Inter Partes Review (IPR): How the PTAB Trial Works

IPR is set out in chapter 31 of the Patent Act (35 U.S.C. §§ 311-319), in the form enacted by § 6(a) of the America Invents Act (Pub. L. 112-29, Sept. 16, 2011). "A person who is not the owner of a patent may file with the Office a petition to institute an inter partes review of the patent" (§ 311(a)). It is adversarial: the petitioner and the patent owner exchange briefs and evidence, cross-examine each other’s declarants, and may argue at an oral hearing, much as in litigation, but before a three-member panel of the PTAB rather than a court.

Sources: 35 U.S.C. § 311, § 312(a)(2), § 314(a), § 315(b), (e), § 316(a)(11), (e), § 319; 37 C.F.R. § 42.15; Director Institution of AIA Trial Proceedings (Oct. 17, 2025). Each row is explained below.

The petition must identify "all real parties in interest" (§ 312(a)(2)); an IPR cannot be filed anonymously. It may be filed only after the later of nine months from grant (for a patent described in § 3(n)(1) of the America Invents Act, explained in IPR vs. PGR) or the date of grant (for other patents), and, if a post-grant review was instituted, after that review ends (§ 311(c); 37 C.F.R. § 42.102(a)). Three bars then apply:

• The one-year bar. An IPR "may not be instituted if the petition requesting the proceeding is filed more than 1 year after the date on which the petitioner, real party in interest, or privy of the petitioner is served with a complaint alleging infringement of the patent" (§ 315(b)). The bar does not apply to a request for joinder, which must be filed no later than one month after institution of the IPR to be joined (37 C.F.R. § 42.122(b)). In Thryv v. Click-to-Call (2020) the Supreme Court held that the Board’s application of the bar cannot be appealed.
• Your own validity suit. No IPR 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; a counterclaim of invalidity does not count (§ 315(a)(1), (3)).
• Estoppel. A petitioner, real party in interest or privy that is estopped from challenging the claims on the grounds identified (for example, by an earlier final written decision) may not petition (37 C.F.R. § 42.101(c)), and every petition must certify that the petitioner is not barred or estopped (§ 42.104(a)).

Sources: 35 U.S.C. § 311(c), § 312(a), § 315(a)-(c); 37 C.F.R. § 42.101, § 42.102, § 42.104(a), § 42.122; Thryv, Inc. v. Click-to-Call Technologies, LP, 590 U.S. 45 (2020).

A 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)). Eligibility (§ 101), the § 112 requirements, and prior sales, public uses and products are outside IPR; within nine months of grant, some of those can be raised in post-grant review (see IPR vs. PGR).

The petition must identify each claim, the statutory ground and the patents or printed publications for each ground, how the claim should be construed, and "where each element of the claim is found in the prior art patents or printed publications relied upon" (37 C.F.R. § 42.104(b)). For petitions filed on or after September 1, 2025, a July 31, 2025 memorandum enforces that last requirement: applicant admitted prior art, expert testimony, common sense and other "general knowledge" may not supply a missing claim limitation, though they may still support a motivation to combine or show what a skilled artisan knew. A petition is limited to 14,000 words (§ 42.24(a)(1)(i)).

Sources: 35 U.S.C. § 311(b); 37 C.F.R. § 42.104(b), § 42.24; Enforcement and Non-waiver of 37 C.F.R. § 42.104(b)(4) (July 31, 2025).

Filing a petition does not start a trial. The Director "may not authorize an inter partes review to be instituted unless" the petition and any preliminary response show "a reasonable likelihood that the petitioner would prevail with respect to at least 1 of the claims challenged" (§ 314(a)). The Trial Practice Guide calls this "a somewhat flexible standard that allows the Board room to exercise judgment." 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)), and the institution decision is due within three months after that response is filed or due (§ 314(b)). If review is instituted, it covers all challenged claims and all grounds (§ 42.108(a)). The decision whether to institute is "final and nonappealable" (§ 314(d)).

Meeting the threshold does not guarantee a trial. As of October 19, 2026, institution works this way under the Director’s memoranda, which changed the process without a new rule:

1. Separate discretionary briefing (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, and the petitioner may oppose within three months of that notice; where the patent owner’s brief was due on or after September 1, 2025, each side’s brief is limited to 20 pages. The parties may address earlier decisions on the claims, changes in the law, the strength of the challenge, the petition’s 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 (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. Routine decisions are summary notices; the Director may write on novel or important issues or refer a decision needing detailed treatment to PTAB judges. An instituted trial goes to a three-member panel.
3. Search disclosures (since November 17, 2025). A petitioner may file a voluntary Search Disclosure Declaration describing how it found its art, which the Director treats 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, and the patent owner’s competing products, are made in the United States, and whether the petitioner is a small business sued on the patent.

Still only a proposal. On October 17, 2025 the USPTO proposed rules (RIN 0651-AD89) that would, among other things, bar institution unless the petitioner stipulates not to raise § 102 or § 103 invalidity in any other proceeding, and where a challenged claim was already upheld in specified earlier rulings or a parallel trial is likely to come first. Our search of the Federal Register on October 18, 2026 found only the two proposed-rule documents and no final rule, and the PTAB’s guidance page lists no memorandum newer than March 11, 2026.

