The issue of the admissible languages was one of the main reasons why the arose so many disputes and such a delay entering into force the UP regime and allowing the function of the UPC. The language of proceedings at the Central division of the Court of First Instance is the language in which the patent concerned was granted.
In the Nordic-Baltic Regional Division the language of the proceedings is English.
In the majority of Local Divisions, the claimant can choose the language of the proceedings among the official languages of the division’s location, or the ones declared before EPO by said division. Particularly in Austria and Germany the languages used in the proceedings are German and English. While after the start of the UPC the majority of the proceedings were initiated in Germany and (because Germany allowed English only shortly before start of the UPC) in German language, after 5 months it seems that English is going to become the more prominent language.
In the Regional and Local divisions there is the possibility to change the language of the proceedings to the language in which the patent was granted upon request. Last but not least, there is a special language regime concerning actions limited to the domicile of the defendant, in which the language of the defendant is used.
Regarding the Court of Appeal, the language of proceedings is in general the language that was used in proceedings before the Court of First Instance of that case.