As an inventor, you know everything there is to know about your invention. But you likely know very little about how and when a patent can be challenged. For one, did you know that a patent can be challenged even after it is granted? It’s possible to challenge a patent even after the U.S. Patent and Trademark Office (USPTO) has granted it. The new America Inventions Act (AIA) allows petitioners, competitors, and just about anyone to challenge an approved patent through a Post-Grant Review (PGR) or an Inter-Partes Review (IPR).

These two provisions help keep patents in check. As post-grant review attorneys, we have seen our clients face this situation. Knowing what these processes mean can help you protect your patent, whether you are the owner or a petitioner.

What Is a Post-Grant Review?

A post-grant review is one way to challenge a patent after it is granted. Anyone can file this review immediately after the USPTO grants the patent. There is no waiting period, but there is a deadline. A PGR must be filed within nine months after the patent is granted.

A PGR covers grounds like a lack of patent validity because the invention is non-novel or obvious. It also covers grounds such as invalid specifications or an overly broad patent. In short, the post-grant review covers overall patent validity. It was designed to finish the review proceedings quickly and efficiently.

The new laws are complex. If you are facing this situation, consult a post-grant review attorney immediately. Your lawyer can help you understand the details and take the necessary steps to handle such claims.

What Is Inter-Partes Review?

An inter-partes review is another way to question a patent’s validity after the USPTO has granted it. It can be filed against first-to-invent and first-inventor-to-file patents. Anyone other than the patent owner can file an IPR. 

Unlike the PGR, there is a waiting period of nine months for IPR. It’s better to consult a competent inter-partes review lawyer immediately during this time. Your lawyer will analyze your case and determine the next steps.

Understand the Key Differences Between PGRs and IPRs

Although both methods help ensure the validity of a patent, they are not the same. The key differences between the two include:

1. Timing of Filing

The first major difference is the timing of filing. As a petitioner, you can file the post-grant review immediately after the patent is granted. You have to file it within nine months from the date the patent is issued. On the other hand, you must wait nine months after the patent is issued or after the PGR proceedings are over to file an inter-partes review.

2. Scope of Grounds

Another major difference is what each review focuses on. An inter-partes review focuses only on prior art and patentability. However, a post-grant review covers all grounds for questioning a patent’s validity. Compared to an IPR, a PGR covers more grounds.

3. Applicability to Different Patents

Not all patents are eligible for both proceedings. The Leahy-Smith America Invents Act (AIA) went into effect on March 16, 2013. So, PGR applies to patents with at least one claim with priority after March 16, 2013. However, unlike PGR, IPR is not limited to patents issued after March 16, 2013.

4. Discovery and Amendment Procedures

The rules for finding evidence and changing patent claims differ in IPR and PGR. In an inter-partes review, the discovery process is more limited. It focuses on finding evidence about existing patents or printed publications. 

On the other hand, a post-grant review provides a broader discovery process. It looks into issues like how a patent was written and other matters affecting its validity. Any skilled post-grant review attorney will tell you that where there’s more ground to cover, there are more strategies to use.

Talk to The Skilled Lawyers at Emerson Thomson Bennett

As you can see, inter-partes and post-grant reviews are two different ways to challenge the validity of a patent after it’s granted. These proceedings help ensure each patent is fair. Whether you are the owner or a petitioner, choosing the right process can help you take concrete legal steps. Hopefully, knowing the key differences between PGR and IPR can help you make an informed decision.

Our reliable attorneys are here to help you with Post-Grant Review and Inter-Partes Review filings. We can help you protect your invention. Contact Emerson Thomson Bennett today to get started.



We provide complete intellectual property representation to business owners, inventors and artists in all matters related to the establishment and protection of domestic and international patents, trademarks and copyrights. Attorneys at our firm also serve as in-house IP counsel for companies whose needs do not call for a full-time internal position.






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