1. Use of an official language 

Any party to oral proceedings before the EPO may use one of the other official languages of the EPO, on condition that they either inform the EPO at least one month before the scheduled date of the oral proceedings or make provision for interpreting into the language of the proceedings. In the former case, it is the EPO's responsibility to provide for interpretation at its own expense.

Parties must be clear about which official language they wish to use. They then have a right to both speak and hear that language, as long as the conditions of Rule 4 have been fulfilled. However, they do not have a right to speak in one language and hear a different language (see T 774/05).

The language of the proceedings as defined in Art. 14(3) cannot be changed. This means that any amendments to the application or patent have to be filed in the language of the proceedings (Rule 3(2)).

If all parties have indicated that they will use another official language, the division may depart from the language of the proceedings so as to manage without or with fewer interpreters (this question normally arises only in opposition proceedings). The parties' summonses are therefore accompanied by information which encourages them to agree how this can be achieved.

It may be possible to agree to limit the interpreting to "one-way", i.e. from one language into another but not the other way round. If a comment made in one language has clearly been misunderstood, the division may clarify it in another. Under no circumstances, however, can its members officially act as interpreters.