Where the applicant claims the priority of an earlier application, a certified copy of that earlier application ("the priority document") must be filed with the receiving Office or the International Bureau within 16 months after the priority date. However, if the earlier application was filed with the receiving Office, the applicant may request that the receiving Office transmit a certified copy of the earlier application to the International Bureau. For that purpose, a check box is provided in Box No. VI of the PCT request form. 

If the EPO as receiving Office is requested to prepare and transmit a certified copy of an earlier application to the International Bureau, a fee is due (see point 2.2.032). However, no fee is due if the IB is requested to retrieve a priority document via DAS and it is available there (see point 2.15.003). In case no request via DAS is present, the EPO as receiving Office does not include, free of charge, a copy of an earlier application in the file of an international application – even if that earlier application was a European application or an international application filed with the EPO as receiving Office.

Where the earlier application was filed as a national application with a national office that participates in the Digital Access Service (DAS), the IB may be requested to obtain a certified copy of the earlier application from DAS. For that purpose a check box and a text field for the required access code are provided in Box No. VI of the PCT request form. Similarly, where the earlier application was a European patent application filed on or after 1 November 2018, the IB can be asked to obtain a certified copy via DAS since the EPO started to participate in DAS for Euro-direct filings as from that date. From 1 April 2019, it is also possible to request retrieval of a certified copy via DAS where the international application claims priority from a previous international application filed with the EPO as receiving Office. 

A priority document issued in paper form should also be submitted in that form to the EPO to ensure the validity of its certification. For that reason, it may not be filed by fax or using the EPO Web-Form Filing service. On the other hand, priority documents issued in electronic form are accepted only if they are digitally signed by the issuing authority and if that signature is also accepted by the EPO. At present, the Online Filing software and CMS support the submission of priority documents issued in electronic form (see point 2.2.032. Furthermore, during the international phase before the EPO as receiving Office, electronic priority documents can be submitted using ePCT.