Ex Parte Reexamination: Process, Strategy, and Key Issues

Key Takeaways

• Ex parte reexamination allows the USPTO to re-review an issued patent based on prior art, even years after issuance.
• A substantial new question of patentability (SNQ) must be raised, usually based on patents or printed publications not previously considered.
• Proceedings are generally completed within two years and involve only the patent owner and USPTO.
• Benefits include reduced litigation costs, increased investor confidence, and the ability to challenge questionable patents anonymously.
• Drawbacks include limited participation for third-party requesters and the possibility of strengthening the challenged patent.
• Ex parte reexamination differs from inter partes review (IPR), particularly in participation rights, anonymity, and estoppel effects.
• Recent developments highlight how ex parte reexaminations may run concurrently with PTAB proceedings like IPRs, adding strategic considerations.

What Is Ex Parte Reexamination?

Ex parte reexamination is a tool that allows a patent owner or a third party to lodge a request for the United States Patent Office (USPTO) to reexamine an already-granted patent based on other patents and publications that they bring to the USPTO's attention.

An ex parte reexamination can be requested at any time during the enforceability of the patent. The requester needs to establish that the prior art creates a substantial and new question of patentability (SNQ). The reexamination is conducted in front of a panel of three experienced examiners within a specialized unit of the USPTO called the central reexamination unit (CRU).

Ex parte reexamination proceedings involve only the patent owner and the USPTO. After the request is filed, the third-party requester is removed from further involvement unless the patent owner files a statement seeking to rebut their assertions.

Requests for continued examination (RCEs) are not available in ex parte reexamination proceedings. No legal estoppel is created by an ex parte reexamination proceeding.

Ex parte reexamination has been available since 1981 and continues to be available under the America Invents Act (AIA).

Strategic Use of Ex Parte Reexamination

Ex parte reexamination can be used strategically by both patent owners and third parties. For patent owners, it provides an opportunity to strengthen a patent by clarifying claims and ensuring validity against overlooked prior art. For third parties, it offers a lower-cost and less adversarial alternative to litigation. Because the process is largely conducted between the USPTO and the patent owner, requesters can remain anonymous and avoid being directly involved in lengthy proceedings.

This anonymity makes ex parte reexamination a valuable tool in competitive industries, where businesses may want to challenge a rival’s patent without revealing their identity or litigation strategies.

Substantial New Question of Patentability

A substantial new question (SNQ) is a way to reduce harassment of patent owners by forcing the third-party requester to show that the questions against the patent have enough weight.

The SNQ needs to originate from a prior patent or a printed publication. An SNQ is not a proposed ground for rejecting a patent. Not all previously considered references, such as old art, or unconsidered references, such as new art, can raise an SNQ. Old art can be used to support an SNQ only if it is shown in a new light. New art can be used to support an SNQ only if the technological teaching relied upon in the art has not already been considered by the office in earlier reviews of the patent.

Standards Applied by the USPTO

When determining whether an SNQ exists, the USPTO does not need to establish unpatentability at the outset. Instead, it must only find that the prior art raises a question worth reconsidering. Importantly, the threshold for instituting reexamination is lower than for litigation or PTAB reviews.

The USPTO examines the prior art in light of the patent claims under the “broadest reasonable interpretation” standard. This standard gives the Office significant latitude to challenge claims, often resulting in amendments or cancellations that reshape the scope of the patent.

Timeline for Ex Parte Reexamination

The USPTO aims to have ex parte reexamination completed in a timeline of fewer than two years.

