Post-grant review (PGR)
Post-grant review is an AIA-created PTAB proceeding allowing a third party to challenge a recently issued patent on virtually any ground of unpatentability during a nine-month window after issuance. Although broader in scope than inter partes review, PGR is rarely used: the short filing window, the heightened pleading standard, and the broader resulting estoppel make it a niche tool.
The rule
A person who is not the patent owner may petition the USPTO to institute a post-grant review of an issued patent. The petition must be filed not later than nine months after the date of issuance (or reissuance, in the case of broadened reissue claims). 35 U.S.C. § 321(c). The petitioner may request cancellation of one or more claims on any ground that could be raised under 35 U.S.C. § 282(b)(2) or (3) — that is, on grounds of subject-matter eligibility, anticipation, obviousness, written description and enablement, or indefiniteness — except that the best-mode requirement is not a basis for cancellation.
The Director may institute PGR only if the petition demonstrates that it is more likely than not that at least one of the challenged claims is unpatentable, or that the petition raises a novel or unsettled legal question that is important to other patents or applications. 35 U.S.C. § 324(a)–(b). That standard is materially higher than the IPR "reasonable likelihood" threshold.
Statutory and regulatory source
The PGR statute occupies 35 U.S.C. §§ 321–329. Section 321 sets the scope and the nine-month window. Section 322 lists petition contents. Section 323 authorizes the patent owner's preliminary response. Section 324 supplies the institution standard. Section 325 governs the relationship to other proceedings, including the § 325(d) discretionary-denial mechanism and the § 325(e) estoppel rule. Section 326 grants rulemaking authority and prescribes the twelve-month decision deadline (extendable by six months). Section 327 addresses settlement. Section 328 governs the final written decision. Section 329 confers the right to appeal.
The Director has implemented these provisions in 37 C.F.R. Part 42, subpart C. Procedural rules common to all PTAB AIA trials — described in PTAB trial procedure — also apply.
PGR is available only against patents whose claims have an effective filing date on or after March 16, 2013 — the effective date of the first-inventor-to-file provisions of the AIA. A pre-AIA patent cannot be the subject of PGR regardless of when issued.
The framework
Petition
The PGR petition mirrors the IPR petition in structure: identification of real parties in interest and related matters, certification of standing, a proposed claim construction (under Phillips as in IPR), and the grounds for cancellation supported by evidence and expert declarations. The petition is limited to 18,750 words — larger than the IPR limit because of the broader available grounds. 37 C.F.R. § 42.24(a)(1)(ii).
Because PGR allows § 101 and § 112 grounds, petitions often include theories that would never arise in IPR. A typical PGR challenges enablement, written description, or eligibility alongside prior-art grounds, and the supporting evidence frequently includes expert testimony on the state of the art and the level of ordinary skill.
Patent owner preliminary response
The patent owner may file a preliminary response within three months of the notice of filing date. 35 U.S.C. § 323. The procedural posture is the same as in IPR: testimonial evidence is permitted, and genuine factual disputes are resolved in the petitioner's favor at the institution stage.
Institution decision
The Director, through PTAB panels, decides institution within three months of the POPR or its deadline. The decision is committed to agency discretion under § 324, and § 324(e) provides that the determination is final and nonappealable. The same general framework that the Supreme Court applied to IPR institution review in Cuozzo Speed Technologies, LLC v. Lee, 579 U.S. 261 (2016), applies to PGR institution.
Trial
Once instituted, the proceeding proceeds as a full PTAB trial with patent owner response, petitioner reply, limited discovery, oral hearing, and a final written decision within twelve months of institution (extendable to eighteen). Following SAS Institute Inc. v. Iancu, 584 U.S. 357 (2018), institution is all-or-nothing on every claim and every ground in the petition; the same rule applies to PGR by parallel statutory structure.
Burden, timing, deadlines
The petitioner bears the burden of proving unpatentability by a preponderance of the evidence. 35 U.S.C. § 326(e). The institution threshold — "more likely than not that at least one of the claims challenged in the petition is unpatentable" — is the highest of the AIA institution standards.
The principal timing rules are:
- The nine-month window. A petition must be filed within nine months of patent issuance. 35 U.S.C. § 321(c). The window is jurisdictional; a petition filed on day 274 is fatally untimely. There is no service-of-complaint trigger as in IPR.
