Was there a year 0?

Cassini gave the following reasons for using a year 0:
Fred Espanak of NASA lists 50 phases of the moon within year 0, showing that it is a full year, not an instant in time. Jean Meeus gives the following explanation:
Although he used the usual French terms "avant J.-C." (before Jesus Christ) and "après J.-C." (after Jesus Christ) to label years elsewhere in his book, the Byzantine historian Venance Grumel used negative years (identified by a minus sign, −) to label BC years and unsigned positive years to label AD years in a table. He did so possibly to save space and put no year 0 between them.

Astronomical year numbering

Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0; the years before that are designated with negative numbers and the years after that are designated with positive numbers. Astronomers use the Julian calendar for years before 1582, including the year 0, and the Gregorian calendar for years after 1582, as exemplified by Jacques Cassini (1740), Simon Newcomb (1898) and Fred Espenak (2007).

The prefix AD and the suffixes CE, BC or BCE (Common Era, Before Christ or Before Common Era) are dropped. The year 1 BC/BCE is numbered 0, the year 2 BC is numbered −1, and in general the year "n" BC/BCE is numbered "−("n" − 1)" (a negative number equal to 1 − "n"). The numbers of AD/CE years are not changed and are written with either no sign or a positive sign; thus in general "n" AD/CE is simply "n" or +"n". For normal calculation a number zero is often needed, here most notably when calculating the number of years in a period that spans the epoch; the end years need only be subtracted from each other.

The system is so named due to its use in astronomy. Few other disciplines outside history deal with the time before year 1, some exceptions being dendrochronology, archaeology and geology, the latter two of which use 'years before the present'. Although the absolute numerical values of astronomical and historical years only differ by one before year 1, this difference is critical when calculating astronomical events like eclipses or planetary conjunctions to determine when historical events which mention them occurred.

In his Rudolphine Tables (1627), Johannes Kepler used a prototype of year zero which he labeled "Christi" (Christ's) between years labeled "Ante Christum" (Before Christ) and "Post Christum" (After Christ) on the mean motion tables for the Sun, Moon, Saturn, Jupiter, Mars, Venus and Mercury. In 1702, the French astronomer Philippe de la Hire used a year he labeled at the end of years labeled "ante Christum" (BC), and immediately before years labeled "post Christum" (AD) on the mean motion pages in his "Tabulæ Astronomicæ", thus adding the designation "0" to Kepler's "Christi". Finally, in 1740 the French astronomer Jacques Cassini, who is traditionally credited with the invention of year zero, completed the transition in his "Tables astronomiques", simply labeling this year "0", which he placed at the end of Julian years labeled "avant Jesus-Christ" (before Jesus Christ or BC), and immediately before Julian years labeled "après Jesus-Christ" (after Jesus Christ or AD).

Version 1.0 of the XML Schema language, often used to describe data interchanged between computers in XML, includes built-in primitive datatypes date and dateTime. Although these are defined in terms of ISO 8601 which uses the proleptic Gregorian calendar and therefore should include a year 0, the XML Schema specification states that there is no year zero. Version 1.1 of the defining recommendation realigned the specification with ISO 8601 by including a year zero, despite the problems arising from the lack of backward compatibility.

Year zero does not exist in the anno Domini system usually used to number years in the Gregorian calendar and in its predecessor, the Julian calendar. In this system, the year is followed by. However, there is a year zero in astronomical year numbering (where it coincides with the Julian year ) and in ISO 8601:2004 (where it coincides with the Gregorian year ) as well as in all Buddhist and Hindu calendars.

Year zero

The "Anno Domini" era was introduced in 525 by Scythian monk Dionysius Exiguus (c. 470–c. 544), who used it to identify the years on his Easter table. He introduced the new era to avoid using the "Diocletian era", based on the accession of Roman Emperor Diocletian, as he did not wish to continue the memory of a persecutor of Christians. In the preface to his Easter table, Dionysius stated that the "present year" was "the consulship of Probus Junior [Flavius Anicius Probus Iunior]" which was also 525 years "since the incarnation of our Lord Jesus Christ". How he arrived at that number is unknown.

Dionysius did not use AD years to date any historical event. This began with the English cleric Bede (c. 672–735), who used AD years in his "Historia ecclesiastica gentis Anglorum" (731), popularizing the era. Bede also used a term similar to the English before Christ once, but that practice did not catch on until very much later. Bede did not sequentially number days of the month, weeks of the year, or months of the year. However, he did number many of the days of the week using a counting origin of one in Ecclesiastical Latin. Previous Christian histories used "anno mundi" ("in the year of the world") beginning on the first day of creation, or "anno Adami" ("in the year of Adam") beginning at the creation of Adam five days later (the sixth day of creation according to the Genesis creation narrative), used by Africanus, or "anno Abrahami" ("in the year of Abraham") beginning 3,412 years after Creation according to the Septuagint, used by Eusebius of Caesarea, all of which assigned "one" to the year beginning at Creation, or the creation of Adam, or the birth of Abraham, respectively. Bede continued this earlier tradition relative to the AD era.

In chapter II of book I of "Ecclesiastical history", Bede stated that Julius Caesar invaded Britain "in the year 693 after the building of Rome, but the sixtieth year before the incarnation of our Lord", while stating in chapter III, "in the year of Rome 798, Claudius" also invaded Britain and "within a very few days [...] concluded the war in [...] the fortysixth [year] from the incarnation of our Lord". Although both dates are wrong, they are sufficient to conclude that Bede did not include a year zero between BC and AD: 798 − 693 + 1 (because the years are inclusive) = 106, but 60 + 46 = 106, which leaves no room for a year zero. The modern English term "before Christ" (BC) is only a rough equivalent, "not" a direct translation, of Bede's Latin phrase "ante incarnationis dominicae tempus" ("before the time of the lord's incarnation"), which was itself never abbreviated. Bede's singular use of 'BC' continued to be used sporadically throughout the Middle Ages.

