1.3 Filing of documents subsequent to the application 

Documents subsequent to the international application may be filed with the EPO as receiving Office electronically or on paper (; see GL/PCT‑EPO A‑II, 1.2).

In the international phase, authorisations may not be filed with the EPO as receiving Office by fax or using the EPO Web-Form Filing service.

Priority documents issued in paper form which have to be certified by the issuing authority should also be submitted to the EPO in that form to ensure the validity of the certification. On the other hand, priority documents issued in electronic form may not be filed by fax, using the EPO Web-Form Filing service or using the EPO Contingency Upload Service. Priority documents may only be filed electronically using OLF or Online Filing 2.0, and provided they have been digitally signed by the issuing authority and the signature is accepted by the EPO; they may not be filed using the EPO Contingency Upload Service (see EPC Guidelines A‑III, 6.7.1). Electronic priority Priority documents may also be filed with the IB using ePCT.

If a document subsequent to the international application is filed by fax, there is no need to submit a confirmation copy unless the receiving Office invites the applicant to submit one (Form PCT/RO/141). It might do so particularly for substitute sheets under Rule 26 and sheets to be incorporated by reference under Rule 20.6. For such sheets, applicants are therefore advised to submit a confirmation copy on their own initiative directly after sending them by fax. If a confirmation copy is not submitted within the time limit prescribed in the invitation issued by the receiving Office, the document will be treated as not having been received (Form PCT/RO/149).