What is C-STAR (C*) information in CPC classification and why is it important?

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-STAR (C*) information is a crucial aspect of CPC classification that identifies claimed concepts within a patent application. According to MPEP 905.03(a):

“A C-STAR (C*) is applied to an allocated symbol from the classification picture on an application when that symbol represents at least one concept that is claimed.”

C* designations are important because they:

• Highlight the specific aspects of the invention that are being claimed
• Help examiners and searchers focus on the core elements of the patent
• Must be applied to at least one CPC symbol in the classification picture

The MPEP further states:

“There is no limit to the number of the CPC symbols within the classification picture of an application that can be designated as a C*, but at least one CPC symbol must be designated as a C*.”

This ensures that the claimed subject matter is accurately represented in the classification, facilitating more precise prior art searches and examination.