Registration is the part of a sex offense case that outlasts everything else, and it is frequently the part nobody explains before a plea. This article covers what registration actually requires, how tier classification is assigned and why it matters more than the sentence, and how residency, employment, and internet restrictions constrain daily life for years or for life. It explains the federal framework and how it interacts with the state systems that do the actual registering, why moving to another state can change classification and duration entirely, and how failure-to-register prosecutions arise from technical omissions rather than from new offenses. Separate parts cover community notification, civil commitment, juvenile registration, and the narrow paths to removal or relief that exist in some states and not others. It also covers what a defense lawyer should tell a client before a plea and what a family member can realistically do to help. Examples run throughout, and the recurring point is that the registration consequence is negotiable at exactly one moment and almost never afterward.