A by-election is held to fill a vacancy in an electorate seat. A vacancy might arise, for example, through a member resigning their seat or dying in office.
As with a General Election, it is for the Prime Minister to determine the date of any by-election.
When a vacancy arises, the Speaker of the House of Representatives publishes a notice of the vacancy in the New Zealand Gazette. Within 21 days of that notice, the Governor-General must issue the writ directing the Chief Electoral Officer to conduct an election in the electorate. The writ sets out the key dates for the by-election: namely, the last day for the lodging of nominations of candidates, election day, and the last day for the return of the writ with the name of the elected candidate endorsed on its back.
For more information on the by-election timetable see sections 129-133, Electoral Act 1993.
A by-election has all the same features as a general election with a few exceptions. The differences are that it is an election for just one electorate, only registered electors of that electorate can vote, and there is no party vote. A by-election takes around the same time as a general election to run.
A by-election result can change the proportionality of Parliament that was determined at the preceding general election (for example, if a by-election is won by a candidate representing a different party from that of the member who vacated his or her seat).
A by-election is not required if –
(a)The vacancy arises within 6 months of the date on which Parliament would expire (on or after 10 April 2017); or
(b)The Prime Minister informs the House of Representatives in writing that a general election will be held within 6 months of the vacancy –
and 75% or more members of the House of Representatives resolve that a writ for a by-election not be issued.