The Difference Between a Patent Filing Date and Priority Date

By John DiGiacomo

In patent law, the patent “filing date” and the “priority date” are two important but different concepts. Often, the filing and priority dates are the same, but that is not always the case. Here is a quick rundown on the differences and why they matter.

Generally speaking, the filing date of a patent is the date on which a patent application is filed with the US Patent & Trademark Office (“USPTO”). By contrast, the priority date is the date from which the USPTO will evaluate the novelty — the newness — of the claimed invention. Novelty is one of several legal requirements for the granting of a patent. If an invention is not “new,” then it will not receive a patent from the USPTO. When a patent application is filed, the USPTO will begin an evaluation of the novelty of the invention by evaluating “prior art” that existed before the priority date. Prior art includes previously-filed patent applications and inventions/claims published in trade journals and other media. For these reasons, inventors generally want the earliest priority date because that makes it easier to demonstrate novelty.

As an example, assume an inventor files a patent application in June 2021 and claims a priority date of September 1, 2020. Assume also that, in December 2020, a competing inventor publishes materials and files a patent application covering the same invention in a foreign jurisdiction. In this example, if the USPTO uses September 1, 2020 as the priority date, then the prior art for this invention will NOT include the published materials and the foreign patent application from December 2020. This would likely enable our hypothetical inventor to demonstrate novelty.

An inventor may claim an earlier priority date under several circumstances. The most common circumstances are:

  • Full patent applications following an earlier provisional patent application
  • Continuation patent applications
  • US patent applications following or based on patent applications made in foreign jurisdictions

In the US, inventors can file provisional patent applications. One may think of a provisional patent application as a “short-form” filing which is, essentially, intended to preserve an early priority date. However, the full patent application must be filed within 12 months of the provisional application. The earlier priority date will be lost if the full application is not timely filed.

US patent law also allows continuation patents. One may think of these as “children” or “grand-children” of previously-filed patent applications based on the same patent claims. Continuation patent applications may claim the priority of the parent application.

Similarly, if a patent is filed in a foreign jurisdiction or under certain international treaties, the US application can claim, as the priority date, the filing date of the foreign patent application. As with provisional patent applications, the US patent application based on a foreign-jurisdiction application must be filed within 12 months. Otherwise, the earlier priority date will be lost.

Under some circumstances, more than one of these scenarios can apply. A continuation patent might be based on a parent application that has a priority date based on a provisional application. In that case, the new patent application may claim a priority date based on the date of the parent’s provisional application.

Contact Revision Legal

For more information or if you have an invention or design that you want to patent, contact the patent lawyers at Revision Legal at 231-714-0100.

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