An Alternative to Claim Mirroring in Initial Patent Application Filing

“Though insight can be gained with mirrored claims, more insight should be available to the patent practitioner when the examiner examines more claims with unique claim scope.”

claimWhile working as a patent examiner at the U.S. Patent and Trademark Office (USPTO) in Art Unit 2121 (artificial intelligence, or AI) I noticed that the typical patent application that I examined had seven method claims, seven apparatus claims, and six computer-readable medium (CRM) claims. In the typical application, the method and apparatus claims were mirrors of each other, and the first five CRM claims were mirrors of claims 1-5 and the last CRM claim combined the subject matter of claims 6 and 7. While examining a typical patent application, I only had to find prior art that taught these seven unique claims to reject the entire patent application. This led me to ponder why applicants are wasting the 13 other claims included with the standard filing fee with mirrored claims. Though best practice is to have multiple statutory categories with mirror claims by the time of allowance for enforceability reasons, there is a potential advantage for the applicant to file fewer mirror claims initially.

Advantages to Filing More Initial Claims with Unique Scope

  • More Avenues to Explore Patentability

With increasing the number of claims that have unique claim scope, more aspects of the invention can be examined for patentability. By drafting claims with varying scope in the initial filing, more patentable subject matter can be explored from both the high-level broad description to the implementation details in the initial patent application examination.

  • Higher Chance of Obtaining Allowable Subject Matter in First Office Action

Having more claims with varying scope should increase the chances of receiving allowable subject matter in the first office action. As a patent practitioner, I like to be able to tell the client we can get a patent with the scope of the allowable subject matter after a first action and then use the client’s goals to determine the next steps. If a client’s goal is to obtain a patent quickly, we can take the allowable subject matter. On the other hand, if the client’s goal is to obtain a broader patent, we can either take the allowable subject matter and file a continuation to work with the patent examiner for the appropriate claim scope, or work with the patent examiner for the appropriate claims scope in the present application. Without allowable subject matter, the only choices are to argue with the patent examiner and/or amend the claims, appeal the case to the Patent Trial and Appeal Board (PTAB), or abandon the application. I think a better starting point with a patent examiner is to craft the claims in a way that encourages the patent examiner to determine the application contains a patentable invention after the first action and to work with the examiner to find the appropriate scope for the invention. Contrast this with a mirrored claim set where the patent examiner initially determines that no claims are patentable. I believe the sooner agreement on patentability can be achieved, the easier the prosecution of the patent application will be. This moves the examiner’s mindset from the view that the invention is not patentable to one of determining the appropriate claim scope.

  • Higher Chance of Relevant Prior Art Made of Record in First Office Action

The more relevant prior art that is on record, the easier it is to draft a patentable claim set. Since some patent examiners will keep a list of references for potential claim amendments the examiner predicts will happen, the examiner may not disclose these references to an applicant in the first action when the features are not claimed. If what the patent practitioner would normally put in a future claim amendment in a traditional claim mirroring approach is in the initial claim set, the examiner will be more likely to reveal these prior art references in the first office action.

  • Expected Lower Prosecution Cost

When the examiner finds relevant prior art for a claim set, typically the claims are amended to avoid the prior art. With this approach, there is a hope that the amendment is not taught in a prior art reference that is not of record. By reducing the number of mirrored claims, it is possible to have more claims with varying scope examined. With more claims of varying scope, the number of office action responses and requests for continuation examination (RCEs) should be reduced, thus reducing the prosecution cost.

  • More Insight into the Examiner

By having more claims examined with varying scope, more information can be gained into the examiner and the examiner’s approach. Though insight can be gained with mirrored claims, more insight should be available to the patent practitioner when the examiner examines more claims with unique claim scope. Also, by having very narrowly focused dependent claims, insight into how reasonable the examiner is can be gained. For example, if the dependent claims are very narrow and the examiner still rejects these claims, then the applicant could determine that the examiner is not reasonable and create an appropriate prosecution strategy, such as, arguing against the patent examiner’s position and planning to appeal based on the expected final rejection. With mirrored claims, this level of insight is usually not available until an RCE is examined. Though examiner analytics can be used to gather insight into the examiner, greater insight can be gleaned from observing exactly how the examiner will respond to this particular case compared to examiner analytics which only looks at the examiner in the aggregate. Every case is different and seeing how the examiner reacts to this particular case is more valuable than seeing how the examiner acts in general.

