The U.S. Patent Office once offered a reasonably priced ($10.00) service by which, during the development of an invention, you could deposit in the Office a description of the invention in order to establish evidence of a specific date of invention, or at least a date of substantial conception. The program was intended to "provide a more credible form of evidence than that provided by the popular practice of mailing a disclosure to oneself or another person by registered mail." Because patent rights under U.S. law can be claimed by the first inventor in most cases, the Disclosure Document was a valuable tool for both the first inventor and the Office to have on file when a dispute over inventorship arose.

In order to make a valid claim of first inventorship, you have a duty to reduce the invention to practice^[note] within a reasonable time after its conception. For that reason, the Disclosure Document had a finite life of two years, after which it was destroyed. Where the purpose of granting patents is "To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries"¹, there is no benefit to society in allowing an inventor to sit on an invention in secret until the market is right for it, or until someone else does the hard work of reducing it to practice so that it can actually be made, done, or used.

The Disclosure Document Program was discontinued in 2007 in favor of the Provisional Patent Application. The provisional application anticipates a time, probably not far off, when U.S. patent law is brought in greater accord with patent law throughout most of the rest of the world, and patents are awarded not to the first inventor, but to the first to disclose an invention by applying for patent protection.

Briefly, the Provisional Patent Application has a finite effective term of only one year, shorter than the Disclosure Document was held. Before the expiration of that term you must file a proper patent application or lose the priority of your claim to the invention over others who may apply later. On filing a proper patent application within the term of the provisional application, however, the filing date of the provisional application can claimed as the effective priority date of the application.