This publication is one of three policy briefs designed to guide local policymakers in undertaking justice reinvestment, a data-driven strategy to identify the drivers of criminal justice system costs and make more efficient use of resources while maintaining public safety. This brief focuses on the specific justice reinvestment task of tracking costs and anticipated savings to target reinvestment. It provides guidance on how to: conduct a comprehensive assessment of local justice spending; assess cost implications for agencies outside of the criminal justice system; and target reinvestment efforts. Additional resources and a "getting started" worksheet are included in an appendix.