Information on Filing Post-Grants or Inter Partes Reviews

If you have ever looked at a patent and thought, “That seems awfully confident for something built on shaky ground,” welcome to the world of post-grant review and inter partes review. These proceedings, usually called PGR and IPR, give third parties a way to challenge issued U.S. patents before the Patent Trial and Appeal Board, or PTAB. They are not casual paperwork exercises. They are high-stakes, deadline-driven, evidence-heavy proceedings where the difference between “smart strategy” and “expensive regret” can be one missed filing date, one weak expert declaration, or one petition that tries to do too much.

This guide explains how filing post-grant reviews or inter partes reviews works in plain English, with enough detail to help business owners, inventors, in-house counsel, and curious readers understand the process. It is educational only, not legal advice. Still, if you want a practical map of the terrain before stepping into the PTAB arena, you are in the right place.

What Are Post-Grant Reviews and Inter Partes Reviews?

Both PGR and IPR are administrative patent challenges handled by the PTAB at the U.S. Patent and Trademark Office. They are designed to let a party ask the Board to cancel one or more patent claims as unpatentable. Think of them as specialized patent validity contests with strict rules, tight schedules, and very little patience for sloppy work.

The key difference is timing and scope. A post-grant review is available only in a short window after patent issuance and generally offers a broader menu of invalidity arguments. An inter partes review usually comes later and is narrower in the grounds it allows, but it remains the more common tool in practice.

In simple terms, PGR is the broader but shorter-lived opportunity. IPR is the narrower but more familiar workhorse.

When to Choose PGR and When to Choose IPR

Choose PGR when broad invalidity arguments matter

PGR can be powerful because it is not limited to patents and printed publications. That means a petitioner may raise a wider range of issues, such as patent eligibility under Section 101, written description, enablement, and indefiniteness. If the patent looks vulnerable because the claims are abstract, the disclosure is thin, or the language is mushy enough to spread on toast, PGR may be the better fit.

Example: Imagine a newly issued software patent with broad claims that appear to describe a business concept dressed in technical clothing. If you believe the claims fail under subject-matter eligibility or the specification does not adequately support the full claim scope, PGR gives you room to make those arguments.

Choose IPR when prior art is your best weapon

IPR is usually the preferred route when your strongest attack rests on prior patents, published applications, journal articles, standards documents, or other printed publications. It is narrower, yes, but sometimes narrower is better. PTAB panels appreciate focused petitions that say, in effect, “Here are the claims, here is the prior art, here is why this should never have survived examination.”

Example: Suppose a patent owner sues your company over a hardware patent, and your team uncovers two earlier patents plus a technical paper that appear to teach every meaningful claim element. That is classic IPR territory.

The Filing Windows You Cannot Afford to Miss

This is where strategy becomes calendar management, and calendar management becomes survival.

PGR deadline

A petition for post-grant review must be filed no later than 9 months after the patent grants or the reissue patent issues. Miss that window, and PGR is gone. Not “probably gone.” Gone.

IPR deadline

For many patents, an inter partes review petition can be filed only after the 9-month post-grant window closes, or after any instituted PGR ends. But there is another crucial deadline: if the petitioner, its real party in interest, or its privy was served with an infringement complaint, the petition generally must be filed within 1 year of service. That one-year bar is one of the biggest traps in PTAB practice.

Translation: if you are already in district court litigation, you do not have endless time to “think about maybe filing an IPR someday.” PTAB strategy often has to be built early, sometimes before the first scheduling conference stops being polite and starts getting real.

The declaratory judgment trap

There is also a civil-action bar to keep in mind. A party that files a civil action challenging patent validity before filing its PTAB petition can block itself from obtaining institution. In other words, do not sprint into court first and then expect the PTAB to happily clean up the strategy later.

What a Strong Petition Needs

A petition is not just a complaint with better formatting. It is the core merits brief. If institution is the gate, the petition is the key. A weak petition rarely improves with age.

