IIJA directs Eligible Entities to begin the BEAD challenge process with the FCC National Broadband Map. Eligible Entities are required to identify a version of the FCC map in their BEAD Initial Proposals, and then are permitted to incorporate a more recent version of the FCC map both before and/or after running the BEAD challenge process. The "true-up" with the most recent FCC map is intended to ensure that the Eligible Entity conducts its subgrantee selection process with the most accurate list of BSLs eligible for BEAD funding within its jurisdiction. This guide helps Eligible Entities understand this important process.