IPR vs. PGR: Inter Partes Review and Post-Grant Review Compared

Sources: 35 U.S.C. § 311, § 314, § 315, § 316, § 321, § 324, § 325, § 326; 37 C.F.R. § 42.15, § 42.24; AIA § 6(f)(2)(A); Director Institution memorandum (Oct. 17, 2025). Each row is explained below.

PGR must be filed no later than nine months after the patent issues, or after a reissue patent issues (35 U.S.C. § 321(c)). It is also limited to patents under the first-inventor-to-file system: the America Invents Act applies chapter 32 "only to patents described in section 3(n)(1)" of the Act, which covers patents from applications that contain, or at any time contained, a claim with an effective filing date on or after March 16, 2013, or a specific reference under 35 U.S.C. § 120, 121 or 365(c) to a patent or application that did. A reissue claim identical to or narrower than an original claim cannot be challenged in PGR once the original patent’s nine-month window has closed (§ 325(f)).

IPR may be filed after the later of nine months from grant or the end of an instituted PGR (§ 311(c)). For a patent that is not a first-inventor-to-file patent, the USPTO’s rule lets an IPR be filed from the date of grant (37 C.F.R. § 42.102(a)(2)), since no PGR window exists for it. An IPR can be filed at any point after that, for the rest of the patent’s life, with two important limits:

• The one-year bar. An IPR may not be instituted if the petition is filed more than one year after the petitioner, its real party in interest or its privy was served with a complaint alleging infringement of the patent (§ 315(b)). Joinder requests are exempt from the bar. The Supreme Court held in Thryv v. Click-to-Call (2020) that the Board’s application of this bar cannot be appealed.
• Your own declaratory-judgment suit. Neither proceeding may be instituted if, before the petition, the petitioner or real party in interest filed a civil action challenging the validity of a claim of the patent (§§ 315(a)(1), 325(a)(1)). A counterclaim of invalidity does not count (§§ 315(a)(3), 325(a)(3)).

PGR has no one-year bar of its own; its deadline runs from grant or reissue instead. But if the patent owner sues within three months of grant, a court may not refuse to consider a preliminary injunction motion because a PGR was filed or instituted (§ 325(b)).

Sources: 35 U.S.C. § 311(c), § 315(a)-(b), § 321(c), § 325(a), (b), (f); AIA § 6(f)(2)(A) and § 3(n)(1); MPEP chapter 2100 (§ 2159) on the March 16, 2013 line; 37 C.F.R. § 42.102, § 42.202; Thryv, Inc. v. Click-to-Call Technologies, LP, 590 U.S. 45 (2020).

This is the largest practical difference. An IPR petitioner may ask to cancel claims "only on a ground that could be raised under section 102 or 103 and only on the basis of prior art consisting of patents or printed publications" (§ 311(b)). Prior sales, public uses and physical products are outside an IPR, and so are eligibility (§ 101) and the written description, enablement and definiteness requirements of § 112. For IPR petitions filed on or after September 1, 2025, the USPTO enforces (under a July 31, 2025 memorandum) the rule that an IPR petition must show where each claim element is found in the patents or printed publications relied on; applicant-admitted prior art, expert testimony and common sense may not supply a missing limitation, though they may still show motivation to combine or the knowledge of a skilled artisan.

A PGR petitioner may raise any ground that could be raised under § 282(b)(2) or (3) (§ 321(b)): the conditions for patentability in Part II of the Patent Act, such as eligibility (§ 101), novelty (§ 102) and non-obviousness (§ 103), on any kind of prior art, and failure to meet § 112 (except the best-mode requirement) or § 251. Of the PTAB trials open to new petitions, PGR is the only one that can hear an eligibility or § 112 attack on issued claims, or invalidity based on a prior sale or public use.

Sources: 35 U.S.C. § 311(b), § 321(b), § 282(b); 37 C.F.R. § 42.104(b), § 42.204(b); USPTO memorandum on § 42.104(b)(4) and general knowledge (July 31, 2025).

Neither trial starts on filing. The patent owner may file a preliminary response within three months of the notice according the petition a filing date (37 C.F.R. §§ 42.107(b), 42.207(b)), and the institution decision is due within three months after that response, or after its due date if none is filed (§§ 314(b), 324(c)).

• IPR: institution requires "a reasonable likelihood that the petitioner would prevail with respect to at least 1 of the claims challenged" (§ 314(a)). The USPTO calls it "a somewhat flexible standard that allows the Board room to exercise judgment."
• PGR: institution requires that the petition, if unrebutted, "would demonstrate that it is more likely than not that at least 1 of the claims challenged in the petition is unpatentable" (§ 324(a)), which the USPTO reads as "greater than 50% chance of prevailing." Alternatively, the petition may raise "a novel or unsettled legal question that is important to other patents or patent applications" (§ 324(b)).

