Patent Drafting: Proving You’re in Possession of the Invention

The written description requirement, found in 35 U.S.C. 112(a), plays two important functions. First, it is used to define what constitutes the original filing (i.e., the disclosure present as of the date you file your patent application), which is then used to determine whether or not you are later during prosecution trying to sneak content into the application that is not supported by your original disclosure. You are not allowed to add new matter into a patent application, and what is new matter is determined based on whether it was present at the time of filing. If it was present in the original disclosure at the time of filing it is not new matter and the amendment can be entered. If the material was not present at the time of filing it would constitute new matter and the amendment could not be entered.

The second aspect of the written description requirement, and the focus of this article, relates to proving that the applicant is actually in possession of the invention.

The purpose of the written description requirement is broader than to merely explain how to make and use the invention, which is the subject of the enablement requirement. Rather, to satisfy the written description requirement the applicant must also convey with reasonable clarity to those skilled in the art that, as of the filing date sought, he or she was in possession of the invention. Vas-Cath, Inc. v. Mahurkar, 935 F.2d 1555, 1563-64 (Fed. Cir. 1991). For the purposes of the written description inquiry the invention is whatever is being claimed. Id.


The written description requirement as articulated in Section 112(a) states: “[t]he specification shall contain a written description of the invention… in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains… to make and use the same…” This requirement ensures “that the inventor actually invented the invention claimed.” Ariad Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc). To show invention, a patentee must convey in its disclosure that it “had possession of the claimed subject matter as of the filing date.” Id. at 1350. Demonstrating possession “requires a precise definition” of the invention. Id.

The question about whether the written description requirement has been satisfied, if litigated, will be a question of fact. Amgen, Inc. v. Sanofi, Aventisub LLC, No. 2017-1480 (Fed. Cir. 2017). Whether the written description is sufficient will be judged based on the state of the art as of the priority date. Id. Evidence relating to the state of the art pertaining to the invention from after the priority date is simply not relevant to the written description inquiry. Id.

To provide this “precise definition” the applicant must describe the invention with as much detail as possible. While examples are not required, examples can be extremely helpful for most types of inventions.

While the written description is just that – written – having multiple drawings that show the invention and various aspects of the invention from a variety of viewpoints can be extremely helpful. This is because every figure should be described with at lease one paragraph of text, frequently more. For information about how to leverage drawings in a written description see Working with Patent Illustrations to Create a Complete Disclosure.

Explain as Much as Possible

When attempting to satisfy the written description requirement, and in order to file a solid, omnibus specification that can be used as a foundation for a patent family, it is necessary to explain as much as possible. This is critical because the first filing must be a complete and thorough description of the invention, including all the various alternatives and permutations that can be envisioned. This is necessary because while the format of an application can be changed, information cannot be added while still keeping the benefit of the original filing date. For this reason the specification should not only mention the minimum distinguishing features necessary to overcome the prior art that is known, but instead the specification should also discuss specifics, not only to expand your disclosure, but to make sure that at least one (or hopefully more) of the embodiments disclosed will ultimately be patentable.  This is true because you can always expect an examiner to come up with prior art that you never thought existed because patent applications remain hidden from the public for at least 18 months after they are filed. That means more prior art will be used against your application when examined than the applicant could possibly know about at the time of filing.

Beware Generic Descriptions

General descriptions can be helpful, but a general description leaves open a lot of possibilities. Because it leaves open a lot of possibilities it is both good and bad. Being generic is good to create a broad scope, but only being generic is bad because the specifics are not described. While describing the generic may implicitly disclose the specific, this could run afoul of the written description requirement, which requires the invention to be particularly described so that the reader will understand the scope of what has been invented by the inventor. The written description requirement is to ensure that a patent is limited to what the inventor has specifically invented; stated in patent terms the written description requirement is used (in part) to ensure that the inventor is in possession of the invention. In order to demonstrate possession of an invention it is important to demonstrate possession of both generic and specific embodiments. So, there is no substitute for describing the specifics of use and structure.

Only describing the generic and refusing to describe specifics associated with an invention is a terrible mistake. While there are many reasons for this, a generic description will be much easier to find prior art against, while specific descriptions provide important nuance to distinguish an invention over the prior art. Further, today patent eligibility is a real concern for some types of innovations, and generic descriptions that lack specificity can and do create insurmountable problems with respect to 35 U.S.C. 101, which is have become quite related to 112 disclosure issues over the last several years.


Articulate the Boundaries

It is very important that a patent application completely define the invention with particularity, as specifically required in the statute. Merely saying that different versions can exist is a first step, but without more the written description does not teach what the differences are or can be. The written description requirement essentially requires applicants to define the invention so that the person of skill in the art will be able to appreciate exactly the boundaries of what has been invented. When other, undefined and unexplained variations can be made be interesting, but does not define the boundaries in a bright line way sufficient to satisfy the written description requirements. There is nothing per se wrong with including catchall statements in a patent application, but it is important to understand that they provide little, if any, benefit. It is critical to take the next step beyond saying additional versions of the invention can exist and explain what those additional versions are, what variations exist, how they may be structured and used. Pay particular attention to disclosing alternative features and structures using permissive (not mandatory) language. Always describe everything with as much detail as possible, focusing on the tangible elements and characteristics wherever possible.

Additional Information

For more tutorial information please see Invention to Patent 101: Everything You Need to Know. For more information specifically on patent application drafting please see:


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

3 comments so far.

  • [Avatar for Lost In Norway]
    Lost In Norway
    November 6, 2017 03:22 am

    Good article, Gene. Even after having felt like I live 102(a), I never really thought about it as proof of possession of the invention. I have to admit to feeling a bit silly about this fact.

  • [Avatar for Anon]
    November 5, 2017 01:27 pm

    Mr. Morgan raises an excellent point, and one that can be expanded to a fairly wide degree:

    Avoid patent profanity.

    Unfortunately, the judicial branch has created many traps for the unwary with instances of patent profanity (of which, the limiting of a patent holder’s rights because of particular phrases used is but one example).

  • [Avatar for Paul F. Morgan]
    Paul F. Morgan
    November 5, 2017 08:17 am

    Good article.
    But avoid using the words “the invention is…” to avoid potentially inadvertently limiting the scope of the invention.