What is a “substantial new question of patentability” in ex parte reexamination?

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 “substantial new question of patentability” is a key requirement for initiating an ex parte reexamination. As stated in MPEP 2209:

“The Office initially determines if ‘a substantial new question of patentability’ (35 U.S.C. 303(a)) is presented. If such a new question has been presented, reexamination will be ordered.“

This requirement ensures that the USPTO only conducts reexaminations when there are significant new issues to consider regarding the patentability of the claims. It typically involves new prior art or a new interpretation of previously considered prior art that raises questions about the validity of the patent that were not addressed in the original examination.