Institution is all or nothing: if a trial is instituted, it covers every challenged claim and every ground in the petition (SAS Institute v. Iancu (2018); 37 C.F.R. §§ 42.108(a), 42.208(a)). And the decision whether to institute is "final and nonappealable" (§§ 314(d), 324(e)); the Supreme Court applied that bar in Cuozzo Speed Technologies v. Lee (2016) to questions closely tied to the institution decision, while SAS confirms that courts can still ensure the Office stays within its statutory bounds.

Sources: 35 U.S.C. § 314, § 324; 37 C.F.R. § 42.107, § 42.108, § 42.207, § 42.208; PTAB Consolidated Trial Practice Guide (Dec. 2025); SAS Institute Inc. v. Iancu, 584 U.S. 357 (2018); Cuozzo Speed Technologies, LLC v. Lee, 579 U.S. 261 (2016).

The statutes have not changed, but the process for deciding institution has, through Director memoranda rather than rules. As of October 15, 2026, this is what applies to both IPR and PGR:

1. Separate briefing on discretion (since March 26, 2025). The patent owner may file a brief asking for discretionary denial within two months of the notice of filing date accorded; the petitioner may file an opposition within three months of that notice. The parties may address prior adjudications of the claims, changes in the law, the strength of the challenge, reliance on expert testimony, "settled expectations of the parties, such as the length of time the claims have been in force," compelling economic, public health or national security interests, and anything else bearing on discretion, alongside the Board’s Fintiv, General Plastic and Advanced Bionics precedents.
2. The Director decides institution (since October 20, 2025). "The Director, in consultation with at least three PTAB judges, will determine whether to institute trials in all IPR and PGR proceedings," weighing discretionary considerations, the merits and non-discretionary issues; petitions already referred to a panel before October 20, 2025 stayed with it. Routine decisions are summary notices granting or denying institution; the Director may write a decision on novel or important issues or refer one to PTAB judges. An instituted trial goes to a three-judge panel.
3. Search disclosures (since November 17, 2025). A petitioner may file a voluntary Search Disclosure Declaration explaining how it found its prior art; the USPTO treats it as a "non-exclusive, non-dispositive favorable discretionary factor supporting institution."
4. U.S. manufacturing and small businesses (since March 11, 2026). The Director considers whether products accused in a parallel proceeding are made in the United States, whether the patent owner’s competing products are, and whether the petitioner is a small business sued on the patent.

A proposed rule is pending, not in force. On October 17, 2025 the USPTO proposed rules (RIN 0651-AD89) that would generally bar instituting or maintaining an IPR: unless the petitioner stipulates not to raise § 102 or § 103 invalidity in any other proceeding; where a challenged claim, or an independent claim it depends on, was upheld in specified earlier rulings (a district court trial or summary judgment, an ITC determination, a final written decision, or an ex parte reexamination requested by someone other than the patent owner or its real party in interest or privy); or where a district court trial on § 102 or § 103 challenges, an ITC determination on those grounds, or another final written decision on such a claim is more likely than not to come before the IPR’s deadline. A panel could refer extraordinary cases to the Director, who could institute personally. The proposal amends only the IPR rule (§ 42.108), not PGR. No final rule had been published in the Federal Register as of October 15, 2026; check before relying on this page.

Sources: Interim Processes for PTAB Workload Management (Mar. 26, 2025); Interim Director Discretionary Process (USPTO page); Director Institution of AIA Trial Proceedings (Oct. 17, 2025); Voluntary Search Disclosure Declarations (Nov. 17, 2025); U.S. Manufacturing and Small Business Use of AIA Proceedings (Mar. 11, 2026); PTAB rules, guidance and memoranda list; Revision to Rules of Practice Before the PTAB, 90 FR 48335 (proposed Oct. 17, 2025); Federal Register documents for RIN 0651-AD89.

Once instituted, the two trials run on nearly the same rules (37 C.F.R. Part 42, subpart A). If a trial is instituted and not dismissed, the PTAB must issue a final written decision within one year of institution, extendable by up to six months for good cause and adjustable for joinder (§§ 316(a)(11), 326(a)(11)). The petitioner must prove unpatentability "by a preponderance of the evidence" (§§ 316(e), 326(e)). Claims are construed under the same standard a court uses in an infringement suit (37 C.F.R. §§ 42.100(b), 42.200(b)). Under a July 29, 2025 memorandum, in trials whose oral hearing had not yet occurred, Board panels address every ground raised in the petition in the final written decision, absent extraordinary circumstances.

