What is the significance of “substantially identical” claims in intervening rights?

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.

The concept of “substantially identical” claims is crucial in determining whether intervening rights apply in patent reexamination or reissue cases:

• Intervening rights only apply to claims that are not substantially identical to the original claims.
• If a claim is substantially identical to the original, it is treated as if it was in the original patent, and no intervening rights apply.
• Minor changes in wording that do not affect the scope of the claim typically result in substantially identical claims.

The MPEP 2293 states: “Claims which are ‘identical’ to original claims, or ‘substantially identical’ thereto, are not affected by reissue or reexamination.”

This distinction is important because it determines whether third parties can claim protection under intervening rights for actions taken before the reissue or reexamination. Only claims that have been substantively changed or newly added are subject to intervening rights.