For EU instruments to have proper legal effect they need to be translated into all of 23 official languages spoke within the EU, i.e., Bulgarian, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Greek, Hungarian, Italian, Irish, Latvian, Lithuanian, Maltese, Polish, Portuguese, Romanian, Slovak, Slovene, Spanish and Swedish (as of 2007.) In addition, applications and correspondence with the European Commission must be accepted and is legally effective any one of the official languages.
However, in practice, since its inception, the European Commission has used two “Working Languages,” French and English, based on the view that most educated European professionals can communicate effectively in one or both of these languages. Recently Germany caused the European Commission to raise German to the status of a working language; anecdotally at least this has been somewhat of a flop, since German promises to enhance translation capacity to make this change effective have been poorly delivered on and because, for historical reasons, German was not widely taught in Europe between 1945 and the late 1970s limiting the number of professionals fluent in German as a second language. See London Agreement.