In an international application, all claims must relate to one invention only or to a group of inventions so linked as to form a single general inventive concept. If, during the international preliminary examination, the Examiner determines that unity of invention is lacking, he/she may examine all the claimed and previously searched inventions or he/she may invite the applicant to restrict the claims or pay additional fees. If the applicant is invited to restrict or pay, the applicant must respond within the time limit set by the Examiner. The time limit may not be shorter than one month or longer than two months from the date of mailing of the invitation.
Law - PCT Invitation to Restrict or Pay