  • Opportunity to File Additional Continuations with Different Statutory Categories

The fewer mirror claim strategy allows the client the opportunity to obtain multiple patents for their invention and keeps the patent family pending to allow the patenting strategy to be adjusted with changes in the client’s business model and law. For example, if recent case law makes the current patent suspect to patent eligibility (i.e., 35 U.S.C. 101) challenge, a new set of claims can be filed while the patent family is pending. For another example, if the client’s business model pivots and the earlier filed patent application has support for this new business model, future patent applications can be filed for the technology that enables this new business model.

  • Opportunity to Isolate Method, Apparatus, and CRM Claims into Different Patents

With the ever-changing patent law landscape, there may be an advantage in having different statutory categories in different patents. For example, a PTAB challenger would have to file 3 challenges to completely invalidate 3 patents in different statutory categories, which would triple the USPTO fees and increase the patent practitioner cost compared to challenging a single patent that contains multiple statutory categories.

Disadvantages to Filing More Initial Claims with Unique Scope

  • Higher Initial Preparation Fees Due to More Unique Claims

Writing mirror claims only takes an additional few minutes to draft and there are tools to automate claim mirroring. When drafting additional claims with unique claim scope, significantly more time is required.

  • Potential Payment of Excessive Claim Fees

When there are over seven allowable claims and the applicant desires to have mirrored claims in the same patent, Excess Claim Fees would have to be paid for the additional mirror claims. Assuming no excessive claims were initially filed, if there are over seven allowable claims and the client desires to have all the statutory categories in one patent, then excessive claims fees would have to be paid to get all the mirror claims in the issued patent. For example, if 10 method claims were allowable and the client wanted all the claims in the same patent, once the 10 claims are mirrored for the apparatus and the CRM then there would be a total of 30 claims and a fee for 10 excessive claims would have to be paid to the USPTO. I believe even in situations where excessive claims fees are required, the savings in prosecution cost will be an overall cost savings for the client. If I was a client, I would happily pay for extra claims if I knew I would get a patent and not have to pay other costs like office action responses and RCEs. This is especially true given that at the time of publication of this article an additional dependent claim is $100/$40/$20 each for un-discounted/small/micro entity while the professional fee for an office action response generally is in the multiple thousands of dollars.

  • A Potentially Stubborn Examiner

A potential issue with fewer mirrored claims is that once the examiner determines what is patentable in a patent application, the examiner may be unwilling to listen to other viewpoints into what is patentable. This could potentially limit the scope of the invention. A similar situation could also happen with prosecution where mirrored claims are used.

  • Examiner May Not Accept Newly Filed Mirror Claims After Allowable Subject Matter is Found

For example, the patent examiner could issue a restriction requirement when additional statutory mirror claims are added. One way to mitigate issues with adding statutory categories is to initially file independent claims in all statutory categories and write dependent claims in one of these statutory categories. As the examiner does not receive production credit for issuing a restriction requirement, I believe there is a low likelihood the examiner would object to new mirror claims. If this is a concern for the applicant, a quick call to the examiner could clear this hurdle.

  • Examiner May Not Like the Additional Search

Fewer mirrored claims mean more searching for the patent examiner due to more claims with unique claim scope. This may cause the examiner to take shortcuts and to be less willing to work with the patent practitioner in the future. On the flip side, if the patent application is allowed after the first office action, the examiner gets the remaining production credit for the case without having to write a final office action, and wait for the case to either abandon or an RCE filed to get the remaining production credit.

  • First Action Allowance

The examiner has discretion to enter mirror claims after a notice of allowance. Where there is a desire to add mirrored claims after a notice of allowance has been issued, a quick call to the examiner to discuss adding mirror claims should allow the applicant to determine if the patent examiner will enter the new mirror claims. My personal opinion is that unless the patent practitioner intended a narrow claim set, if a first action allowance is issued without an examiner amendment, the claims are too narrowly drafted.

  • Risk of Forgetting to Add Additional Mirror Claims Before Prosecution Closes

As writing fewer mirror claims may not be the best strategy in every patent application, there is a potential risk of the patent practitioner forgetting to add the additional mirror claims before prosecution closes for the applications that had fewer mirror claims initially drafted. This is especially true when a different patent practitioner prosecutes a patent application drafted by another. This risk could be mitigated by creating a checklist for the end of prosecution that reminds the patent practitioner to check if mirror claims need to be added or continuations need to be filed. Another alternative is to build this check into workflow management.

