PCT International Search and Preliminary Examination Guidelines
8.08 Under Rule 91.1(g), a mistake shall not be rectified if:
(i) the mistake lies in the omission of one or more entire elements of the international application referred to in Article 3(2) (request, description, claims, drawings, or abstract) or one or more entire sheets of the international application;
(ii) the mistake is in the abstract;
(iii) the mistake is in an amendment under Article 19, unless the International Preliminary Examining Authority is competent to authorize the rectification because a demand for international preliminary examination has been made and has not been withdrawn and the date on which international preliminary examination is to start in accordance with Rule 69.1 has passed; or
(iv) the mistake is in a priority claim or in a notice correcting or adding a priority claim under Rule 26bis.1(a), where the rectification of the mistake would cause a change in the priority date.
Missing Elements or Sheets
8.09 However, it is noted that provisions for providing a missing element or sheet to the receiving Office are provided in Rules 20.3 to 20.8. An applicant may, under Rule 38.3, propose modifications to the abstract established by the International Searching Authority. Changes to the priority claim, other than a change in the priority date, may be made under either Rule 91 or Rule 26bis.1(a).
Correction of Priority Claims
8.10 Corrections or additions of priority claims that would affect the priority date may only be effected in accordance with Rule 26bis. However, where the applicant wishes to correct or add a priority claim but the time limit under Rule 26bis.1 has expired, the applicant may request the International Bureau to publish information concerning the matter. Any such request must be made prior to the expiration of 30 months from the priority date and is subject to the payment of a special fee.