• Month 0 - A request for an ex parte reexamination is made.
• Month 3 - The central reexamination unit needs to decide whether they will grant or deny the request within three months of the request being made.
• Month 4 - If the request is denied, the requester has one month to petition for reconsideration.
• Month 5 - If the request is granted, the patent owner has two months to file a statement responding to the questions being posed and to amend their claim if they wish to. Filing a statement is optional and it usually isn't done.
• Month 7 - If the patent owner does decide to file a statement, the requester has two months to file a reply statement if they wish to.
• Months 6-8 - A First Action needs to be issued within one month from the expiration of the patent owner's 2-month window of filing a statement.
• Months 8-12 - The patent owner then has two months to respond to the First Action. This can be shortened to one month if there are pending proceedings like litigation or reissue. Extensions may be given if sufficient cause is shown. The patent owner can also ask for an interview during this time.
• Months 12-24 - During the second year, several things can take place:
  • The second Office Action in the reexamination proceedings is made final.
  • The CRU has an internal goal of issuing a Final Office Action within two years from the filing date of the request.
  • The period for response to a final rejection is usually two months, but it can be shortened to one month. A response after the final rejection does not automatically get entered or filed. If the CRU does decide to file it, the time period is automatically extended by one month.
  • If the response does not place all claims in a condition where they are patentable, the examiner will issue an advisory action providing the patent owner enough time to consider the action and either file a notice of appeal or a second response that clearly places all claims in conditions where they are patentable.
  • The patent owner can appeal any decision that changes the status of their patent to either the USPTO or in court.
  • Upon conclusion of the reexamination proceeding, the examiner will issue a Notice of Intent to Issue Ex Parte Reexamination Certificate (NIRC), which sets forth the status for each claim that was made.
• Month 25.7 (average) - The reexamination is issued.

Factors Affecting Duration

While the USPTO strives to complete reexaminations within two years, the actual timeline can vary. Cases involving multiple requests for reexamination, complex technology, or concurrent proceedings such as litigation or inter partes review may extend the process.

In some situations, courts may stay litigation pending the outcome of a reexamination. This stay can benefit accused infringers by delaying expensive court battles while the USPTO reevaluates the patent.

Benefits of Ex Parte Reexamination

Ex parte reexamination proceedings can offer three main benefits.

• A reexamination proceeding can settle validity disputes quicker and cheaper than litigation.
• Reexamination proceedings allow courts to refer patent validity questions to the expertise of the Patent Office.
• A reexamination proceeding reinforces investor confidence in the certainty of patent rights by giving the USPTO an opportunity to review doubtful patents.

In addition to these overall benefits, ex parte reexamination also benefits the third-party requester in several ways:

• Anyone can file a request for an ex parte reexamination.
• There are no jurisdic­tion or other requirements to be a third-party requester.
• Third-party requesters can remain anonymous.
• Once a reexamination is requested, it continues until a reexamination certificate is issued. It can't be withdrawn.
• As soon as the reexamination is ordered, the patent in question no longer has a presumption of validity.
• During reexamination, claims are given their broadest reasonable interpretation.
• The patent owner's amendments and arguments can create prosecution history estoppel.
• A Request for reexamination can be filed up to the six additional years of enforceability of the patent with respect to a patent infringement after the patent has expired.
• A reissue application can't be filed after the term of the patent has expired.
• If there are additional requests for reexamination, they can be filed on additional substantial new ques­tions of patentability of the patent claims and merged with the current reexamination proceeding.
• Claim amendments made during the proceedings can provide intervening rights to the infringer.

Drawbacks of Ex Parte Reexamination

Ex parte reexamination can have several drawbacks for the third-party requester that should be clearly understood and considered before filing for an ex parte examination.

• Third-party requesters cannot take part in the proceedings once the initial request has been made.
• Third-party requesters can't appeal any decisions that the patent claims are patentable prior to issuance of a reexamination certificate.
• A third-party requester can't stop the issuance of a reexamination certificate that deter­mines certain claims patentable.
• A third-party requester can't stop a patent owner from amending the existing claims or adding claims of the same scope to make their claim stronger.
• The third-party requester can't stop a broadened reissue from being filed by the patent owner and having the ex parte reexamination proceeding merge with the new application.
• Third-party requesters can't stop ex parte interviews from the examiner and patent owner, nor can they take part in the interviews.
• A reexamination certificate may be issued, meaning that the original patent will have gone through two USPTO decisions. This will make that patent even more valid.

Ex Parte Reexamination Versus Inter Partes Reexamination

The post-grant patent world changed forever on September 16th, 2012. On this date, inter partes patent reexamination was discontinued and replaced with the Inter Partes Review (IPR) proceeding. IPR proceedings can be used to challenge any patent, regardless of vintage. The USPTO fee to request an ex parte patent reexamination then rose from $2,520 to $17,750.

