Administrative Instructions under the Patent Cooperation Treaty
Language of Correspondence in Cases Not Covered by Rule 92.2
(a) The language of any letter from the applicant to the receiving Office shall be the same as the language of the international application to which such letter relates, provided that, where the international application is to be published in the language of a translation required under Rule 12.3(a) or 12.4(a), any letter shall be in such language. However, the receiving Office may expressly authorize the use of any other language.
(b) The language of any letter to the International Bureau shall be English where the language of the international application is English, and it shall be French where the language of the international application is French. Where the language of the international application is neither English nor French, the language of any letter to the International Bureau shall be English or French, provided that any copy, sent to the International Bureau as a notification addressed to it, of a Form sent to the applicant by the receiving Office, the International Searching Authority or the International Preliminary Examining Authority, does not require translation into English or French.