Where only a single patent application is involved, the priority date would obviously be the filing date of the sole application. If an applicant has filed a number of related patent applications, the priority date would be the filing date of the earliest patent filing that first disclosed the invention.
Essentially, a valid priority claim provides an earlier cut-off date for when a piece of prior art needs to have been disclosed to the public in order for it to be considered for assessing whether an invention is new and inventive.
The filing date is the date when a patent application is first filed at a patent office. The priority date, sometimes called the “effective filing date”, is the date used to establish the novelty and/or obviousness of a particular invention relative to other art.
What is a priority date and why does it is matter? A. Priority date refers to the earliest filing date in a family of patent applications. If the earliest-filed patent application for a particular invention was a provisional application, then the filing date of the provisional is your priority date.