The Best Mode Requirement: Not disclosing preferences in a patent application still a big mistake

Head_Idea_lightbulb_gearsThe best mode requirement is one of the three separate description requirements found in 35 U.S.C. 112(a); the other two are the enablement requirement and the written description requirement. In a nutshell, the best mode requirement says that the inventor must disclose any preferences relating to the claimed invention.

The best mode requirement still exists, although the America Invents Act (AIA) has largely removed any consequences for failing to disclose the inventor’s best mode, which means the current state of the law is at best a bit murky. But why would you ever want to file a patent application that does not disclose something that you prefer or regard as better? The goal of filing a patent application has to be to completely disclose your invention with as much detail and description as possible, paying particular attention to alternatives and variations. See also Tips & Tricks to Describe Your Invention in a Patent Application. So while you may be able to get away with not disclosing any preferences doing so would likely be a tragic mistake.

The best mode requirement historically created a statutory bargained-for-exchange between the patentee and the people. In exchange for the patent, which gives the patentee the right to exclude others from practicing the claimed invention for a certain time period, the public receives detailed knowledge of the invention. The written description requirement essentially requires the patent to define the metes and bounds of the invention, and the enablement requirement mandates that the patent explain how to both make and use the invention so that one of relevant skill in the art would be able to make and use the invention without undue experimentation. Best mode goes one step further. In addition to defining the metes and bounds in a way that explain how to make and use the invention it is necessary for the inventor to also disclose any preferences that pertain to the claimed invention.


In 1995 the United States Court of Appeals for the Federal Circuit succinctly explained the basics of the best mode requirement:

The sole purpose of the best mode requirement is to restrain inventors from applying for patents while at the same time concealing from the public preferred embodiments of their inventions, which they have in fact conceived. The best mode inquiry focuses on the inventor’s state of mind at the time he filed his application, raising a subjective factual question. The specificity of disclosure required to comply with the best mode requirement must be determined by the knowledge of facts within the possession of the inventor at the time of filing the application.

See Glaxo, Inc. v. Novopharm LTD., 52 F.3d 1043, 1050 (Fed. Cir. 1995).

In Glaxo the Federal Circuit went on to compare and distinguish the best mode requirement and the enablement requirement as follows:

Enablement looks to placing the subject matter of the claims generally in the possession of the public. Best mode looks to whether specific instrumentalities and techniques have been developed by the inventor and known to him at the time of filing as the best way of carrying out the invention.  The enablement requirement, thus, looks to the objective knowledge of one of ordinary skill in the art, while the best mode inquiry is a subjective, factual one, looking to the state of the mind of the inventor.

Thus, the best mode requirement was a safeguard against the desire on the part of some inventors (or their employers) to obtain patent protection without making as full a disclosure as required by the statute. Failure to disclose the best mode of the claimed invention was grounds for finding a claim at issue invalid.

With the enactment of the AIA the best mode requirement has largely been gutted, although it still remains a part of 35 U.S.C. 112(a). Ironically, although the best mode requirement remains in the statute and needs to be satisfied at the time the patent application is filed, the failure to disclose the best mode is no longer a basis on which any claim of an issued patent may be invalidated or otherwise unenforceable. This applies to all litigation proceedings commenced on or after September 16, 2011. Moreover, a previously filed application no longer needs to disclose the best mode in order to be entitled to claim priority. See 35 U.S.C. 119(e)(1) and 35 U.S.C. 120.

The question must then become – why would Congress keep the best mode requirement if they were going to render it useless insofar as determining validity and priority claims? Why not eliminate the best mode requirement from 35 USC 112? That is a good question for which there is no satisfactory answer.

