5.13.4.Is it necessary to file a translation of the priority document? 

5.13.013Where the priority document is not in English, French or German, and the validity of the priority claim is relevant for determining whether the invention concerned is patentable, a translation in one of these languages must be submitted at the invitation of the EPO. If a translation is already available to the EPO, it will not issue an invitation. 

5.13.015Where the international application is a complete translation of the previous application, a declaration to that effect is sufficient and no invitation to file a translation will be issued (Form 1200, Section 7.3). This means that if the priority application is, for instance, a national application filed in Spanish, the applicant may declare that the international application filed in, for instance, English is a complete translation of the Spanish priority application. A translation from Spanish into an official language of the EPO is in that case not required. 

5.13.016A translation of the priority document may also be requested where the application was filed (in part) on the basis of incorporation by reference.