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You are here: Home / Patent application process / Before filing a patent application / Inventor’s Notebook: Essential for Documenting Invention Development and Establishing Patent Priority

Inventor’s Notebook: Essential for Documenting Invention Development and Establishing Patent Priority

December 25, 2025 by James Yang

Under prior U.S. patent laws, the first-to-invent rule determined who would be awarded a patent, rather than the first-to-file rule, which is currently in effect. The first-to-invent rule awarded patents to the inventor who could demonstrate the earliest date of invention, not necessarily the first person to file an application with the Patent Office. This rule often required strong documentation of the invention’s development to establish invention dates.

However, as discussed below, under the America Invents Act (AIA), the United States now follows a first-inventor-to-file system. As a result, inventor’s notebooks are generally not very useful for newly filed patent applications that are subject to the AIA.

What Is an AIA Application (and What Is Not)

The America Invents Act (AIA) applies to any patent application that contains at least one claim with an effective filing date on or after March 16, 2013.

An AIA application is:

  • A patent application in which all claims have an effective filing date on or after March 16, 2013

  • Evaluated primarily based on filing date, not invention date

A non-AIA application is:

  • A patent application where all claims have an effective filing date before March 16, 2013

  • An application where invention dates, conception, and reduction to practice still matter

Importantly, once an application includes even a single claim with an effective filing date on or after March 16, 2013, the entire application becomes subject to the AIA.

Why Inventor’s Notebooks Are Largely Irrelevant Under the AIA

An AIA application looks to the filing date of the patent application to determine who is awarded a patent, not the date when the inventor conceived of the invention.  The inventor’s notebook is trying to establish the date of invention.  Put simply, the date of invention is irrelevant for AIA applications.

Case Illustration: Henkel Corp. v. Procter & Gamble Co.

In Henkel Corp. v. Procter & Gamble Co., 2008-1447 (Fed. Cir. 2009), Henkel challenged Procter & Gamble (P&G) in an interference proceeding before the Patent Office. Henkel claimed it had invented a dishwasher tablet with regions dissolving at different rates before P&G and should thus be awarded the patent. P&G, however, won the interference due to documentation showing that its inventor had appreciated the significance of the invention’s distinct dissolution rates before Henkel.

The court’s decision relied heavily on P&G’s written records, including a published report, which demonstrated that P&G’s inventor had developed and appreciated the invention’s unique qualities before Henkel. This case emphasizes the importance of well-documented invention progress to establish an earlier invention date.

The Role of an Inventor’s Notebook

An Inventor’s Notebook serves a critical function in recording the development of an invention, much like the documentation used by P&G. To support a strong claim to the invention’s priority:

  • In chemical inventions: Record the compounds used, including notes on how and why certain compounds were chosen for their unique properties.
  • In mechanical inventions: Include sketches of the invention, explaining the arrangement and function of key components.

Documenting these details establishes that the inventor understood and appreciated the invention’s unique aspects from an early stage, which can be vital in proving invention dates.

Key Takeaway

  • For AIA applications (most applications filed today): filing early matters far more than documenting invention dates

  • Inventor’s notebooks no longer determine priority

  • For non-AIA applications, inventor’s notebooks can still be critical

  • The safest strategy under current U.S. law is to file as early as possible.  Read my article on when to file.

If you need more information on documenting invention development or have questions about patent strategy, feel free to contact me at (949) 433-0900. As an experienced patent attorney serving Orange County, Irvine, Los Angeles, San Diego, and surrounding areas, I’m here to help you protect your inventions.

Author

James Yang is a patent attorney. For more than 16 years, James Yang has been representing clients to secure patent protection for their inventions and register trademarks to protect their brands. If you need help, call him at (949) 433-0900. Read More…

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