As a general rule, the examiner should not make any investigation as to the validity of a right to priority. However, the priority right assumes importance if prior art has to be taken into account which has been made available to the public within the meaning of Art. 54(2) on or after the priority date claimed and before the date of filing (e.g. an intermediate document, see G‑IV, 3) or if the content of the European patent application is totally or partially identical with the content of another European application within the meaning of Art. 54(3), such other application claiming a priority date within that period. In such cases, (i.e. cases where the art in question would be relevant if of earlier date) the examiner must investigate whether the priority date(s) claimed may be accorded to the appropriate parts of the application he is examining and should inform the applicant of the outcome and whether, in consequence, the particular prior art under consideration, e.g. the intermediate document, or the other European application forms part of the state of the art within the meaning of Art. 54. Also, in the case of possible conflict with another European application under Art. 54(3), it may be necessary in addition to allocate effective dates to the appropriate parts of that other application and to communicate this to the applicant analogously (see also G‑IV, 3). When the examiner needs to consider the question of priority date, he should bear in mind all the matters which are mentioned in F‑VI, 1.3 to F-VI 1.5 above.
If in case of a Euro-PCT application, where the EPO is acting as a designated or elected Office, the priority document is not on file, substantive examination may nevertheless be started. In such a case, without the priority document being on file, the application may even, where appropriate, be refused because the claimed subject-matter lacks novelty or inventive step, provided that the relevant state of the art is neither an intermediate document nor an Art. 54(3) application. However, no European patent may be granted until such time as the priority document is on file. In such a case, the applicant is informed that the decision to grant will not be taken as long as the priority document is missing.
If intermediate documents or Art. 54(3) applications exist and the patentability of the subject-matter claimed depends on the validity of the priority right, substantive examination cannot be finalised as long as the priority document is missing. Where the applicant has complied with Rule 17.1(a) PCT, Rule 17.1(b) PCT or Rule 17.1(b-bis) PCT, he may not be requested to file the priority document. The proceedings have to be stayed and the applicant is informed that, since the patentability of the subject-matter claimed depends on the validity of the priority right, substantive examination cannot be finalised as long as the priority document is not on file.