• Both ex parte and inter partes reexamination submits a patent to an examination process similar to the original process it went through when the patent was issued.
• Ex parte reexamination can be requested by anyone at any time, but only the patent owner participates in the reexamination proceeding.
• In inter partes reexamination, the third-party requester can actually take part in the reexamination proceedings.
• Unlike ex parte reexaminations, inter partes reexamination requests are not anonymous. The third-party requester has to be identified. Inter partes reexamination requests can only be filed against patents issued from an application filed in the United States on or after November 29, 1999.
• In an inter partes reexamination, the third-party requester is allowed to file comments in response to submissions made by the patent owner, and they can appeal the USPTO's decisions.
• The estoppels created because of an inter partes reexamination and any further litigation are among the most important differences between the two.
• Estoppels in an inter partes reexamination flow two ways:
  • From the inter partes reexamination to the civil action.
  • From the civil action to the inter partes reexamination.
• If the technology is simple and the prior art is substantial, the ex parte review will allow the challenge to move forward with a minimum of investment in attorney and USPTO fees.
• IPR is better than ex parte patent reexamination in terms of ability to participate and demonstrate unpatentability, but the cost of such participation is substantial.
• In order to be granted a request for inter partes reexamination, you need to show that there is a reasonable likelihood that you will win with respect to at least one claim.

Ex Parte Reexamination and Inter Partes Review (IPR)

Since inter partes reexamination was replaced by IPR in 2012, many challengers prefer IPR due to the ability to actively participate in the proceeding. However, ex parte reexamination remains attractive for its lower costs, anonymity, and the absence of estoppel that attaches to IPR decisions.

Recent cases show that ex parte reexaminations can proceed in parallel with IPRs at the Patent Trial and Appeal Board (PTAB). For example, in 2025, the PTAB instituted an IPR even though an ex parte reexamination on the same patent was ongoing. This demonstrates that the USPTO may allow both processes to move forward simultaneously, creating additional layers of strategy for litigants and patent owners.

Required Elements of a Reexamination Request

An ex parte reexamination request needs to have:

• A statement that points out each substantial and new question being raised.
• A detailed explanation that demonstrates the connection between the cited patents to every claim for which reexamination is requested.
• A copy of every patent or printed publication where there are substantial and new questions.
• A copy of the patent for which the reexamination is requested.
• Certification that a copy of the request has been served on the patent owner.
• The fee payment.

An inter partes reexamination request needs to contain:

• Identification of the patent in question and every claim for which reexamination isi requested.
• Citation of the patents and printed publications for the substantial and new questions.
• A statement that points out each substantial and new question.
• A copy of every patent or printed publication relied upon in the substantial and new questions.
• A copy of the patent that is being requested for reexamination.
• Certification from the requester that a copy of the request has been served to the patent owner.
• Certification by the requester that the estoppel provisions do not prohibit reexamination.
• A statement identifying the third-party requester.

Practical Considerations for Requesters

Before filing, requesters should weigh the costs, benefits, and risks:

• Costs: Although less expensive than litigation or IPR, the filing fee for an ex parte reexamination request is substantial, and attorney fees can add up.
• Patent Owner Reaction: Amendments made during reexamination could make the patent stronger, potentially creating more challenges for competitors.
• Timing: A request can be filed even after the patent term expires, provided enforceability continues (e.g., for damages from past infringement).
• Concurrent Proceedings: If litigation or IPR is ongoing, requesters should consider how reexamination may influence those proceedings and whether courts are likely to stay litigation.

These considerations underscore the importance of developing a broader IP strategy when using reexamination as a tool.

Frequently Asked Questions

1. Who can file an ex parte reexamination request?
   Anyone, including competitors and anonymous third parties, can file a request as long as they provide prior art that raises a substantial new question of patentability.
2. How long does an ex parte reexamination take?
   The USPTO aims to complete reexaminations within two years, but complex cases or concurrent litigation may extend the timeline.
3. What happens to ongoing litigation if a reexamination is requested?
   Courts may grant a stay of litigation until the USPTO resolves the reexamination, which can reduce costs for the accused infringer.
4. How does ex parte reexamination differ from IPR?
   Unlike IPR, requesters in ex parte reexamination cannot participate after filing, remain anonymous, and are not bound by estoppel.
5. Can a patent become stronger after reexamination?
   Yes. If the patent owner successfully amends claims or rebuts challenges, the patent may emerge from reexamination more enforceable than before.

If you need help with ex parte reexamination, you can post your legal need on UpCounsel's marketplace. UpCounsel accepts only the top 5 percent of lawyers to its site. Lawyers on UpCounsel come from law schools such as Harvard Law and Yale Law and average 14 years of legal experience, including work with or for companies like Google, Menlo Ventures, and Airbnb.