Sources: 35 U.S.C. § 314; 37 C.F.R. § 42.107, § 42.108; PTAB Consolidated Trial Practice Guide; Interim Processes for PTAB Workload Management (Mar. 26, 2025); Interim Director Discretionary Process; 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; Revision to Rules of Practice Before the PTAB, 90 FR 48335 (proposed Oct. 17, 2025).

In practice, that allows about 18 months from the filing-date notice to a final written decision. At trial the petitioner must prove unpatentability "by a preponderance of the evidence" (§ 316(e)). Claims are construed under the same standard a court uses in an infringement suit, and a prior court or ITC construction timely made of record will be considered (37 C.F.R. § 42.100(b)). Discovery is limited to depositions of witnesses who submit declarations and "what is otherwise necessary in the interest of justice" (§ 316(a)(5)). The patent owner may file one motion to amend, cancelling claims or proposing "a reasonable number of substitute claims" that do not enlarge the claims or add new matter (§ 316(d)).

Sources: 35 U.S.C. § 314(b), § 315(b), § 316; 37 C.F.R. § 42.24, § 42.70, § 42.100, § 42.107, § 42.120, § 42.121; Interim Director Discretionary Process; PTAB Consolidated Trial Practice Guide.

Both fees are paid when the petition is filed. The fee schedule lists the same amounts for small and micro entities, so there is no discount.

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

Sources: 37 C.F.R. § 42.15; USPTO fee schedule (updated Aug. 14, 2026).

When an IPR results in a final written decision on a claim, the petitioner, its real party in interest and its privies may not request or maintain a USPTO proceeding on that claim, or assert 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 that inter partes review" (§ 315(e)).

• Grounds left out still count. In California Institute of Technology v. Broadcom (2022), the Federal Circuit 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."
• Grounds an IPR cannot hear survive. In Ingenico v. IOENGINE (2025), the court held that IPR estoppel "does not preclude a petitioner from asserting the same prior art raised in an IPR in district court"; a petitioner may rely on the same patents and publications as evidence of a ground an IPR could not hear, such as prior knowledge or use, sale or public use.
• No final decision, no estoppel. Estoppel attaches only to a claim that reaches a final written decision; if the review is terminated on settlement, no estoppel attaches to that petitioner (§ 317(a)).

Sources: 35 U.S.C. § 315(e), § 317(a); 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).

• Within the USPTO. A party may request rehearing by the Board or, instead, one request for Director Review of a decision on institution or a final written decision (37 C.F.R. §§ 42.71(d), 42.75(c)), within 30 days of a final decision or a decision not to institute and 14 days of a decision to institute; the Director Review fee is $452.
• To the Federal Circuit. "A party dissatisfied with the final written decision" may appeal under §§ 141-144 (§ 319), and only to the Federal Circuit (§ 141(c); 28 U.S.C. § 1295(a)(4)(A)). The notice of appeal is filed with the Director no later than 63 days after the final Board decision, and a timely rehearing request resets that time (37 C.F.R. § 90.3). The Director may intervene (§ 143).
• Standing. A losing petitioner must show an injury in fact to appeal; in Consumer Watchdog v. WARF (2014) the Federal Circuit dismissed an appeal by a challenger without one.

Once the time for appeal has expired or any appeal has ended, the Director issues a certificate cancelling the claims found unpatentable, confirming those found patentable and adding any amended or new claims; those new claims carry intervening rights for anyone who made, purchased or used in the United States, or imported, what they cover, or made substantial preparation to, before the certificate (§ 318(b)-(c)). Appeals are covered in our guide to Federal Circuit appeals.

Sources: 37 C.F.R. § 42.71, § 42.75, § 42.15(f), § 90.3; 35 U.S.C. § 318, § 319, § 141(c), § 143; 28 U.S.C. § 1295(a)(4)(A); Consumer Watchdog v. Wisconsin Alumni Research Foundation, 753 F.3d 1258 (Fed. Cir. 2014).

• Running out the one-year clock. The bar runs from service of the complaint on you, your real party in interest or your privy, not from when you decide to fight. In our view, filing late in the year also gives the parallel case time to advance before the Director weighs discretion.
• Filing a declaratory-judgment action first. A validity suit filed before the petition bars the IPR; a counterclaim does not (§ 315(a)).
• Leaning on expert testimony to fill a gap. Since September 1, 2025, every claim element must be found in the patents or printed publications relied on (§ 42.104(b)(4)).
• Ignoring discretion. Answer the discretionary-denial brief on time; the parallel litigation, how long the claims have been in force and earlier rulings on the same claims all weigh in the Director’s decision, which cannot be appealed.
• Holding back art for court. Grounds you reasonably could have raised are estopped after a final written decision, whether or not you raised them.

Sources: 35 U.S.C. § 314(d), § 315; 37 C.F.R. § 42.104; Interim Processes for PTAB Workload Management (Mar. 26, 2025); Enforcement and Non-waiver of 37 C.F.R. § 42.104(b)(4) (July 31, 2025); Caltech v. Broadcom (Fed. Cir. 2022). Follow the latest discretionary denial decisions, Director Review decisions and institution statistics on the PTAB dashboard; everything on post-grant practice is on our PTAB hub.