1. A clear claim-by-claim roadmap

The PTAB expects a disciplined presentation. Identify the claims being challenged, explain the claim construction issues that matter, and walk the Board through the invalidity theory one limitation at a time. Vagueness is not a strategy. It is a donation.

2. The right evidence

In IPR, your case lives or dies on patents and printed publications. In PGR, your evidence may be broader, but it still must be tightly tied to the claims and legal standards. Expert declarations are often critical, especially when the petition depends on how a person of ordinary skill in the art would read the references or combine them.

3. Real-party-in-interest accuracy

PTAB rules require mandatory notices, including identification of each real party in interest and related matters. This sounds administrative until it is not. Mistakes here can create time-bar fights, estoppel problems, or awkward procedural detours that nobody enjoys except possibly the other side.

4. Respect for word limits

IPR petitions are subject to a 14,000-word limit, while PGR petitions get 18,700 words. That sounds generous until you start explaining ten claims, four references, one expert, two alternative combinations, and a side order of claim construction. Good PTAB writing is lean, direct, and allergic to throat clearing.

What Happens After Filing?

Once the petition is filed and served, the patent owner may file a preliminary response. That response usually argues why the Board should not institute trial. The PTAB then decides whether to institute. By statute, the institution decision generally comes within 3 months after the preliminary response is received, or after the response deadline passes if none is filed.

If the PTAB institutes review, the case moves on a relatively fast track. A final written decision is generally due within 1 year of institution, though the Board may extend that period by up to 6 months for good cause. Compared with district court litigation, that is brisk. PTAB timing has the energy of someone aggressively organizing their pantry on a Sunday morning: efficient, unforgiving, and not especially interested in excuses.

Institution Standards: Not the Same for PGR and IPR

The Board does not institute every petition just because someone paid the filing fee and used serious-looking fonts.

IPR standard

To institute IPR, the petitioner must show a reasonable likelihood of prevailing on at least one challenged claim. This is a meaningful threshold, but it is lower than having to prove the whole case upfront.

PGR standard

PGR uses a higher institution threshold. The petitioner must show that it is more likely than not that at least one challenged claim is unpatentable, or present a novel or unsettled legal question that is important to other patents or applications. Because the grounds are broader and the timing is earlier, PGR is powerful but demanding.

Costs, Fees, and Budget Reality

PTAB proceedings are usually less expensive than full patent litigation, but nobody should mistake them for a bargain-bin hobby. As of the current USPTO fee schedule, the filing fees alone are substantial. For up to 20 claims, an IPR request fee is $23,750, with an additional $28,125 post-institution fee. For PGR, the request fee is $25,000, and the post-institution fee is $34,375. Extra claim fees may apply.

And that is just the government-fee side of the ledger. Add attorney time, expert work, prior-art searching, technical analysis, and coordination with any district court case, and the true cost climbs quickly. A smart filing plan therefore starts with triage: Which claims matter commercially? Which arguments are strongest? Which proceeding gives the best risk-adjusted outcome?

Claim Construction, Burden of Proof, and Motions to Amend

In both IPR and PGR, the petitioner bears the burden of proving unpatentability by a preponderance of the evidence. The PTAB also applies the same general claim construction standard used in federal court, rather than the old broadest-reasonable-interpretation approach that long haunted patent owners like a procedural ghost.

Patent owners are not helpless spectators. They may file responses and, in appropriate circumstances, seek to amend claims. Motion-to-amend practice has evolved, and the USPTO finalized changes in 2024 that formalized options for preliminary guidance and revised motions to amend. That gives patent owners a more structured route to salvage narrower, better-supported claims, though success still depends on careful drafting and evidentiary support.

The Big Strategic Risk: Estoppel

If you file an IPR or PGR and it results in a final written decision, estoppel can follow. In plain English, the petitioner may later be prevented from raising certain invalidity grounds in the USPTO, district court, or the International Trade Commission if those grounds were raised or reasonably could have been raised in the PTAB proceeding.

