Administrative Instructions under the Patent Cooperation Treaty
Section 321
Application of Moneys Received by the Receiving Office in Certain Cases
(a) The receiving Office shall, to the extent that it has received instructions from the applicant as to the fees to which it shall apply moneys received by it from the applicant, apply those moneys accordingly.
(b) Where the receiving Office receives moneys from the applicant which, together with any other moneys so received, are not sufficient to cover in full the transmittal fee (if any), the international filing fee and the search fee (if any), the receiving Office shall, to the extent that it has not received instructions from the applicant as to the fees to which it shall apply the moneys which are available for the purpose, apply those moneys in payment, successively, of the fees set out below to the extent that they are due and unpaid and in the order in which they appear below: