How does constructive reduction to practice differ from actual 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.

Constructive reduction to practice differs from actual reduction to practice in several key ways:

• Filing vs. Physical Creation: Constructive reduction occurs when a patent application is filed, while actual reduction requires physically creating and testing the invention.
• Evidence Requirements: For constructive reduction, the patent application must meet the requirements of 35 U.S.C. 112(a), including enablement and written description. Actual reduction requires physical evidence of the invention working.
• Timing: Constructive reduction can be achieved earlier in the invention process, as it doesn’t require a working prototype.

As stated in MPEP 2138.05: “The filing of a patent application serves as conception and constructive reduction to practice of the subject matter described in the application. Thus the inventor need not provide evidence of either conception or actual reduction to practice when relying on the content of the patent application.”