Sustainability implies a comprehensive approach to development that seeks to meet current needs without compromising the ability of future generations to meet their own needs. In this context, water management, as a vital liquid, is a sine qua non condition for achieving sustainability. However, non-revenue water (NRW) is a complex issue as it affects the sustainability of water resources by including both physical losses (leaks in pipes, reservoir leaks, visible leaks, and non-visible leaks) and non-physical losses (illegal connections, metering errors, and inadequate billing), just to mention some implications in the technical, economic, social, and environmental fields. This chapter will explore the non-accounting of water as a global challenge, we will review and discuss its causes, impacts and possible solutions in the topic of NRW within management and sustainability view, to seek for a solution to the problems caused by NRW. The main conclusions are a combination of innovative technologies, effective management practices and community involvement to reduce NRW, which represents a significant challenge for sustainable water management worldwide. The NRW reduction strategies identified were grouped into strategies to reduce apparent losses, real losses, and water losses, the latter involving the combination of apparent losses and real losses. The most frequently adopted strategies are preventing water leaks and controlling water pressure. In addition, rehabilitation of the water distribution network has additional benefits over other real loss reduction strategies, including water and energy savings, increased hydraulic efficiency, and improved reliability.