Inter partes review (IPR)

1. PetitionA person who is not the owner of the patent files a petition with the USPTO². It must be accompanied by the fee, identify all real parties in interest, and identify each challenged claim, the grounds and the supporting evidence, including copies of the patents and printed publications relied on⁶. For first-inventor-to-file patents it may be filed after the later of 9 months after grant or the end of an instituted post-grant review^1,2.
2. Preliminary responseThe patent owner has the right to file a preliminary response setting out reasons why no review should be instituted because the petition fails to meet a requirement of the chapter⁷.
3. Institution decisionThe Director may not authorize a review unless the petition and any response show a reasonable likelihood that the petitioner would prevail on at least 1 challenged claim⁴. The decision is due within 3 months after the preliminary response, or after the last date it could have been filed⁴. It is final and nonappealable⁴.
4. TrialThe Patent Trial and Appeal Board conducts each instituted review⁸. The patent owner may file 1 motion to amend, to cancel claims or propose a reasonable number of substitute claims, and either party has the right to an oral hearing⁸.
5. Final written decisionThe final determination must be issued not later than 1 year after the Director notices the institution, and the Director may extend that period by not more than 6 months for good cause shown⁸. If the review is instituted and not dismissed, the Board issues a final written decision on the patentability of each challenged claim⁹.
6. Appeal and certificateA party may request Director Review of the final written decision on limited grounds (37 CFR 42.75)²⁰. A party dissatisfied with the final written decision may appeal under 35 U.S.C. 141 to 144, and any party to the review has the right to be a party to the appeal¹⁰. When the time for appeal has expired or any appeal has terminated, the Director issues a certificate canceling claims finally determined to be unpatentable, confirming those found patentable and incorporating any patentable new or amended claims⁹.

• One-year bar. A review may not be instituted if the petition is filed more than 1 year after the petitioner, a real party in interest or a privy was served with a complaint alleging infringement of the patent (35 U.S.C. 315(b)). The limit does not apply to a request for joinder¹¹.
• Earlier validity suit. A review may not be instituted if, before the petition was filed, the petitioner or a real party in interest filed a civil action challenging the validity of a claim. A counterclaim challenging validity does not count as such a civil action (35 U.S.C. 315(a))¹¹.
• Burden of proof. The petitioner has the burden of proving a proposition of unpatentability by a preponderance of the evidence (35 U.S.C. 316(e))⁸.
• Estoppel. After a final written decision, the petitioner, a real party in interest or a privy may not request or maintain a USPTO proceeding on that claim on any ground that was raised or reasonably could have been raised in the review. The same persons may not assert in a civil action or an ITC proceeding that the claim is invalid on any such ground (35 U.S.C. 315(e))¹¹.

The statute states the minimum for institution, not a right to review. The Director may not authorize an IPR unless the reasonable likelihood threshold in 35 U.S.C. 314(a) is met⁴, and the decision whether to institute is final and nonappealable⁴. Since March 2025 the USPTO has set out how it exercises that discretion in memoranda^12,13. What follows is limited to what the USPTO's own pages and notices state.

• Who decides. By a memorandum of October 17, 2025, the USPTO announced that effective October 20, 2025 the Director will determine whether to institute trial in IPR and PGR proceedings, in consultation with at least three PTAB judges. Institution or denial is ordinarily communicated by summary notice, and an instituted proceeding is referred to a three-member panel of the PTAB¹².
• Discretionary considerations. The USPTO's page on the Director's discretionary process says the Director has broad authority to decide whether to exercise discretion to institute, and will take a holistic view of the facts. Its non-exhaustive list of considerations includes whether the PTAB or another forum has already adjudicated validity of the claims, changes in the law since the claims issued, the strength of the unpatentability challenge, and settled expectations of the parties such as the length of time the claims have been in force¹³.
• Further considerations (2026). A memorandum of March 11, 2026 says that, when determining whether to institute, the Director will consider the extent to which products accused of infringement in a parallel proceeding are made in the United States or tied to US manufacturing investment, the extent to which the patent owner's competing products are made in the United States, and whether the petitioner is a small business that has been sued for infringement of the patent¹⁵. A memorandum of November 17, 2025 treats a petitioner's voluntary search disclosure declaration as a non-dispositive factor favoring institution¹⁶.
• Briefing. For proceedings in which the deadline for the patent owner's preliminary response is after March 26, 2025, the patent owner may file a discretionary denial brief within two months of the notice of filing date accorded, and the petitioner may file a brief in opposition within three months¹³.
• Rulemaking. On October 17, 2025 the USPTO published a proposed rule to modify the rules of practice for IPR institution (90 FR 48335)¹⁴. It is a proposal, not a final rule, so check the PTAB pages for what applies on the date you file.

The decision below is the US Supreme Court's ruling on the constitutionality of inter partes review. It is an example of how the term is used in US law, and says nothing about either party beyond the decision itself.

Decided April 24, 2018. The Court held that inter partes review violates neither Article III nor the Seventh Amendment, describing it as a reconsideration of the government's grant of a patent, which is a matter involving public rights3.