Can a patent undergo multiple reexaminations?

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.

Yes, a patent can undergo multiple reexaminations. This is evident from the concept of “reexamination of a reexamination” discussed in MPEP § 2695. The section states:

“…a reexamination request filed on a patent for which a reexamination certificate has already issued, or a reexamination certificate issues on a prior reexamination, while the new reexamination is pending.”

This indicates that a patent can be subject to multiple rounds of reexamination, either sequentially or concurrently. Each reexamination may result in a new reexamination certificate, and subsequent reexaminations can be requested even after a certificate has been issued. This process allows for ongoing scrutiny of patent validity throughout its lifetime.