According to Art. 14(4) EPC, natural or legal persons having their residence or principal place of business within the territory of a contracting state having a language other than English, French or German as an official language, and nationals of that state who are resident abroad, may file documents which have to be submitted within a given time limit in an official language of that state (these languages are sometimes referred to as "admissible non-EPO languages"). A translation in an official EPO language must also be filed (see R. 6(2) EPC). The scope of the fee reductions available in respect of documents filed in accordance with Art. 14(4) EPC has been limited with effect from 1 April 2014 (see in this chapter III.F.6.). For the language provisions with respect to the filing of the European patent application itself, see in this chapter III.F.1.

The board in T 149/85 (OJ 1986, 103) decided that it is inadmissible for a German opponent to file an opposition in Dutch even if represented by a Dutch patent attorney.

In T 1152/05 the notice of appeal was filed in Dutch by a company which had its principal place of business in the US and thus could not benefit from the provisions of Art. 14(4) EPC. A translation into French was filed on the same day. The notice of appeal was deemed not to have been filed. Following G 6/91 (OJ 1992, 491), if the translation was filed at the same time as the original, the EPO could not take it as the "official" notice of appeal and ignore the original as superfluous. See also T 41/09 and chapter III.A.3.2.1.