Court of Appeal, November 5, 2025, decision of the court of appeal, UPC_CoA_762/2024 and UPC_CoA_773/2024

If an (international) patent application is filed in a non-EPO language, the filing of the translation of the application into the language of the proceedings will define the substantive content of the application with regards to the requirements of inadmissible amendments under Art. 123 (2) EPC.

The translation filed by the applicant/patentee is presumed accurate, because the applicant/patentee has an interest in providing correct translations since the examination proceedings will be based on the translation of the application documents into the language of the proceedings. Parties (of proceedings as well as third parties) and the court can (prima facie) rely on the accuracy of the filed translation.

If the applicant/patentee considers the translation filed to be incorrect and wants to rely on a corrected version, the applicant/patentee needs to prove that the original translation is incorrect; it is insufficient to simply submit a corrected version of the document. A proof of an incorrect translation may be a declaration by a party expert. In the current decision: specifics of Korean language were considered important, hence a linguistic expert on Korean should have been named.