Regulations under the PCT
Rule 52
Amendment of the Claims, the Description,
and the Drawings, before Designated Offices
(a) In any designated State in which processing or examination starts without special request, the applicant shall, if he so wishes, exercise the right under Article 28 within one month from the fulfillment of the requirements under Article 22, provided that, if the communication under Rule 47.1 has not been effected by the expiration of the time limit applicable under Article 22 , he shall exercise the said right not later than four months after such expiration date. In either case, the applicant may exercise the said right at any later time if so permitted by the national law of the said State.
(b) In any designated State in which the national law provides that examination starts only on special request, the time limit within or the time at which the applicant may exercise the right under Article 28 shall be the same as that provided by the national law for the filing of amendments in the case of the examination, on special request, of national applications, provided that such time limit shall not expire prior to, or such time shall not come before, the expiration of the time limit applicable under paragraph (a).