What are the two subcombination-combination situations in patent applications?

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.

According to MPEP 806.05(c), there are two subcombination-combination situations in patent applications:

1. Subcombination essential to combination: The combination requires the details of the subcombination for patentability.
2. Subcombination not essential to combination: The combination does not require the details of the subcombination for patentability.

The MPEP states: “To support a requirement for restriction between combination and subcombination inventions, both two-way distinctness and reasons for insisting on restriction are necessary.” This means that examiners must consider both the relationship between the inventions and the practical reasons for requiring restriction.