  • Potential of Client Objections

A client may have reservations about filing fewer mirror claims, such as, a hesitance to change when the old system worked or unwillingness to take a risk of how fewer mirrored claims could affect the patent portfolio if the issued patent is litigated. I believe filing fewer mirror claims will most likely be an issue for large patent filers that want uniformity across their patent portfolio. I believe mid/small-size patent filers and independent inventors will be more willing to allow the patent practitioner to write fewer mirror claims. Either way, the client should be part of the decision making process.

  • Effect on Foreign Filings

As my practice has focused on U.S. patent applications and foreign applications in the U.S. phase, I cannot comment on how fewer claim mirroring will affect subsequent foreign filings. If subsequent foreign filings are a concern, one approach can be to initially file the mirror claims in the United States and file a preliminary amendment at the USPTO with a claim set of fewer mirrored claims.           

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Author: kchungtw 


Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of

Join the Discussion

10 comments so far.

  • [Avatar for Anon]
    January 30, 2023 11:04 am

    Prosecution history estoppel is when the applicant narrows the claims and later is barred from recapturing the surrendered matter.

    It is more than that.

    Any words in the record are fodder for being contested in the enforcement stage of a patent, therefore the golden rule is always the less said the better.

    may point is if the applicant can do this with the initial filing, the applicant can save the cost of the RCE.

    Your point is the opposite of reality, as should be immediately clear. When you start with far more (and different) claim terms you will necessarily have more to wrestle with before any first allowance (thereby increasing — not decreasing — the likelihood of incurring RCE’s).

  • [Avatar for Brian Downing]
    Brian Downing
    January 30, 2023 10:01 am


    Can you expand on what you mean by “prosecution history estoppel is necessarily implicated”? Prosecution history estoppel is when the applicant narrows the claims and later is barred from recapturing the surrendered matter. It wasn’t my intention to suggest surrendering matter. I could potentially see issues with a foreign originated case with a preliminary amendment that removes mirror claims. Unless I have a blind spot, I don’t see estoppel issues if the patent application is initially drafted with fewer mirror claims.

    While an examiner with one of my typical applications, I would say something like ‘claim 8 discloses the same subject matter as claim 1 and is rejected for the same reasons as claim 1’, then repeat for mirror claims 9-20. Other examiners will copy and paste the rejection for mirror claims. I don’t see value for an applicant when an examiner is copying and pasting rejections for mirror claims in a first action especially when the applicant can explore more patentable subject matter in the dependent claims.

    Regarding the “savvy practitioners already do this by way of continuation practice” comment, my point is if the applicant can do this with the initial filing, the applicant can save the cost of the RCE. If the art is good in the finial office action, a practitioner will find new matter in the app and amend the claims. The idea behind this article is to discuss the pros/cons of adding the matter in the initial filed claims that would normally not show up until later in prosecution.

  • [Avatar for Brian Downing]
    Brian Downing
    January 30, 2023 09:18 am

    @Max Drei
    Good point on additional patents causing increased maintenance fees.

    In the US, I have not found a restriction requirement for mirror claims. A US patent examiner does not get production credit for issuing a restriction requirement. Since rejecting a mirror claim is basically copying the rejection from where the claim was mirrored, I don’t see is a motivation to issue a restriction requirement with mirror claims. I focus on high tech so other parts of the patent office may be different.

  • [Avatar for Anon]
    January 29, 2023 03:36 pm

    Mr. Lewis,

    Good thoughts – I concur.

  • [Avatar for David Lewis]
    David Lewis
    January 29, 2023 03:15 pm

    Regarding Breeze’s comment, I find that examiners are often more reasonable in their approach to patentability than to restriction requirements. However, I am not recommending for or against mirror claims.

    On the one hand, filing mirror claims helps ensure that the patent issues with the mirror claims (which is likely good).

    On the other hand, there may not be an opportunity to add the claims later (there is a good chance of the Examiner not allowing the addition of mirror claims after the prosecution is closed), and the client may not want to file a continuation or RCE to get the mirror claims.

    Also, the method claims may not have the same value as the system/device claims (for example) and so it may not always be in the client’s best interest to have the same number of method claims as systems/device claims.

    Although some of the comments in the article make assumptions that are not necessarily accurate (as pointed out by Anon, for example), I think there are many acceptable practices and each has some advantages over others.

    Perhaps we all, at least some of the time, could spend a bit more time making sure that the particular set of claims we file is best suited for the client’s needs and desires (no one is perfect). Perhaps, that is the best aspect of this article is (whether you agree with it or not) it reminds us to rethink our individual preferred prosecution styles and determine if at least some of the time we should do something a little different.

