Inter partes review (IPR)
Inter partes review is an adversarial administrative proceeding before the Patent Trial and Appeal Board in which a third party challenges the validity of issued patent claims on grounds of anticipation or obviousness based on patents and printed publications. Created by the America Invents Act, IPR replaced inter partes reexamination and has become the dominant non-Article III forum for patent invalidity disputes.
The rule
A person who is not the owner of a patent may file with the United States Patent and Trademark Office a petition to institute an inter partes review of the patent. The petitioner may request cancellation of one or more claims of the patent on a ground that could be raised under 35 U.S.C. § 102 or § 103, and only on the basis of prior art consisting of patents or printed publications. Other validity defenses — § 101 patent eligibility, § 112 written description and enablement, § 112 definiteness, public use, on-sale activity, derivation — fall outside the IPR jurisdiction and must be raised in district court, before the International Trade Commission, or, where time-eligible, in post-grant review.
The Director of the USPTO may institute IPR only if the petition shows a reasonable likelihood that the petitioner would prevail with respect to at least one challenged claim. 35 U.S.C. § 314(a). When the Board institutes review, it must address every claim and every ground raised in the petition; partial institution is not permitted. SAS Institute Inc. v. Iancu, 584 U.S. 357 (2018).
Statutory and regulatory source
The IPR statute occupies 35 U.S.C. §§ 311–319. Section 311 sets the scope. Section 312 prescribes the petition contents — identification of the real party in interest, the claims challenged, the grounds, and supporting evidence. Section 313 authorizes the patent owner's preliminary response. Section 314 supplies the institution standard and the rule of nonappealability. Section 315 governs the relationship between IPR and other proceedings, including the one-year time bar under § 315(b) and the estoppel rules under § 315(e). Section 316 grants the Director rulemaking authority and sets the twelve-month statutory deadline for the final written decision (extendable by six months for good cause). Section 317 addresses settlement. Section 318 specifies the content of the final written decision and the resulting estoppel certificate. Section 319 provides the right to appeal to the Federal Circuit.
The Director has implemented these provisions in 37 C.F.R. Part 42, with subpart A containing trial practice rules common to all AIA proceedings and subpart B governing inter partes review specifically. The Office Patent Trial Practice Guide, periodically updated, supplies non-binding guidance on Board practice. See also PTAB trial procedure.
The framework
Petition
Any person other than the patent owner may petition. The petitioner must identify all real parties in interest, list any related matters, identify counsel, certify standing (i.e., that the patent is available for IPR and that the petitioner is not estopped), and present the grounds with particularity. The petition is limited to 14,000 words. 37 C.F.R. § 42.24. Expert declarations and documentary evidence accompany the petition. The petitioner must propose a claim construction; since 2018, the Board has applied the Phillips standard used in district court rather than the broadest reasonable interpretation. 37 C.F.R. § 42.100(b).
Patent owner preliminary response
Within three months of the notice of filing date, the patent owner may file a preliminary response (a POPR) explaining why review should not be instituted. 35 U.S.C. § 313; 37 C.F.R. § 42.107. Since 2016, the patent owner may submit testimonial evidence with the POPR, with any genuine factual dispute resolved in the petitioner's favor at the institution stage.
Institution decision
The Director, acting through three-judge panels of administrative patent judges, decides institution within three months of the POPR (or within three months of the deadline if no POPR is filed). The decision is committed to agency discretion under § 314(a) and is statutorily nonappealable. Cuozzo Speed Technologies, LLC v. Lee, 579 U.S. 261 (2016). Cuozzo confirmed that § 314(d)'s no-appeal bar applies to challenges that are "closely tied" to the institution decision, though it left open review of constitutional questions and questions outside the institution determination itself.
Trial
Once instituted, the proceeding becomes a full trial. The patent owner files a response and may move to amend the claims. The petitioner files a reply. Discovery is limited and structured: routine discovery covers cited evidence and inconsistent positions; additional discovery requires a showing under the five-factor test articulated in Garmin International, Inc. v. Cuozzo Speed Technologies LLC, IPR2012-00001 (P.T.A.B. Mar. 5, 2013) (informative). The Board holds an oral hearing, typically about ten months after institution, and issues a final written decision within twelve months — extendable to eighteen for good cause.
Final written decision and Director review
The final written decision addresses the patentability of every instituted claim. Following the Supreme Court's holding in United States v. Arthrex, Inc., 594 U.S. 1 (2021), that administrative patent judges had been exercising principal-officer authority without the requisite Presidential appointment, the remedy is a discretionary review by the Director of any final written decision. The Director's review process — currently structured through the Director Review program — allows the Director to grant, deny, or sua sponte initiate review and either modify or affirm the panel's decision.
Burden, timing, deadlines
The petitioner bears the burden of proving unpatentability by a preponderance of the evidence. 35 U.S.C. § 316(e). This burden never shifts. Dynamic Drinkware, LLC v. National Graphics, Inc., 800 F.3d 1375 (Fed. Cir. 2015), distinguishes the burden of persuasion from the burden of production for prior-art priority disputes.