• Discovery. In IPR it is limited to depositions of witnesses who submit declarations and "what is otherwise necessary in the interest of justice" (§ 316(a)(5)). In PGR it is limited to "evidence directly related to factual assertions advanced by either party" (§ 326(a)(5)).
• Amendment. In both, the patent owner may file one motion to amend to cancel claims or propose a reasonable number of substitute claims, which may not enlarge the claims or add new matter (§§ 316(d), 326(d)). In PGR, more motions may be allowed "upon the request of the patent owner for good cause shown" (§ 326(d)(2)).
• Review and appeal. A party may ask the Director to review the institution decision or the final written decision (37 C.F.R. § 42.75). Director Review traces to United States v. Arthrex (2021), in which the controlling opinion on remedy concluded that the Director may review final PTAB decisions. A party dissatisfied with the final written decision may appeal to the Federal Circuit (§§ 319, 329), but must show Article III standing to do so (Consumer Watchdog v. WARF, Fed. Cir. 2014).

Sources: 35 U.S.C. § 316, § 326, § 319; 37 C.F.R. § 42.100, § 42.200, § 42.75; Final Written Decision Procedures memorandum (July 29, 2025); United States v. Arthrex, Inc., 594 U.S. 1 (2021); Consumer Watchdog v. Wisconsin Alumni Research Foundation, 753 F.3d 1258 (Fed. Cir. 2014).

Both fees are paid when the petition is filed: a request fee and a post-institution fee, for up to 20 challenged claims, plus a charge for each claim beyond 20. The fee schedule lists the same amounts for small and micro entities, so there is no small-business discount for either trial.

These are government fees only. Our official sources do not quantify attorney and expert costs, so we do not estimate them here.

Sources: 37 C.F.R. § 42.15 (eCFR, current through Oct. 13, 2026); USPTO fee schedule, PTAB fees.

If either trial ends in a final written decision on a claim, the petitioner, its real party in interest and its privies may not (1) request or maintain a USPTO proceeding on that claim, or (2) argue in a civil action or at the ITC that the claim is invalid, "on any ground that the petitioner raised or reasonably could have raised" during the review (§§ 315(e), 325(e)).

• Same words, different reach. An IPR could only have raised § 102 and § 103 grounds on patents and printed publications, so that is the outer edge of IPR estoppel. In Ingenico v. IOENGINE (Fed. Cir. 2025) the court held that IPR estoppel does not bar arguing in court that the invention was known or used by others, on sale or in public use, grounds an IPR cannot hear, even where the same patents or printed publications serve as evidence. A PGR could have raised eligibility, § 112 and on-sale or public-use grounds too, so the set of grounds that "reasonably could have" been raised is wider.
• Grounds you left out still count. In California Institute of Technology v. Broadcom (Fed. Cir. 2022) the court held that estoppel applies "not just to claims and grounds asserted in the petition and instituted for consideration by the Board, but to all claims and grounds not in the IPR but which reasonably could have been included in the petition." Under § 315(e) it still attaches only to a claim that reached a final written decision.
• Settlement can prevent estoppel. If the trial is terminated by joint request on settlement before the Office decides the merits, no estoppel attaches to that petitioner (§§ 317(a), 327(a)).

Sources: 35 U.S.C. § 315(e), § 325(e), § 317; 37 C.F.R. § 42.73(d); California Institute of Technology v. Broadcom Ltd., 25 F.4th 976 (Fed. Cir. 2022); Ingenico Inc. v. IOENGINE, LLC, No. 2023-1367 (Fed. Cir. May 7, 2025).

• PGR fits when a competitor’s first-inventor-to-file patent issued less than nine months ago and your best arguments are eligibility, § 112 or a prior sale or public use, or when you want to challenge before any lawsuit exists. Plan for the differently worded institution standard, the higher fees and the wider estoppel. In our view, watching newly issued patents in your field is the practical way to catch the window.
• IPR fits when the window has closed, or the patent predates the first-inventor-to-file system, and your case rests on prior patents and publications. If you have been sued, the one-year clock from service governs your timing; file early enough to answer a discretionary-denial brief on the merits and on the parallel case.
• For both, expect a discretionary-denial fight under the Director’s current process, especially with parallel litigation or long-standing claims, and remember that a denial cannot be appealed. Our PTAB dashboard shows institution outcomes, and the discretionary denial decisions and Director Review decisions we summarize show how the factors are being applied.

If the trial looks unavailable, compare IPR with ex parte reexamination, which has no one-year bar, and the PTAB with district court for invalidity in litigation. Everything on post-grant practice is on our PTAB hub.

Sources: 35 U.S.C. § 315(b), § 321, § 324(a), § 325(e); Director Institution of AIA Trial Proceedings (Oct. 17, 2025); 35 U.S.C. § 314(d). Which route fits is our own view, not legal advice.