This article is first in a two-part series focusing on various issues related to priority claims in U.S. patent applications. Part 1 is a general overview of how to make a proper priority claim, without addressing how to correct an improper priority claim, which will be examined in Part 2.
In general, for examination purposes at the U.S. Patent and Trademark Office (USPTO), a priority claim determines the priority date of a patent application. But why is that important? Because the priority date effectively determines what references can and cannot be asserted as prior art against a patent application during its examination. That is, the priority date draws a line in the sand for prior art, and this line cannot be crossed.