For most independent inventors, the day a patent is granted feels like the finish line. It may start a second contest. Since 2012, anyone who wants to knock out an issued U.S. patent has had a fast, specialized venue for doing so: the Patent Trial and Appeal Board, or PTAB. Understanding how the Board works, what it costs, and how to prepare for it is no longer optional knowledge for an inventor who plans to license, partner or enforce. This guide explains the mechanics in plain English, sets out the concerns that inventor advocates have raised, and offers practical defensive strategies you can build into your plans long before anyone files a petition.
Key points
- The PTAB was created by the America Invents Act (AIA) of 2011; its trial proceedings for IPR and PGR began on September 16, 2012.
- Inter partes review (IPR) challenges novelty and obviousness using prior patents and printed publications; post-grant review (PGR) allows nearly any invalidity ground but only within nine months of grant.
- Challengers need only prove unpatentability by a preponderance of the evidence, a lower bar than the “clear and convincing” standard used in federal court.
- Estoppel limits a losing petitioner from relitigating grounds it raised or reasonably could have raised.
- Your best defenses are built early: careful claim drafting, continuation filings, strong documentation, a realistic budget, and an aligned partner.
What the Patent Trial and Appeal Board actually does
The PTAB is an administrative tribunal inside the United States Patent and Trademark Office, staffed by administrative patent judges with legal and technical training. It has two distinct jobs. The first is ex parte appeals: if an examiner rejects your application, you can appeal to the Board. The second is AIA trials: adversarial proceedings in which a third party, usually a company accused of infringement or worried that it might be, asks the Board to cancel claims of an issued patent. These trials, mainly inter partes review and post-grant review, are the focus of this article. (A transitional covered business method program expired in 2020.)
The AIA trial system was designed by Congress, as part of the America Invents Act, to be a faster and cheaper alternative to challenging patent validity in federal court. Whether it has struck the right balance is one of the most debated questions in modern patent policy.
IPR and PGR basics
Inter partes review (IPR)
Inter partes review is by far the most common AIA trial. Its key features are:
- Who can file: almost anyone other than the patent owner. A challenger does not need to have been sued.
- When: after the later of nine months from grant or the end of any post-grant review. However, if the petitioner has been served with a complaint alleging infringement of the patent, it must file within one year of that service.
- Grounds: only lack of novelty (35 U.S.C. § 102) and obviousness (§ 103), and only on the basis of prior patents and printed publications. Arguments about prior public use, on-sale activity, eligibility or inadequate written description are not available in an IPR.
- Institution threshold: the petitioner must show a “reasonable likelihood” of prevailing on at least one challenged claim.
Post-grant review (PGR)
Post-grant review is broader but available for only a short window:
- When: within nine months of the patent’s grant or reissue, and only for patents examined under the first-inventor-to-file system (generally those with an effective filing date on or after March 16, 2013).
- Grounds: nearly any ground of invalidity, including subject-matter eligibility, lack of enablement, indefiniteness, prior use and on-sale bars.
- Institution threshold: the petitioner must show it is “more likely than not” that at least one claim is unpatentable, or raise a novel or unsettled legal question important to other patents.
The typical timeline
Both proceedings follow a similar statutory rhythm. The table below summarizes the main stages for an IPR; PGR is broadly similar.
| Stage | What happens | Approximate timing |
|---|---|---|
| Petition filed | Challenger files petition with prior art, expert declarations and fees | Day 0 |
| Notice of filing date | Board accords a filing date and notifies the patent owner | Usually within weeks |
| Patent owner preliminary response | Optional response arguing the petition should be denied | Within 3 months of the notice |
| Institution decision | Board decides whether to start a trial | Within 3 months of the preliminary response deadline |
| Trial phase | Patent owner response, discovery (mainly expert depositions), petitioner reply, possible motion to amend, oral hearing | Roughly 9 to 10 months |
| Final written decision | Board rules on patentability of each challenged claim | Within 1 year of institution (extendable up to 6 months for good cause) |
| Appeal | Either party may appeal to the U.S. Court of Appeals for the Federal Circuit | Often another year or more |
The legal standards that matter
Three standards shape the outcome of most PTAB trials:
- Burden of proof. In an AIA trial, the petitioner must prove unpatentability by a preponderance of the evidence, meaning “more likely than not.” In federal court, by contrast, an issued patent is presumed valid and a challenger must prove invalidity by clear and convincing evidence, a standard the U.S. Supreme Court confirmed in Microsoft v. i4i (2011). The same patent can therefore survive in court and fall at the Board on the same evidence.
- Claim construction. For petitions filed on or after November 13, 2018, the Board interprets claims using the same standard as federal courts (the Phillips standard), replacing the older and generally broader “broadest reasonable interpretation” approach.
- Institution scope. Since the Supreme Court’s 2018 decision in SAS Institute v. Iancu, if the Board institutes a trial, it must decide the patentability of every claim the petitioner challenged.
The constitutionality of the IPR system itself was upheld by the Supreme Court in Oil States v. Greene’s Energy (2018). In United States v. Arthrex (2021), the Court held that the USPTO Director must have the power to review Board decisions, which led to the current Director Review process.
Estoppel: the rule that limits repeat challenges
Once the Board issues a final written decision in an IPR, the petitioner (and its real parties in interest and privies) is estopped from asserting, in court or at the USPTO, that a claim is invalid on any ground it “raised or reasonably could have raised” during the IPR. PGR estoppel works the same way but is broader in effect, because a PGR can raise almost any ground. Estoppel is an important protection for patent owners, but it has limits: it applies only to the specific petitioner and those connected to it, it attaches only after a final written decision, and it does not prevent challenges based on evidence that could not be raised in an IPR, such as a physical product that was on sale before the filing date.