Two timing rules dominate strategy:
- The § 315(b) one-year bar. An IPR may not be instituted if the petition is filed more than one year after the petitioner, real party in interest, or privy is served with a complaint alleging infringement of the patent. The bar is jurisdictional in operation; the Federal Circuit reviews § 315(b) determinations on the merits notwithstanding § 314(d). Thryv, Inc. v. Click-to-Call Technologies, LP, 590 U.S. 45 (2020), nonetheless held that § 314(d) precludes appellate review of the agency's § 315(b) timeliness ruling itself.
- The twelve-month decision deadline. Section 316(a)(11) requires the final written decision within one year of institution, extendable by six months on a showing of good cause. The deadline runs from institution, not filing.
From a litigant's perspective, the cumulative timeline is roughly six months from petition to institution, then twelve months to final written decision, with appeal to the Federal Circuit thereafter. Total agency-plus-appeal time typically exceeds two years.
Interaction with district court litigation
IPR was designed as a faster, cheaper alternative to district court invalidity litigation. In practice, the two run in parallel. An accused infringer commonly answers the complaint, files an IPR petition within the § 315(b) window, and moves to stay the district court action. Stays are granted with varying frequency depending on case posture and forum: courts in Delaware and the Northern District of California stay more readily than those in the Eastern or Western District of Texas.
The Supreme Court upheld the constitutionality of IPR against an Article III and Seventh Amendment challenge in Oil States Energy Services, LLC v. Greene's Energy Group, LLC, 584 U.S. 325 (2018), holding that patent rights are public rights subject to administrative reconsideration.
Discretionary denial — the Fintiv factors
Under § 314(a), the Director retains discretion to deny institution even when the merits threshold is met. In Apple Inc. v. Fintiv, Inc., IPR2020-00019 (P.T.A.B. Mar. 20, 2020) (precedential), the Board articulated six factors for assessing whether parallel district court litigation counsels denial: (1) whether a stay exists or is likely; (2) the proximity of the trial date to the projected final written decision; (3) investment by the parties and the court in the parallel proceeding; (4) overlap of issues; (5) whether the petitioner and defendant are the same; and (6) other circumstances, including merits strength. The Fintiv framework has been controversial and is the subject of ongoing rulemaking and guidance memoranda from successive USPTO Directors. The current state of Fintiv-based denial is unsettled and changes from administration to administration.
Estoppel
Section 315(e) creates a substantial estoppel against the petitioner, the real party in interest, and privies on grounds raised or that reasonably could have been raised. The estoppel attaches only on a final written decision and applies to subsequent USPTO proceedings, civil actions in district court, and ITC investigations under section 337.
Practical notes
- Word limits matter. The 14,000-word petition cap forces ground selection. Practitioners typically include three to five primary grounds and prioritize the strongest art over comprehensive coverage.
- The POPR has grown important. A persuasive preliminary response can defeat institution, often by exposing a missing claim element or a fatal teaching-away in the petitioner's prior art.
- Claim construction follows Phillips. The 2018 rule change ended the BRI-versus-Phillips arbitrage that previously drove some accused infringers toward IPR even where the patent had been construed in district court. See claim construction.
- Joinder is governed by § 315(c). A timely petitioner may join later petitions to a pending IPR, including in some cases the petitioner's own follow-on petitions, subject to the Board's discretion.
- Appeal lies under § 319. Final written decisions are appealable to the Federal Circuit by any dissatisfied party. Standing on appeal is a recurring issue: a petitioner who is not in litigation must show concrete injury under Article III. See standing.
Open questions
Several aspects of IPR remain in flux:
- The scope of Fintiv discretionary denial. Successive Directors have issued, withdrawn, and revised guidance on when parallel litigation justifies denial. The factors remain in force, but their weight and application shift with USPTO leadership. Whether discretionary denial is properly the subject of formal rulemaking is itself contested.
- The mechanics of Director review. The Arthrex remedy is implemented by Director-issued procedures rather than statute. The shape and reach of Director review — sua sponte initiation, panel rehearing relationships, and the standard of review the Director applies — continues to evolve.
- The §§ 102/103-only limitation in light of AIA prior-art changes. Because IPR is restricted to patents and printed publications, public-use and on-sale challenges remain confined to district court even where the AIA's broader prior-art categories under § 102(a)(1) would otherwise apply. See on-sale bar and public-use bar.
- The boundary of Cuozzo's nonappealability rule. The Supreme Court has narrowed (Thryv) and limited (SAS) the bar in different ways; the precise contours of which institution-related rulings are reviewable continue to generate litigation.
See also
- Post-grant reviewBroader-grounds AIA proceeding available within nine months of issuance.
- IPR estoppelSection 315(e) preclusion against grounds raised or reasonably could have been raised.
- PTAB trial procedurePetition, POPR, institution, trial schedule, oral hearing, final written decision.
- Anticipation under § 102One of the two grounds available in IPR.
- Obviousness under § 103The other available IPR ground; KSR governs.
- Federal Circuit appealsSection 319 appeal route from final written decisions.
Last reviewed: 2026