1.1 General 

European patent applications can be filed in any language. However, if filed in a language other than an official EPO language (English, French and German), a translation into one of the official languages must be filed within two months of the date of filing (Rule 6(1)). Although filing in any language is in principle possible, there may be limitations due to the applicable national law for applications filed at a central industrial property office or the competent national authority under Art. 75(1)(b).

In the case of applications filed in "an admissible non‑EPO language" (see A‑VII, 3.2), a reduction of the filing fee is allowed for certain categories of applicants (see A‑X, 9.2.1 and A‑X, 9.2.2).

Filing a European patent application in a single language is not a requirement for according a filing date (Art. 90(3) in conjunction with Art. 14(2)). However, where an application is filed in more than one language, the EPO will invite the applicant to remedy the deficiency.