Inter partes review (IPR) lets someone other than the patent owner ask the Patent Office to review issued claims. Under 35 U.S.C. 311(b), the challenge is limited to anticipation or obviousness based on patents or printed publications. It is a patentability proceeding, not a trial over infringement or damages.
What determines whether review starts?
Section 314(a) requires a reasonable likelihood that the petitioner would prevail on at least one challenged claim. Meeting that threshold does not guarantee institution. The USPTO also considers discretionary grounds for denial, including parallel proceedings.
The October 17, 2025 memorandum, effective October 20, places institution decisions with the Director after consultation with at least three PTAB judges. It preserves separate discretionary briefing. An instituted trial proceeds before a three-member panel. The March 11, 2026 memorandum adds specified U.S. manufacturing and small-business considerations.
What deadlines and estoppel matter?
Under section 315(b), service of an infringement complaint generally starts a one-year filing limit for the petitioner, its real party in interest, or its privy; the statute contains a joinder exception. Section 315(a) separately addresses earlier civil actions challenging validity. Counsel should check both provisions before filing.
Section 315(e) ties estoppel to a final written decision concerning a claim, not simply to losing. It limits the petitioner, its real party in interest, and its privy from pursuing grounds raised or reasonably available in that IPR in later Office proceedings, district court, or the ITC, as the statute specifies.
How is post-grant review different?
Post-grant review (PGR) permits broader invalidity grounds for eligible patents and generally requires a petition within nine months after grant or reissue. Section 324 allows institution based on a more-likely-than-not showing of unpatentability or a qualifying novel or unsettled legal question. Patent eligibility, deadlines, and the proposed grounds require separate review.
How should I evaluate an IPR?
Compare the available prior art, filing deadlines, institution risks, and potential estoppel. A general institution-rate statistic cannot tell you whether a particular petition will proceed. The related PTAB, reexamination, and stay guides explain those separate decisions.