Unity of invention

This article may need to be rewritten to comply with Wikipedia's quality standards. You can help. The talk page may contain suggestions. (July 2023)

In most patent laws, unity of invention is a formal administrative requirement that must be met for a patent application to proceed to grant. An issued patent can claim only one invention or a group of closely related inventions. The purpose of this requirement is administrative as well as financial. The requirement serves to preclude the possibility of filing one patent application for several inventions, while paying only one set of fees (filing fee, search fee, examination fee, renewal fees, and so on). Unity of invention also makes the classification of patent documents easier.

It is worth noting, that the WIPO and the EPO determine the unity of claims in a patent based on the presence of a common "special technical feature", which is usually equated with inventive step.^[1] On the other hand, the USPTO uses for its domestic applications a very different approach ("independent or distinct"), which is based on the fields of use for each claim,^[2] justifying this approach by a "burden on the examiner" to search different areas of technology. The patent offices in Japan and China, similarly to the USPTO, also demand splitting patent applications into multiple divisionals as a means of increasing the monetary revenue of the offices.^[3]

When a patent application is objected to on the ground of a lack of unity, it may be still considered for patent protection, unlike for example in the case where the invention is found to be lacking novelty. A divisional application can usually be filed for the second invention, and for the further inventions, if any. Alternatively, the applicant may counterargue that there is unity of invention.