Editing Single transferable vote (section)

===By-elections===
As STV is a multi-member system and uses multi-member districts, filling a vacancy between elections can be problematic, and a variety of methods have been devised:
* The countback method is used in the [[Australian Capital Territory]], [[Tasmania]], Victoria, Malta, and [[Cambridge, Massachusetts]]. [[Casual vacancies]] can be filled by re-examining the ballot papers data from the previous election.<ref>{{Cite web |title=Do all countries have by-elections? Filling parliamentary vacancies around the world |url=https://www.electoral-reform.org.uk/do-all-countries-have-by-elections-filling-parliamentary-vacancies-around-the-world/ |access-date=23 June 2022 |website=www.electoral-reform.org.uk}}</ref> Officials determine the next-ranked candidate for those voters who supported the official whose seat was vacated.
* An alternative countback method is to appoint the candidate eliminated last (the most-popular unsuccessful candidate), who may represent a smaller minority than any of the candidates elected. Malta did this as a one-off for its [[2009 European Parliament election in Malta|2009 European elections]], to fill the prospective vacancy for the extra seat that arose from the [[Lisbon Treaty]].
* A head official or remaining members of the elected body appoint a new member to fulfill the vacancy. This may change the ideology of the seat.
* Hold a single-winner by-election (using instant-runoff voting); this allows each party to choose a new candidate and all voters across the wide district to participate. This is the method used in the Republic of Ireland in national elections and in Scotland's local elections. This likely produces a winner from the majority, which would be non-proportional if the seat was vacated by someone from a minority.
* The party of the vacant member nominates a successor, possibly subject to the approval of the voting population or the rest of the government. This is the method used in the Republic of Ireland in local elections.<ref>{{cite web |title=Local Elections Regulations, 1965. Section 87 |url=http://www.irishstatutebook.ie/eli/1965/si/128/made/en/print |website=S.I. No. 128/1965 – Local Elections Regulations, 1965.}}</ref>
* Officeholders create an ordered list of successors before leaving their seats. In the [[European Parliament]], a departing member from the Republic of Ireland or Northern Ireland is replaced with the top eligible name from a replacement list submitted by the candidate at the time of the original election. This method was also used in the [[Northern Ireland Assembly]] until 2009, when the practice was changed to allow political parties to nominate new MLAs in the event of vacancies. Independent MLAs may still draw up lists of potential replacements.<ref>{{cite press release |date=10 February 2009 |title=Change to the System for Filling Vacancies in the NI Assembly |url=http://www.nio.gov.uk/change-to-the-system-for-filling-vacancies-in-the-ni-assembly/media-detail.htm?newsID=15871 |publisher=Northern Ireland Office |access-date=5 October 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120307065031/http://www.nio.gov.uk/change-to-the-system-for-filling-vacancies-in-the-ni-assembly/media-detail.htm?newsID=15871 |archive-date=7 March 2012}}</ref>