical importance.