What is the difference between actual reduction to practice and constructive reduction to practice?

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.

Actual reduction to practice and constructive reduction to practice are two distinct concepts in patent law:

• Actual reduction to practice occurs when an inventor physically creates the invention and demonstrates that it works for its intended purpose. This involves building and testing a working prototype.
• Constructive reduction to practice is achieved when an inventor files a patent application that adequately describes the invention in sufficient detail to enable a person skilled in the art to make and use the invention.

The MPEP 2138.05 states: “In Hyatt v. Boone, 146 F.3d 1348, 1352, 47 USPQ2d 1128, 1130 (Fed. Cir. 1998), the court held that ‘the filing of a patent application serves as conception and constructive reduction to practice of the subject matter described in the application.’”