What is the difference between one-way and two-way distinctness in patent restriction requirements?

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.

In patent restriction requirements, the concepts of one-way and two-way distinctness are important for determining whether inventions are distinct:

• One-way distinctness: Generally sufficient for inventions in different statutory categories (e.g., a product and a process of making it).
• Two-way distinctness: Required for inventions in the same statutory category (e.g., two related products or two related processes).

MPEP 806.05 states: In applications claiming inventions in different statutory categories, only one-way distinctness is generally needed to support a restriction requirement. See MPEP § 806.05(c) (combination and subcombination) and § 806.05(j) (related products or related processes) for examples of when a two-way test is required for distinctness.

Two-way distinctness means that the inventions must be shown to be distinct from each other in both directions. For example, for related products, it must be shown that Product A could not anticipate or render obvious Product B, and vice versa.