2. Basis of the written opinion (WO‑ISA) 

Applicants cannot amend the application before the search report has been communicated to them. Consequently, the WO‑ISA will always relate to the application documents as originally filed or a translation thereof, and subject to the possibility of sequence listings being furnished later for the purposes of international search (see Rule 13ter.1). Furthermore, any reply filed by the applicant in response to an invitation for informal clarification (see GL/PCT‑EPO B‑VIII, 3.4) will also be taken into consideration when drawing up the written opinion.

Replacement pages or sheets, filed in response to an invitation by the receiving Office to correct defects in the international application, are deemed to be part of the international application "as originally filed". These sheets are identified with a stamp "SUBSTITUTE SHEET (RULE 26)" (see GL/PCT‑EPO H‑IV, 1). Also, replacement pages or sheets for rectification of obvious mistakes under Rule 91 (see GL/PCT‑EPO H‑IV, 2) are deemed to be part of the international application "as originally filed". These sheets are identified with "RECTIFIED SHEET (RULE 91.1)".

See GL/PCT‑EPO H‑IV, 2, for the procedure to follow if the rectified sheets contain added subject-matter.