What is reduction to practice in patent law?

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.

Reduction to practice in patent law refers to the process of demonstrating that an invention actually works for its intended purpose. There are two types of reduction to practice:

• Actual reduction to practice: This occurs when an inventor physically creates and tests the invention.
• Constructive reduction to practice: This occurs when a patent application is filed that fully describes the invention.

As stated in MPEP 2138.05: “Reduction to practice may be an actual reduction or a constructive reduction to practice which occurs when a patent application on the claimed invention is filed.”