How are changes to the original patent shown in a reissue 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.

Changes to the original patent are shown in a specific manner in reissue patents:

• Material omitted from the original patent is enclosed in heavy brackets [ ]
• Material added by the reissue is printed in italics

As stated in the MPEP: “Matter enclosed in heavy brackets [ ] appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.” This heading is added by the Office of Data Management to clearly indicate the changes made in the reissue patent.