Once a U.S. filing deadline is past, filing of a patent application in the USPTO (at least one that can issue as a patent) is no longer possible. A variety of USPTO rules influence the U.S. filing deadline. If a PCT patent application has not previously been filed (a PCT Request submitted), the deadline is the earlier of (1) the filing date of the first priority patent application plus 12 months, (2) the date of the first public written disclosure (publication) plus 12 months, (3) the date of the first public use in the U.S. plus 12 months or (4) the date of the first offer to sell or sale in the U.S. plus 12 months. If a PCT Request has been submitted and a PCT Demand (under Chapter II of the PCT) has not been timely submitted, the deadline is the filing date of the first priority patent application plus 20 months. If a PCT Request has been submitted and a PCT Demand has been timely submitted, the deadline is the filing date of the first priority patent application plus 30 months. If the priority document is a provisional U.S. patent application, the special USPTO rule that allows filings to occur after weekends and holidays does not apply.
Law - U.S. Filing Deadline