When do amendments become effective in a reexamined patent?

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.

Amendments proposed in a reexamination proceeding do not become immediately effective in the patent. The MPEP clearly states:

Although the Office actions will treat proposed amendments as though they have been entered, the proposed amendments will not be effective until the reexamination certificate is issued and published.

This means that while the amendments are considered during the reexamination process, they only become officially part of the patent when the reexamination is concluded and a certificate is issued under 35 U.S.C. 316. Patent owners should be aware of this delay in effectiveness when planning their strategy for reexamination proceedings.