What is the time limit for filing a U.S. application claiming foreign priority?

The U.S. nonprovisional application must generally be filed within 12 months of the filing date of the foreign application to claim priority. For design applications, this period is 6 months.

Specifically, 37 CFR 1.55(b) states:

“The nonprovisional application must be: (1) Filed not later than twelve months (six months in the case of a design application) after the date on which the foreign application was filed, subject to paragraph (c) of this section (a subsequent application); or (2) Entitled to claim the benefit under 35 U.S.C. 120, 121, 365(c), or 386(c) of a subsequent application that was filed within the period set forth in paragraph (b)(1) of this section.”

There are provisions to restore the right of priority if the subsequent application is filed within 2 months after the expiration of the priority period, if the delay was unintentional.