An international application may at the applicant's option be filed:

A third option exists for natural and legal persons who are nationals or residents of an EPC contracting state, since they may also file international applications with the EPO acting as a receiving Office. In such cases it is sufficient that at least one applicant is a national or resident of an EPC contracting state, regardless of whether he is for example mentioned in Box II of the PCT Request as applicant for the designation of the US or any other PCT contracting state only and, as the case may be, also as inventor. A person mentioned only as inventor does not qualify as an applicant. Hence, the nationality or residence of a person mentioned only as inventor is irrelevant for the purpose of filing an international application.

If there are two or more applicants, it is sufficient for at least one of the applicants to satisfy these requirements. For instance, if a national or resident of an EPC contracting state is mentioned in the PCT request form as inventor and applicant for the purposes of the United States only, the international application may be filed with the EPO as receiving Office regardless of the residence and nationality of the other applicant(s).