U.S. Patent Act
..Part IV. Patent Cooperation Treaty
....Chapt. 37. National Stage
(a) The required payment of the international fee and the handling fee, which amounts are specified in the Regulations, shall be paid in United States currency. The Patent and Trademark Office may also charge the following fees:
(1) A transmittal fee (see section 361(d) [35 USCS Sect. 361(d)]);
(2) A search fee (see section 361(d) [35 USCS Sect. 361(d)]);
(3) A supplemental search fee (to be paid when required);
(4) A national fee (see section 371(c) [35 USCS Sect. 371(c)]);
(5) A preliminary examination fee and any additional fees (see section 362(b)).
(6) Such other fees as established by the Commissioner.
(b) The amounts of fees specified in subsection (a) of this section, except the international fee, and the handling fee shall be prescribed by the Commissioner. He may refund any sum paid by mistake or in excess of the fees so specified, or if required under the treaty and the Regulations. The Commissioner may also refund any part of the search fee, the preliminary examination fee and any additional fees, where he determines such refund to be warranted.