What is the “critical date” in relation to the public use and on-sale bars?

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.

The “critical date” is a crucial concept in patent law, particularly in relation to the public use and on-sale bars. According to MPEP 2133:

“The 1-year grace period in 35 U.S.C. 102(b) starts with the earliest of date of public use, sale, or publication.”

Key points about the critical date:

• It is exactly one year before the effective filing date of the patent application.
• Any public use or sale of the invention before this date can potentially bar patentability.
• The critical date serves as a cutoff point for assessing prior art and potential statutory bars.
• Inventors must be aware of this date to ensure they file their patent application within the grace period.

Understanding the critical date is essential for inventors and patent practitioners to avoid unintentional loss of patent rights due to public use or sales activities.