The United States Patent and Trademark Office (USPTO) has noticed that while the lack of a best mode disclosure cannot be used to invalidate a claim or to prevent a claim of priority, the disclosure of the best mode remains one of the patentability requirements pursuant to 35 U.S.C. 112(a). For example, on September 20, 2011, just days after President Obama signed the AIA into law, a memorandum authored by Robert W. Bahr, who was then Senior Patent Counsel and Acting Associate Commissioner for Patent Examination Policy, was circulated to the Patent Examining Corps. In this memorandum Bahr explained:

Section 15 of the Leahy-Smith America Invents Act does not eliminate the requirement in 35 U.S.C. 112, first paragraph, for a disclosure of the best mode, but does amend 35 U.S.C. 282 (the provisions that sets forth defenses in a patent validity or infringement proceeding) to provide that the failure to disclose the best mode shall not be a basis on which any claim of a patent may be canceled or held invalid or otherwise unenforceable. As this change is applicable only in patent validity or infringement proceedings, it does not alter current patent examining practices set forth in MPEP 2165 for evaluation of an application for compliance with the best mode requirement of 35 U.S.C. 112.

Thus, 35 U.S.C. 112 still requires the disclosure of the best mode known to the inventor, so legally applicants are still required to disclose the best mode even though failure to do so will not invalidate an otherwise valid claim. Of course, one could legitimately ask the viability of the USPTO continuing to consider best mode given that it is a purely subjective test in the first part, which seeks to determine what the inventor actually preferred. The patent examiner would only in the most extremely rare cases ever be privy to information relating to the subjective preferences of inventors. Still, it is theoretically possible in that rare case, and if the patent examiner is made aware of preferences held by the inventor the claims implicated should not be granted. Thus, there is a distinction between issued patent claims and claims not yet issued when it comes to best mode.


Of course, much of this is really making a mountain out of a molehill. Playing fast and loose with the best mode requirement does not make a lot of sense, at least not for most inventors. Perhaps some inventors believe it to be advantageous to withhold information about preferences, but if you withhold information and do not include it in your patent application then it will not be a part of your invention. In other words, withholding the best mode not only calls into question whether you have satisfied the best mode requirement but will call into question whether your written description has fully described the complete invention.

For example, if you have a preference that relates to something that you are claiming and you do not disclose that preference you have violated the best mode requirement. Furthermore, your written description will not provide support for that which you did not include, so that preference is not a part of your invention, which means that you will not own the exclusive rights to that which you prefer.

Ask yourself this: If you have a preference why would you not want to own that preference? Most inventors certainly should want to disclose the best mode of their invention so that they can own the rights associated with what they prefer. Ordinarily it doesn’t make good sense to seek a patent on a version of the invention that is not optimal and allow the optimal version of the invention to remain unprotected. If anything you probably want to do it exactly the other way around.

Generally speaking, disclosing the best mode makes all the sense in the world for a variety of reasons. Being cute and trying to hide key preferences will ordinarily do nothing other than come back and bite you even today when there are really no consequences for violating the best mode requirement once you have an issued patent.


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Join the Discussion

6 comments so far.

  • [Avatar for Victor Sierra]
    Victor Sierra
    March 25, 2016 05:50 am

    From both of your statement I am at loss what is better full disclose preference or not. But I am quite agree with Gene that one should disclose its best mode preference. It would beneficial to inventor and invention. and it’s also show that It’s your invention, so you better describe its best mode preferences and claims.

  • [Avatar for Anon]
    February 7, 2016 12:09 pm

    Using “an example” simply misses the point that I presented Gene.

    Please actually address the point I put on the table, instead of wanting to talk about “an example.”

    Your statement is incorrect because – precisely – it is just far too encompassing. Will there be examples that including best mode is best for the client? No Doubt – and that is most definitely NOT what my point is about.

    Will there be examples (or times) that NOT including best mode is best for the client?


    And that is the point that I present.

    Further, it is an absolute red herring to talk about ethics charges against patent practitioners. Please. Any time that you are faced with such an obvious case of a practitioner knowingly concealing a best mode, there are at least a dozen other cases – much more on point here – that it will be impossible to make such an ethics charge.

    The only thing needed to burst your “bubble” is a single pin prick that does not fit into your “mandate.” There is mountain of such. Legal realism is not a pretty thing, but pretending otherwise is even less so.

  • [Avatar for Gene Quinn]
    Gene Quinn
    February 7, 2016 10:50 am


    You can believe I am wrong if you like, but good luck claiming the best mode when you have not disclosed the best mode.