Discretionary denial and a shifting policy landscape
The statute gives the USPTO Director discretion over whether to institute a trial, even when the petition meets the threshold. Over the past several years, the Office’s approach to so-called discretionary denial, for example when parallel court litigation is far advanced or when the patent has been in force and relied upon for many years, has changed repeatedly through memos, precedential decisions and proposed rules. Since 2025, USPTO leadership has taken a notably more active role in institution decisions. Because these policies continue to evolve, any inventor facing or anticipating a petition should ask a registered practitioner for the current rules rather than relying on articles, including this one.
Why inventor advocates are concerned
From the perspective of many independent inventors and inventor organizations, including the viewpoint presented on this site, the AIA trial system shifted the balance of power toward large, well-funded challengers. It is worth stating these concerns clearly while recognizing that others see the system differently.
- Two bites at the apple. An accused infringer can defend in court and, in parallel, attack validity at the Board under a lower burden of proof. Inventor advocates argue this doubles the cost and risk of enforcing a patent.
- Uncertainty for investors. If a granted patent can be cancelled years later, a patent is a less reliable asset to finance. Advocates contend this discourages investment in early-stage inventors and pushes them toward selling out to large incumbents.
- Multiple petitions. A single patent may face several petitions from one or more challengers, each requiring a response. For an individual inventor, even a handful of petitions can be financially overwhelming.
- Cost asymmetry. A large company can treat PTAB fees as a routine legal expense. For a solo inventor, the cost of a defense may exceed the money spent obtaining the patent in the first place.
Supporters respond that IPR is cheaper and faster than court litigation, that technical judges are well suited to evaluate prior art, and that the process removes patents that should never have issued. A balanced view recognizes both: the PTAB is a real check on low-quality patents and a real burden on legitimate inventors who lack resources. That tension is part of why this site advocates a broader rethink of patent policy, explored in our article on the Venetian Patent Statute of 1474 and the original purpose of patents.
Defensive strategies for independent inventors
1. Draft claims for the fight, not just for allowance
Many patents fall at the PTAB because they were drafted to get past an examiner, not to survive a well-funded challenger. Work with your practitioner on:
- A layered claim set with broad independent claims supported by progressively narrower dependent claims. If the broad claim falls, a narrow claim that still covers the commercial product may survive.
- Claims tied to concrete technical features that distinguish the invention from what came before, rather than functional language that reads on a wide range of prior art.
- A thorough prior-art search before filing, so that you, not a future challenger, discover the most relevant references first and draft around them.
- A rich specification with multiple embodiments, test data and explanations of why the invention works. This supports later amendments and helps defend against obviousness arguments.
2. Keep a continuation application pending
A pending continuation application in the same patent family is one of the most useful tools an inventor can have. If a parent patent is challenged, the continuation allows you to pursue new claims that avoid the cited prior art and target competitors’ actual products. It also signals to challengers that cancelling one patent will not end the matter. The trade-off is cost, so discuss with your practitioner how long it makes sense to keep the family alive.
3. Document the evidence of non-obviousness
Obviousness is the most common ground in PTAB trials. Patent owners can rebut it with “objective indicia,” sometimes called secondary considerations: commercial success tied to the claimed features, long-felt but unmet need, failure of others, industry praise, copying by competitors, and licensing. These arguments only work if there is evidence. Keep dated records of test results, customer feedback, partner interest, competitor attempts, and trade publications that describe the problem your invention solves. Our guide to protecting your idea before the patent explains how to build these records from the start.
4. Consider your own reexamination strategy
If you discover a troubling piece of prior art after grant, you can ask the USPTO to examine it yourself, through ex parte reexamination or supplemental examination, before a challenger uses it against you. A patent that has already been confirmed over a reference is harder to attack on that reference later. This is a strategic decision to make with counsel, since it reopens prosecution.
5. Plan the budget before you enforce
Assume that any serious assertion against a well-funded company may trigger a petition, and plan before sending a demand letter. Ask practitioners to estimate a preliminary response, a full trial and an appeal, and explore contingency arrangements, litigation funding, insurance, or a partner who will share the cost.
6. Bring in a partner with aligned interests
This is where the Pre-Patent Pre-Partnering strategy becomes a defensive tool as well as a commercial one. A major industry partner that has licensed or co-invested in your technology has a direct interest in keeping the patent alive. It brings legal budget, technical experts, and the market credibility that supports arguments about commercial success. A challenger may also think twice before attacking a patent backed by a serious industry player. Our guide on how to find the right major partner explains what to look for.
A pre-enforcement readiness checklist
- Have you obtained a professional opinion on the validity of your key claims against the best prior art you can find?
- Do your claims include narrower dependent claims that still cover your commercial product or a partner’s product?
- Is a continuation application pending in the patent family?
- Have you collected dated evidence of commercial interest, industry need, and any copying?
- Do you know whether the nine-month PGR window is still open on your patent?
- Have you estimated the cost of a preliminary response, a full trial and an appeal, and identified who will pay?
- Does a partner, investor or licensee share the risk and the reward of defending the patent?
If you answer “no” or “not sure” to several of these, it may be wise to strengthen your position before asserting the patent. Our Invention Readiness Check can help you think through the broader commercial picture.
A note on perspective
None of this means an independent inventor should avoid patents or enforcement. It means the old model of “get the patent, then sue the infringer” is riskier than many assume. In our view, the stronger path is to protect the invention, develop it until its value is visible, and find a committed partner before the patent becomes a target. This article is educational and is not legal advice; consult a registered patent attorney or agent, ideally one with Board experience, about your own patents.
Want help thinking through your patent’s exposure and your partnering options? Contact us by email to start a confidential conversation about your invention and the kind of partner that could help you defend and commercialize it.
