A complete practitioner's treatment of the False Claims Act for relators, defendants, and compliance counsel. Part I sets the statutory architecture and history through the 1986 and 2009 amendments. Part II works each liability provision including the reverse false claim. Part III catalogs the falsity theories from factual falsity through express and implied certification, worthless services, and fraud in the inducement. Parts IV and V cover the two elements that decide modern cases: scienter after United States ex rel. Schutte v. SuperValu, which made the inquiry subjective, and the rigorous materiality standard of Universal Health Services v. Escobar with its continued-payment factor. Part VI covers damages, the per-claim penalty structure, and the Excessive Fines Clause challenge. Part VII walks the qui tam procedure from the sealed complaint and disclosure statement through intervention. Part VIII covers the first-to-file and public disclosure bars, the original source exception, and limitations after Cochise Consultancy. Parts IX and X cover pleading under Rule 9(b), discovery, the government's dismissal power after Polansky, and settlement including corporate integrity agreements. Part XI covers retaliation. Parts XII and XIII cover the health care overlay and the growth areas in contracting, customs, grants, and cybersecurity. Part XIV is defense-side compliance and response, and Part XV covers parallel whistleblower programs and state false claims acts.