Lack of Unity in International Patent Applications: USPTO is not Unified in its Approach

The World international Patent Organization (WIPO) and most other major patent offices (for instance, the IP5 patent offices: European, Korean, Japanese, and Chinese) conform to similar standards for unity of invention except for the United States Patent and Trademark Office (USPTO), which enforces both the international standard (WIPO) and its own restriction practice. Among the IP5 offices and WIPO, unity of invention is present for a single invention or group of inventions so linked by a special technical feature to form a single general inventive concept.  In the USPTO, nationally filed applications have a different threshold for the requirement of a single invention for a single patent, known as restriction practice.  Restriction practice is employed when two or more independent and distinct invention are claimed and can be raised if, for instance, multiple classes or too numerous species are claimed so to impose an overly broad search requirement for the examiner.  To say the least, a restriction requirement can feel subjective from the perspective of the applicant.

A 2015 study by the Japan Intellectual Property Association highlights some of the roadblocks faced by international applications when entering the national stage in the USPTO in this regard.1  International patent applications are those filed through WIPO and subsequently go through an international search and are then provided a written opinion on the basis of the Paris Cooperation Treaty (PCT) rules. The study looks at a number of international applications that were found to have unity of invention during the international search and whether the applications were later found to lack unity of invention in the national phase.  In the Korean, Japanese, and Chinese offices, less than 5% of applications were later found to lack unity (the international search report and written opinion were conducted in the Japanese office), in the EPO about 9%, and in the USPTO 15-58% were later found to lack unity. The range in the USPTO was largely due to differing practices in different art classes with 58% of the applications in chemistry art classes being found to lack unity.  Interestingly, the average rate of restriction practice on nationally filed chemistry application is also close to 58%.  The study found proposes rationales for the high percentage of applications found to have lack of unity when entering the USPTO; many of which are related to the international prosecution history and form and content of the application itself.

Having a patent professional review your application before heading in to the national phase, especially the USPTO, can help you plan for possible outcomes because a rejection for lack of unity is not the end of patent prosecution; rather it can be the beginning of a diversified patent portfolio.


The First International Affairs Committee, Japan Intellectual Property Association, “Research and Study Concerning Differences in Determination of Unity of Invention among IP5 Offices”, Intellectual Property Management, Vol. 65, No. 8, 2015.

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