In the international stage of PCT application, the applicant has two opportunities to make amendments:
1. Amendment according to Article 19 of the Patent Cooperation Treaty: After receiving the international search report, the applicant may submit an amendment to the patent claim to the International Bureau within the prescribed time limit. The modification period is within two months from the date of sending the international retrieval report or within 16 months from the priority date, whichever is later.
Two. Modification according to Article 34 of the Patent Cooperation Treaty: namely, modification that can be made after the initial examination procedure is started. From submitting the request for international preliminary examination to the examiner drafting the international preliminary report on patent, the applicant may propose amendments to the instructions, claims and drawings to China National Intellectual Property Administration, China within the prescribed time limit.
See/shewaizhishi/20170724108.html for details.