This is why PTAB petitions require thought, not adrenaline. File too narrowly, and you may leave useful arguments behind. File too broadly, and you may weaken the petition or create avoidable complexity. The best petition is rarely the longest one. It is the one that selects the strongest grounds with a realistic view of what may be forfeited later.

Practical Filing Tips Before You Pull the Trigger

Audit the litigation timeline

If a complaint has been served, mark the IPR one-year deadline immediately. Then work backward to leave enough time for prior-art searching, expert preparation, petition drafting, and internal approvals.

Decide whether you are solving a legal problem or a business problem

Sometimes a company wants total invalidation. Sometimes it only needs to knock out a few claims to change settlement leverage, licensing posture, or injunction risk. The petition should match the business objective.

Do not challenge every claim just because you can

Overstuffed petitions can look impressive right up until the Board reads them. Focus on claims that matter and grounds you can actually prove.

Coordinate with district court counsel

PTAB and district court strategies should not live on separate planets. Stays, claim-construction positions, expert theories, and estoppel consequences all interact.

Watch current PTAB guidance

Discretionary-denial practice, workload-management procedures, and other PTAB guidance can shift over time. A filing strategy that looked clever last year may need updating this year.

Real-World Experiences and Lessons From Filing IPRs and PGRs

One of the most common experiences in PTAB practice is discovering that the real fight begins long before the petition is filed. Teams often start out thinking the hard part is finding prior art or identifying a legal theory. In reality, the harder task is deciding what not to argue. In many challenged patents, there are five or six possible weaknesses, but only two or three are worth presenting in a way the Board will find clean, credible, and institution-worthy. The experience of many practitioners is that restraint often beats ambition.

Another recurring lesson is that timing pressure changes the quality of the filing. When a party waits until the last stretch of the one-year IPR deadline, everything gets harder. Prior-art searches become rushed. Expert declarations sound hurried. Internal review gets compressed. That usually produces a petition that feels crowded instead of sharp. By contrast, filings prepared with enough runway tend to read more coherently because the team has time to pressure-test the theories, improve charts, and remove weak arguments before they become permanent.

Patent owners have their own familiar experience. Many initially view an IPR or PGR as just another brief to answer, but the PTAB is a specialized forum with its own rhythm. A strong patent owner response usually does more than deny the petition’s assertions. It identifies where the petitioner oversimplified the technology, cherry-picked the prior art, or glossed over claim language that matters. In some proceedings, patent owners also learn that a carefully developed motion to amend can change the tone of the case. It does not always rescue every claim, but it can reposition the dispute from “all or nothing” to “what survives in narrower form.”

There is also a human experience that rarely appears in formal summaries: PTAB cases are intensely document-driven, but they are still shaped by judgment calls. Counsel must decide whether to pursue parallel petitions, whether to challenge all independent claims, whether to rely on one expert or several, and whether to spend precious pages on claim construction or let the invalidity case carry the day. The best teams tend to treat these as strategic design choices, not just legal chores.

Finally, many parties walk away from PTAB practice with the same conclusion: filing a post-grant review or inter partes review is not just about attacking a patent. It is about telling a disciplined story under rules that reward precision. The most effective filings usually combine three things: a strong procedural posture, a limited set of persuasive grounds, and a presentation that makes the Board’s job easier rather than harder. That may not sound glamorous, but in PTAB practice, clarity is often the closest thing to a superpower.

Conclusion

Filing a post-grant review or inter partes review is one of the most important strategic decisions a patent challenger can make. PGR offers a short but powerful opportunity for broad attacks on a newly issued patent. IPR offers a later, more focused path built around prior patents and printed publications. Both can be effective, but both punish weak preparation.

If there is one takeaway, it is this: choose the right proceeding, file on time, build a disciplined record, and never treat the petition like a rough draft. In PTAB practice, your first shot often has to do the work of your best shot. That is not terrifying, exactly. But it is close enough to keep everyone honest.