A federal trademark registration behaves less like a deed and more like a lease that the government cancels the day you stop paying rent in the currency it accepts, which is proof of use. This guide maps every post-registration obligation the Lanham Act imposes: the Section 8 declaration of continued use at years five-to-six and every renewal, the Section 9 renewal each decade, the Section 71 affidavit for Madrid-based registrations, and the optional Section 15 declaration of incontestability. It works through specimens, the USPTO proof-of-use audit program, Trademark Modernization Act expungement and reexamination, the 2025 fee restructuring, grace periods, and the automatic-cancellation trap that swallows careless docketing. It then turns to the substantive ways a perfectly maintained registration can still die: genericide, abandonment through nonuse, and naked licensing. It closes with corrections, assignment recording, post-registration office actions, a docketing-and-recordkeeping system, worked hypotheticals, an FAQ, and cross-references to related UpLaw resources.