By-election

A by-election (occasionally also spelled bye-election, and known in the United States and the Philippines as a special election) is an election held to fill a political office that has become vacant between regularly scheduled elections.

Usually, a by-election occurs when the incumbent has died or resigned. It may also occur when the incumbent becomes ineligible to continue in office, for example because of a recall, ennoblement, a serious criminal conviction, failure to maintain a minimum attendance, bankruptcy or mental incapacity. By-elections have also been called as a result of a constituency election being invalidated by voting irregularities; see Oldham East and Saddleworth election petition.

Historically, members of some parliaments were required to seek re-election upon being appointed to a ministerial post. The subsequent by-elections were termed ministerial by-elections. These by-elections were usually a formality as they were normally, but not always, uncontested by opposition parties. The requirement for Members of Parliament (MPs) to resign their seats and re-offer upon being appointed to Cabinet was done away with as an anachronism in most Westminster systems by the mid-20th century.