    Let’s use a simple example. If the invention calls for the use of petroleum jelly and you prefer Vaseline(R), if you do not disclose your preference and yet were still able to get a patent the claim cannot be invalidated (as the article explains). But since you did not disclose Vaseline(R) you have no support for Vaseline(R) specifically. So if your preference mattered in order to overcome prior art, for example, you’d be out of luck because you have no support for the species and, therefore, no ability to narrow the claims by the inclusion of what you prefer. This is true because the disclosure of the genus does not as a matter of fact in all cases mean that you have disclosed the species.

    Sure, there are times that not disclosing things will seem advantageous to the client. And as long as they understand that they will likely not be able to insert the excluded preference into a claim and they are OK with that then there doesn’t seem to be a problem from the client’s perspective. In my experience, however, knowingly withholding subject matter from an application ends up not being particularly wise at the end of the road looking back when you have the benefit of hindsight. Given the many twists and turns of a patent application, the retroactive application of case law changes, the ever increasing specification requirements and how difficult it is to get valuable commercially relevant claims in some technologies, withholding a preference seems to me to be a real risk that in most cases is simply not worth taking.

    It seems to me that the decision not to disclose and to withhold is made when it is determined that the inventor has come up with something that would be far too difficult for anyone else to figure out on their own. That is as ridiculous as it sounds when dealing with an independent inventor, and it is as ridiculous as it sounds when dealing with a corporate inventor. A lot of hubris is involved when people think they are the only ones who can figure something out. History shows us that is rarely the case.

    Also, not that this article was about the patent practitioners responsibility, but remember that the Patent Office has said that OED does plan on enforcing the best mode requirement against patent practitioners. If it is learned that a best mode was known by the patent attorney and intentionally omitted, depending on who is in charge of OED at the moment that could very well lead to an ethics investigation.


  • [Avatar for Anon]
    February 6, 2016 06:51 pm

    You say one thing, Gene, then contradict yourself.

    To wit: “if you do not disclose it then it is not a part of your invention“:

    This is simply not a true statement on its face.

    The fact of the matter is that your invention (as written, described, and claimed) may be broader than the best mode and thus contain the best mode.

    Sorry Gene, but in this day and age (look too at the sui generis “right” of the Prior User Right), there are times and situations in which NOT disclosing things simply may be a better path for the client.

    This is not any indication of preference by me – this is just a little bit of legal realism.

  • [Avatar for Gene Quinn]
    Gene Quinn
    February 6, 2016 05:32 pm


    Nothing that I have written here at all conflates written description with best mode. Quite simply you have come to the wrong conclusion. In fact, I explain the differences between written description, enablement and best mode. Further, I did not suggest or say that a specific example is required.

    What I did say, however, is that if you have a preference you should disclose it because if you do not disclose it then it is not a part of your invention. Playing fast and loose with the best mode requirement and holding things back to keep them a secret will mean that you have not fully disclosed your invention and you will not be able to claim the preference. That is not generally a good idea.


  • [Avatar for Anon]
    February 6, 2016 04:24 pm

    I am not sure that the current state of the law allows you to draw the conclusion here that you have done.

    You have conflated the written description and the best mode.

    The MPEP discusses this (briefly) at:

    2165.01 II.

    There is no statutory requirement for the disclosure of a specific example — a patent specification is not intended nor required to be a production specification. In re Gay, 309 F.2d 768, 135 USPQ 311 (CCPA 1962).

    The absence of a specific working example is not necessarily evidence that the best mode has not been disclosed, nor is the presence of one evidence that it has. Best mode may be represented by a preferred range of conditions or group of reactants. In re Honn, 364 F.2d 454, 150 USPQ 652 (CCPA 1966).

    Oddly, the MPEP does discuss (again briefly) the conflation of the best mode with the other independent and distinct requirement of 112 at

    2165.02 Best Mode Requirement Compared to Enablement Requirement

    The best mode requirement is a separate and distinct requirement from the enablement requirement of 35 U.S.C. 112(a) or the first paragraph of pre-AIA 35 U.S.C. 112. In reNewton, 414 F.2d 1400, 163 USPQ 34 (CCPA 1969).

    So while this may be a minor distinction (and certainly NOT an example of best practices), the law itself should not be conflated as you have done here.