Starting a Post-Grant Proceeding: The Different Threshold Standards

Every USPTO proceeding for challenging an issued patent begins with a screening step. Someone asks the Office to take another look, and the Office decides whether the request is strong enough to justify a full proceeding. The America Invents Act created new screening tests for inter partes review and post-grant review while keeping the older test for reexamination.

Knowing which test applies, and how much discretion sits on top of it, is the starting point for choosing a proceeding.

Inter partes review: reasonable likelihood

Under 35 U.S.C. § 314(a), the Director may not authorize an IPR unless the petition and any preliminary response show a reasonable likelihood that the petitioner would prevail with respect to at least one of the claims challenged. The test is claim-focused and asks whether the petitioner is likely to succeed, not merely whether a question has been raised.

By rule, the Board decides institution on the Director’s behalf (37 C.F.R. § 42.4(a)). The petition has to carry the case on its own, which is why its contents matter so much; see the basics of an IPR petition.

Post-grant review: more likely than not

Post-grant review, available during the first nine months after grant for patents subject to the first-inventor-to-file provisions, has a higher bar. Under 35 U.S.C. § 324(a), the petition must show that it is more likely than not that at least one challenged claim is unpatentable.

Section 324(b) provides an alternative route: a petition may also be instituted if it raises a novel or unsettled legal question that is important to other patents or patent applications. This reflects PGR’s broader scope, which allows challenges on grounds such as eligibility, written description and enablement.

Reexamination and supplemental examination: substantial new question

Ex parte reexamination uses the older test. Under 35 U.S.C. § 303, the Director determines whether a request raises a substantial new question of patentability, based on patents and printed publications. Supplemental examination, available only to the patent owner, uses the same phrase under § 257: if the information submitted raises a substantial new question, the Office orders reexamination.

The substantial-new-question test asks whether a reasonable examiner would consider the information important to patentability. It does not require a showing that any claim is likely unpatentable, which makes it a lower bar than either AIA trial test.

Comparing the thresholds

Proceeding	Statute	Threshold	Who may request
Inter partes review	35 U.S.C. § 314(a)	Reasonable likelihood the petitioner would prevail on at least one claim	Anyone other than the patent owner
Post-grant review	35 U.S.C. § 324(a)–(b)	More likely than not at least one claim is unpatentable, or a novel or unsettled legal question important to other patents	Anyone other than the patent owner
Ex parte reexamination	35 U.S.C. § 303	Substantial new question of patentability	Anyone, including the patent owner
Supplemental examination	35 U.S.C. § 257	Substantial new question of patentability	Patent owner only

Meeting the threshold is not enough

The statutory language for IPR is permissive: the Director “may not” institute unless the threshold is met, but nothing requires institution when it is. The Office has treated institution as discretionary.

Section 325(d) adds a specific basis for declining review. In deciding whether to institute an IPR, PGR or reexamination, the Director may take into account whether the same or substantially the same prior art or arguments were previously presented to the Office, for example during original examination.

The Office has also declined to institute for reasons such as parallel litigation and repeated petitions against the same patent. Discretionary-denial practice has changed repeatedly through precedential decisions, memoranda and proposed rules, so anyone evaluating a petition should check current USPTO guidance rather than relying on older summaries.

Limited review of institution decisions

In Cuozzo Speed Technologies, LLC v. Lee (2016), the Supreme Court held that 35 U.S.C. § 314(d), which makes the institution decision “final and nonappealable,” generally bars judicial review of the Board’s decision to institute, at least where the challenge is closely tied to the application of the institution statutes. The Court left room for review of constitutional questions and certain other issues. In practice, a petitioner denied institution has little recourse in court, and a patent owner cannot usually undo an institution decision on appeal from the final written decision.

Key takeaways

• IPR requires a reasonable likelihood of prevailing on at least one claim; PGR requires that a claim be more likely than not unpatentable, or a novel or unsettled legal question.
• Ex parte reexamination and supplemental examination use the lower substantial-new-question test.
• Meeting the threshold does not guarantee institution; § 325(d) and broader discretion allow denial.
• Institution decisions are generally not appealable after Cuozzo (2016).
• Discretionary-denial practice changes often; check current USPTO guidance.