  • [Avatar for Pro Say]
    Pro Say
    January 28, 2023 07:06 pm

    Thanks Brian and commentators. Thought-provoking points, recommendations, and considerations all.

  • [Avatar for Anon]
    January 28, 2023 02:20 pm


    Thank you for an interesting article and a perspective steeped from the examiner point of view.

    That being said, it is that very point of view that I note as providing a bit of a foundation built upon sand.

    For example, you lead with a value judgment – one which has no bearing with either the vantage point of the applicant (based on cost or scope coverage), or one reflecting the history of claim counts (see, for example, (A shot from almost a decade ago – there was one much more recent, but I couldnto put my fingers on it), in which it should be noted that the 3/20 typical claim count is actually MORE than what historically was sought (second graph of the near-decade ago link).

    The bottom line for your foundation in error is that the statement of, “This led me to ponder why applicants are wasting the 13 other claims included with the standard filing fee with mirrored claims.” is simply that: a foundational error in asserting ‘value.’

    I would add that the notion of “by the time of allowance for enforceability reasons” quite misses the fact that if one starts at one point, and then must traverse to the point that you recognize, that the opportunity for induced prosecution history estoppel is necessarily implicated.

    That is not a good thing.

    (and also, your point of expected lower prosecution cost is actually the opposite – and RCEs would be increased, rather than reduced with your tactic)

    I will also point out that while you highlight a positive item of, :more avenues to explore patentability,” savvy practitioners already do this by way of continuation practice.

    Perhaps sadly, getting through this part of your article caused me to lose interest in digging further. Perhaps the second part of your article balances some of these points, but seeing as you set out with such a shaky foundation, I just lost interest in your perspective.

  • [Avatar for concerned]
    January 28, 2023 05:11 am

    I have seen many articles on this forum that suggests a “trick pony” to get a patent granted. In addition, Curious seems to have a few angles to get a patent granted, both of my statements are in reference to software applications.

    It still leads to the next question: You get the patent, but the courts take the granted patent away. I have seen no evidence on this forum of a person claiming victory over the courts, just victory over the examiner’s review process. Like when one parent says “yes” knowing the other parent will override the first parent and say “no.”

    The next question: Is an inventor better off never getting a patent granted or getting the patent and later getting the CAFC invalidation with considerable expense and frustration?

  • [Avatar for Max Drei]
    Max Drei
    January 27, 2023 12:55 pm

    Brian, suppose you are a corporate “bulk” filer that wants i) smooth and speedy prosecution to issue of ii) a commercially potent claim set, with iii) a value for money post-issue maintenance fee budget. That covers quite a few applicants, right.

    Such an applicant, internationally, is used to going to grant with independent apparatus, product, process claims and also perhaps independent claims to intermediates and uses, all in the same single issued patent. But this can happen only when all these independent claims can be accepted as being directed to different aspects of a single common inventive concept. A patent is for one invention only, right? When you see “mirror claims” is it not because, everywhere except the USA, they can all go through to issue in just one patent.

    Take the case of a concept XYZ. The apparatus claim is directed to x-ing means, Y-ing means etc while the method claim is to the steps of X-ing, Y-ing etc. In such a situation, is not the thing you call a “restriction requirement” i) invoked at the USPTO every time but ii) in every other Patent Office never invoked?

    Not only does the USPTO have a different search methodology than every other Patent Office, it also has a unique way of examining claims expressed in M+F form.

    As you say, the answer lies in writing two sets of claims, one for the USPTO exclusively, the other for everywhere else. Those “typical” claims sets you routinely see: I wonder, are they written for the USPTO or for RoW?

  • [Avatar for Breeze]
    January 27, 2023 10:05 am

    One reason for filing “mirror claims” in the manner you describe is to tell right off the bat if the examiner you are dealing with is a game playing, shenanigans loving knucklehead. When you file a case that only has, as you describe, “seven unique claims,” and the examiner is so incredibly lazy that they issue a restriction requirement anyway, complete with the usual “analysis” that doesn’t even come close to passing the straight face test, you have learned as much about that examiner as you need to know. No need to do a deep dive into the examiner’s “analytics.”

    And if the intent is to file continuations, elect the group you initially want, cancel the other groups, and file 13 or so new dependent claims in a preliminary amendment that makes the examiner search and examine 20 claims. All while enjoying safe harbor from OTDP for your divisionals.

    Another approach is to just file claims 19 and 20 as independent mirror claims of independent claim 1. You will probably still get a restriction, but see above.

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