A priority date is the earliest date on which an inventor can establish a date of invention. The inventor with the earlier priority date is awarded the patent. Typically, the priority date of a patent application is its filing date. If the patent application claims priority over other earlier filed patent applications, the priority date is the earliest filed provisional, nonprovisional or international patent application.
What’s the importance of a priority date?
The priority date is important because the inventor with the earliest priority date wins the race to the patent office and the rights to the patent. For example, where two people conceived the same invention, the inventor with the earlier priority date is awarded the patent. The patent application with the earlier filing date is prior art to the later filed patent application, and thus blocks the second inventor from obtaining a patent. The patent application with the earlier filing date, and thus priority does not have any prior art that would block from obtaining the patent.
How to claim a priority date?
The first step in claiming a priority date is to file a patent application describing how to make and use the invention (i.e., enablement requirement). When the patent application is filed, the inventor has claimed a priority date. It’s like a stake in the ground that establishes that at least as of this filing date, the invention belongs to the inventor.
Afterward, the inventor may file subsequent patent applications (i.e., continuation patent application, PCT application, national applications). These subsequent applications should claim priority back to the earliest filed patent application. To do so, you need to refer back to the earlier filed patent application and you must file the subsequent applications while the earlier filed patent application is still pending. Each circumstance is different so engage the help of a patent attorney to help you through the process.
Priority date versus filing date, grant date, pre-grant publication date
A priority date may be the same as a filing date. For example, the filing date of a provisional patent application is the priority date of the invention described in the provisional. However, when a corresponding nonprovisional patent application is filed claiming priority to the provisional patent application, the priority date of the nonprovisional patent application is the filing date of the provisional patent application, not the filing date of the nonprovisional patent application.
The grant date of a patent is the date the Patent Office granted the patent. The grant date is not a priority date. Another confusing date is the pre-grant publication date. This date is the date on which the patent application is published formally by the patent office. Typically, it occurs 18 months from the priority date.