This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.
A species restriction in patent applications is a requirement for an applicant to elect a single disclosed species when there are multiple species claimed. According to MPEP 808.01(a), “Where there is no disclosure of a relationship between species (see MPEP § 806.04(b)), they are independent inventions. A requirement for restriction is permissible if there is a patentable difference between the species as claimed and there would be a serious search and/or examination burden on the examiner if restriction is not required.“
In other words, a species restriction is imposed when different species of an invention are claimed, and examining all of them would place an undue burden on the patent examiner.