What are C* designations in patent application classification?

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.

C* designations refer to Cooperative Patent Classification (CPC) symbols used to classify patent applications. These designations play a crucial role in the automated routing of applications to appropriate examiners.

According to MPEP 909.01(a):

“…the assigned examiner may submit a classification challenge to have a C* designation added and/or a C* designation removed.”

C* designations represent specific technical categories within the CPC system. They are used to accurately describe the subject matter of a patent application, which in turn helps in assigning the application to an examiner with the relevant expertise. If an examiner believes that a C* designation is incorrectly applied or missing, they can initiate a classification challenge to rectify the situation.