37 CFR § 1.412 - The United States Receiving Office.
(a) The United States Patent and Trademark Office is a Receiving Office only for applicants who are residents or nationals of the United States of America.
(b) The Patent and Trademark Office, when acting as a Receiving Office, will be identified by the full title “United States Receiving Office” or by the abbreviation “RO/US.”
(c) The major functions of the Receiving Office include:
(1) According of international filing dates to international applications meeting the requirements of PCT Art. 11(1), and PCT Rule 20;
(2) Assuring that international applications meet the standards for format and content of PCT Art. 14(1), PCT Rule 9, 26, 29.1, 37, 38, 91, and portions of PCT Rules 3 through 11;
(3) Collecting and, when required, transmitting fees due for processing international applications (PCT Rule 14, 15, 16);
(4) Transmitting the record and search copies to the International Bureau and International Searching Authority, respectively (PCT Rules 22 and 23); and
(5) Determining compliance with applicable requirements of part 5 of this chapter.
(6) Reviewing and, unless prescriptions concerning national security prevent the application from being so transmitted (PCT Rule 19.4), transmitting the international application to the International Bureau for processing in its capacity as a Receiving Office:
(i) Where the United States Receiving Office is not the competent Receiving Office under PCT Rule 19.1 or 19.2 and § 1.421(a); or
(ii) Where the international application is not in English but is in a language accepted under PCT Rule 12.1(a) by the International Bureau as a Receiving Office; or
(iii) Where there is agreement and authorization in accordance with PCT Rule 19.4(a)(iii).