How does the interpretation of contingent limitations differ between method and system claims?

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 interpretation of contingent limitations differs significantly between method and system claims. According to MPEP 2111.04, based on the Ex parte Schulhauser decision:

For method claims: “If the condition for performing a contingent step is not satisfied, the performance recited by the step need not be carried out in order for the claimed method to be performed.”

For system claims: “The broadest reasonable interpretation of a system claim having structure that performs a function, which only needs to occur if a condition precedent is met, still requires structure for performing the function should the condition occur.”

This means:

• In method claims, contingent steps may not be required if the condition is not met.
• In system claims, the structure for performing the contingent function must be present, regardless of whether the condition is met.

This distinction is crucial for patent attorneys and examiners when drafting and examining claims, as it affects the scope of the claims and the prior art that may be applied during examination.