for "having performed his office," is a legal term used to describe a public official, court
, governing body, statute
, or other legal instrument that retains no legal authority because his or its duties and functions have been completed. The term is most commonly used by a higher court as a justification for vacating or overruling all or part of a lower court's opinion. For example, if a plaintiff in a United States federal court
, after filing a complaint but failing to serve it on the defendant, then files an amended complaint, the plaintiff cannot then serve the initial complaint on the defendant, because the filing of the amended complaint renders the original "functus officio."