GA C5.13.2 5.13.2.

When is there an obligation to file the priority document with the EPO? 
If, during the international phase, the applicant did not submit a certified copy of the previous application (the "priority document") or indicate the file number of the application from which priority is claimed, they must provide either or both of them upon entry into the European phase. In some cases the EPO will be able to include a priority document in the file via electronic data exchange (see point 5.13.008).
A priority document may be filed electronically with the EPO using OLF or the CMS, provided it has been digitally signed by the issuing authority and the EPO can accept and verify the signature. The electronically filed priority document must be issued in a PDF format which complies with the Administrative Instructions under the PCT, Part 7 and Annex F. It cannot be filed by fax or using the EPO Web-Form Filing service. By way of example, the EPO accepts electronic priority documents issued and digitally signed by the USPTO and Brazil's National Institute of Industrial Property. 
Since 1 November 2018, for international applications entering the European phase before the EPO as designated Office, the EPO may retrieve priority documents via the Digital Access Service (DAS), provided the previous application was filed with another DAS-participating office. To make use of this service, applicants first ask the office with which the previous application was filed, the “office of first filing” (OFF), to make the priority document available via DAS, and then ask the EPO to retrieve a copy, by providing it with the access code assigned by the OFF. The access code can be communicated to the EPO using EPO Form 1013. DAS is free of charge for applicants. Currently 19 countries participate in it.[ 41 ]
PCT Newsletter 11/2018, 3 
Moreover, in the cases listed below, the EPO as designated/elected Office will include a copy of the priority application free of charge in the file of a Euro-PCT application even without having received a copy from the IB. The applicant will be informed of this inclusion unless the previous application is a European application or an international application filed with the EPO as receiving Office. This service is provided on condition that the applicant has informed the EPO of the application number and only if the priority application is:
a European patent application; 
an international application filed with the EPO as receiving Office; 
a Chinese patent or utility model application; 
a Japanese patent or utility model application; 
a Korean patent or utility model application; 
a United States provisional or non-provisional patent application. 
For a list of the participating offices, see

12 references found.

Click X to load a reference inside the current page, click on the title to open in a new page.

EPC Implementing Rules

EPO Guidelines - A Formalities Examination

EPO Guidelines - E General Procedural Matters

EPO Guide for Applicants, part II Int.

EPO Guide for Applicants, part II Int. - C The EPO as ISA and SISA

Offical Journal of the EPO