- Mutual exclusivity with IPR. A patent is eligible for IPR only after the nine-month PGR window has closed, or after a PGR has been terminated. 35 U.S.C. § 311(c). The two proceedings cannot run in parallel.
- Civil-action bar. A petitioner who has previously filed a civil action challenging the validity of a claim of the patent may not file a PGR petition. 35 U.S.C. § 325(a)(1). Filing a counterclaim of invalidity does not trigger the bar. § 325(a)(3).
- The twelve-month decision deadline. Section 326(a)(11) requires the final written decision within one year of institution, extendable by six months for good cause.
Interaction with district court litigation
Because of the nine-month window, PGR is most often a vehicle for competitors and standards-watchers monitoring patent issuance, rather than for accused infringers. By the time a complaint is filed and an answer is due, the PGR window has typically closed.
When PGR is available, it imposes a stronger estoppel than IPR. Section 325(e)(1) bars the petitioner, real party in interest, and privies from raising in any subsequent USPTO proceeding any ground that was raised or reasonably could have been raised in the PGR. Section 325(e)(2) imposes a parallel estoppel in district court civil actions and in ITC section 337 investigations. Because PGR's grounds include § 101 and § 112, the post-PGR estoppel reaches a much wider range of validity defenses than the post-IPR estoppel.
Section 325(d) authorizes the Director to deny institution, on a discretionary basis, where the same or substantially the same prior art or arguments previously were presented to the Office. This provision applies in both IPR and PGR but tends to bite most often in PGR, where the grounds frequently overlap with the original prosecution.
Practical notes
- PGR is uncommon. The Board has historically received only a small number of PGR petitions per year, in contrast to the many hundreds of IPR petitions. The combination of the short window, the heightened threshold, and the broad estoppel makes PGR a tool of last resort for most challengers.
- Standards-essential patents are a frequent target. Where a patent issues during a known competitive window — for example, in pharmaceutical or biotech sectors with intense incumbents — the nine-month watch is feasible and PGR sometimes follows.
- Section 101 grounds are unique to PGR. A patentee who survived Alice at examination may face a renewed eligibility challenge in PGR. Once the window closes, eligibility can only be raised in district court or, post-issuance, through ex parte reexamination — and ex parte reexamination is limited to patents and printed publications.
- Section 112 grounds drive expert practice. Enablement and written description challenges in PGR look much like the corresponding district-court attacks but on a compressed schedule and before patent-trained APJs rather than a generalist jury.
- The transitional CBM program has expired. The transitional program for covered business method patents — a PGR-like proceeding for certain financial-services patents under AIA § 18 — sunset on September 16, 2020, and is no longer available.
Open questions
- Whether PGR will see meaningful uptake. Filings have not grown in line with the increasing universe of AIA-eligible patents. Some commentators attribute this to the broader estoppel; others to the nine-month window and the need to monitor issuance proactively.
- The precise contours of § 325(e) estoppel. Because so few PGRs reach final written decision, the case law on PGR estoppel is sparse. The estoppel is statutorily broader than § 315(e) — covering § 101 and § 112 grounds — but its application has not been litigated as extensively. Lower-court decisions interpreting IPR estoppel after California Institute of Technology v. Broadcom Ltd., 25 F.4th 976 (Fed. Cir. 2022), will likely guide PGR estoppel by analogy, but the breadth of grounds creates wider questions about what "reasonably could have been raised" means.
- Discretionary denial under § 325(d). The Director's prior-art-overlap discretion has expanded and contracted across administrations. Its current scope mirrors the unsettled status of the parallel Fintiv framework in IPR.
- Section 101 in administrative adjudication. Whether PTAB panels are well suited to resolve Alice-step-two factual questions on a paper record remains debated, particularly where the same questions in district court would be informed by claim construction, expert testimony, and a developed fact record.
See also
- Inter partes reviewThe narrower-grounds, more-used companion proceeding.
- IPR estoppelThe corresponding § 315(e) estoppel; case law guides PGR estoppel by analogy.
- PTAB trial procedureCommon procedural rules under 37 C.F.R. Part 42.
- Section 101 patent eligibilityAvailable as a PGR ground but not in IPR.
- Written description and enablementSection 112(a) grounds available in PGR.
- DefinitenessSection 112(b) ground also available in PGR.
Last reviewed: 2026