How should patent examiners approach classification searching?

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.

Patent examiners should approach classification searching by considering both the claimed and disclosed inventions. The MPEP 904.02(a) states:

“A proper field of search normally includes the classification location(s) in which the claimed subject matter of an application would be properly classified at the time of the application’s classification or grant of a patent.”

Additionally, examiners should:

• Search all appropriate classifications, including those for disclosed features not claimed
• Consider both domestic and foreign patent documents
• Use various classification systems, including CPC, IPC, and USPC