Introduction:
What Is Double Patenting and Why Does It Matter in Patent Prosecution
What happens when you spend years creating your invention, file several patent applications protecting various elements of your invention, and finally receive an objection by the patent examiner that you are trying to patent the same invention twice? That is where double patenting becomes relevant.
Though usually considered a technical matter during the course of prosecuting patents, double patenting can have significant repercussions for the duration and effectiveness of a patent. The importance of comprehending this doctrine cannot be overstated, especially for inventors, companies, and patent professionals.
Why Is Double Patenting Necessary?
Patents offer a temporary monopoly on an invention in return for making its disclosure public. Nonetheless, the monopoly granted by a patent should not last beyond a certain period of time. Otherwise, allowing several patents on the same invention, or on similar inventions, would give patentees a chance to exceed their legal monopoly duration. This is prevented by a thorough analysis carried out by the relevant authorities, who verify whether patents cover similar inventions. This process is called double patenting.
Double patenting is commonly recognised in two kinds. The first one is statutory double patenting, where the claims filed in a new patent application are equal to those included in an existing patent. As a patent covers only one invention at a time, this situation should be avoided.
However, there is a second and much more prevalent form called non-statutory or obviousness-type double patenting (ODP), which occurs when the claims are not identical yet are so similar that one invention would be an obvious variant of the other. The issue here is less one of duplication and more about extending patent protection by making slight changes to claim language.
Why Patent Examiners Make Such Rejections?
Examiners are certainly not looking for similar wording when issuing these rejections; they simply want to stop inventors from filing for patents that cover the same subject matter in multiple patents.
Objections based on double patenting typically occur in cases of continuation patent applications, divisional patent applications, and very large patent families. This is because many such applications derive from the same invention. In such cases, double patenting rejections issued by the patent examiner simply indicate that the patent process is running smoothly and that patents are being granted within the required time period.
It should be noted that having double patenting rejections made against your patent application does not always mean that your invention is no good.
More Than Just a Procedural Hurdle
Although many applicants regard double patenting as merely procedural, there may be more at stake here than simple prosecution difficulties. If ignored, double patenting could become an issue that impacts the term of the patent, as well as its ability to be enforced.
Because double patenting rules are meant to prevent unwarranted extension of protection periods, any patent threatened by double patenting risks losing the extra term it might have had due to the overlap in protection.
Additionally, ignoring double patenting issues can leave the patent vulnerable in litigation proceedings, offering reasons for contesting validity or enforceability.
The Role of Terminal Disclaimers
Fortunately, double patenting rejections do not always spell disaster.
A terminal disclaimer may be filed as a response to double patenting rejections based on obviousness type. In this regard, the applicant pledges that the term of the second patent shall expire no later than the expiry of the first patent term. This also entails holding both patents by the same owner.
By preventing the existence of an extended monopoly, terminal disclaimers solve the problem at hand. Hence, this instrument has proved to be among the most frequently applied ones when addressing ODP claims.
Thus, Double patenting is far from being merely a technicality when it comes to patent applications. It embodies one of the basic ideas of patents, which is that inventors are to be rewarded for their innovation, yet they should not have several patents covering the same inventive concept. Regardless of whether double patenting deals with identical claims or their obvious variants, double patenting remains an essential part of patent practice. Those dealing with patent prosecution should be able to see the importance of this matter from the very beginning and to know how to deal with problems like a terminal disclaimer.
Author: Deeya. In case of any queries please contact/write back to us via email to [email protected] or at IIPRD.
References
- The Patent Term Adjustment Dilemma in an Obviousness-Type Double Patenting Analysis AIPLA (American Intellectual Property Law Association), 2023
- Obviousness-Type Double Patenting Rule Is Here to Stay Khushbu Shah, Fordham Intellectual Property, Media & Entertainment Law Journal, November 2022
- 2020 Patent Prosecution Tool Kit: Obviousness-Type Double Patenting Sterne, Kessler, Goldstein & Fox (2020, updated 2025)