Can new matter be added to claims during ex parte reexamination?

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.

No, new matter cannot be added to claims during ex parte reexamination:

• The MPEP 2258 clearly states: “No amendment may introduce new matter into the disclosure of the patent.”
• This prohibition is based on 35 U.S.C. 305, which specifies that no proposed amended or new claim enlarging the scope of a claim of the patent will be permitted in a reexamination proceeding.
• Any amendment must be limited to clarification and restriction of the claims or the correction of errors or defects.

The purpose of this restriction is to maintain the integrity of the original patent disclosure and prevent the patent owner from gaining an unfair advantage by introducing new subject matter not originally disclosed. Amendments in reexamination must be supported by the original specification, drawings, or claims of the patent.