Neither the concept nor a symbol for zero existed in the system of Roman numerals. The Babylonian system of the BC era had used the idea of "nothingness" without considering it a number, and the Romans enumerated in much the same way. Wherever a modern zero would have been used, Bede and Dionysius Exiguus did use Latin number words, or the word "nulla" (meaning "nothing") alongside Roman numerals. Zero was invented in India in the sixth century, and was either transferred or reinvented by the Arabs by about the eighth century. The Arabic numeral for zero (0) did not enter Europe until the thirteenth century. Even then, it was known only to very few, and only entered widespread use in Europe by the seventeenth century.

The "anno Domini" nomenclature was not widely used in Western Europe until the 9th century, and the to historical year was not uniform throughout Western Europe until 1752. The first extensive use (hundreds of times) of 'BC' occurred in "Fasciculus Temporum" by Werner Rolevinck in 1474, alongside years of the world ("anno mundi"). The terms "anno Domini", "Dionysian era", "Christian era", "vulgar era", and "common era" were used interchangeably between the Renaissance and the 19th century, at least in Latin. But "vulgar era" was suppressed in English at the beginning of the 20th century after "vulgar" acquired the meaning of "offensively coarse", replacing its original meaning of "common" or "ordinary". Consequently, historians regard all these eras as equal.

Historians have never included a year zero. This means that between, for example, and, there are 999 years: 500 years BC, and 499 years AD preceding 500. In common usage "anno Domini" 1 is preceded by the year 1 BC, without an intervening year zero. Neither the choice of calendar system (whether Julian or Gregorian) nor the era ("Anno Domini" or Common Era) determines whether a year zero will be used. If writers do not use the convention of their group (historians or astronomers), they must explicitly state whether they include a year 0 in their count of years, otherwise their historical dates will be misunderstood.

In astronomy, for the year AD 1 and later it is common to assign the same numbers as the Anno Domini notation, which in turn is numerically equivalent to the Common Era notation. But the discontinuity between 1 AD and 1 BC makes it cumbersome to compare ancient and modern dates. So the year before 1 AD is designated 0, the year before 0 is −1, and so on.

The letters "AD", "BC", "CE, or "BCE" are omitted. So 1 BC in historical notation is equivalent to 0 in astronomical notation, 2 BC is equivalent to −1, etc. Sometimes positive years are preceded by the + sign. This year numbering notation was introduced by the astronomer Jacques Cassini in 1740.

In 1627, the German astronomer Johannes Kepler first used an astronomical year which was to become year zero in his "Rudolphine Tables". He labeled the year "Christi" and inserted it between years labeled "Ante Christum" (BC) and "Post Christum" (AD) on the mean motion pages of the Sun, Moon, and planets. Then in 1702 the French astronomer Philippe de la Hire used a year he labeled at the end of years labeled "ante Christum" (BC), immediately before years labeled "post Christum" (AD) on the mean motion pages in his "Tabulæ Astronomicæ", thus adding the designation "0" to Kepler's "Christi". Finally, in 1740 the French astronomer Jacques Cassini, who is traditionally credited with the invention of year zero, completed the transition in his "Tables astronomiques", simply labeling this year "0", which he placed at the end of years labeled "avant Jesus-Christ" (BC), immediately before years labeled "après Jesus-Christ" (AD).

ISO 8601:2004 (and previously ISO 8601:2000, but not ISO 8601:1988) explicitly uses astronomical year numbering in its date reference systems. Because it also specifies the use of the proleptic Gregorian calendar for all years before 1582, some readers incorrectly assume that a year zero is also included in that proleptic calendar, but it is not used with the BC/AD era. The "basic" format for year 0 is the four-digit form 0000, which equals the historical year 1 BC. Several "expanded" formats are possible: −0000 and +0000, as well as five- and six-digit versions. Earlier years are also negative four-, five- or six-digit years, which have an absolute value one less than the equivalent BC year, hence -0001 = 2 BC. Because only ISO 646 (7-bit ASCII) characters are allowed by ISO 8601, the minus sign is represented by a hyphen-minus.

All eras used with Hindu and Buddhist calendars, such as the Saka era or the Kali Yuga, begin with the year 0. All these calendars use elapsed, expired, or complete years, in contrast with most other calendars which use current years. A complete year had not yet elapsed for any date in the initial year of the epoch, thus the number 1 cannot be used. Instead, during the first year the indication of 0 years (elapsed) is given in order to show that the epoch is less than 1 year old. This is similar to the Western method of stating a person's age – people do not reach age one until one year has elapsed since birth (but their age during the year beginning at birth is specified in months or fractional years, not as age zero). However, if ages were specified in years and months, such a person would be said to be, for example, 0 years and 6 months or 0.5 years old. This is analogous to the way time is shown on a 24-hour clock: during the first hour of a day, the time elapsed is 0 hours, "n" minutes.

Year zero

Year zero


How many members are in the Senate of Australia?

Section 24 of the Constitution of Australia requires that the total number of members of the Australian House of Representatives shall be "as nearly as practicable" twice as many as the number of members of the Australian Senate. There is presently a total of 76 senators: 12 senators from each of the six states and two from each of the two autonomous internal territories (the Australian Capital Territory and the Northern Territory). There are 150 members of the Australian House of Representatives.

Redistribution (Australia)

In Australia, a redistribution is the process of redrawing the boundaries of electoral divisions of the House of Representatives, a process that in the United States is called redistricting. The Australian Electoral Commission, an independent statutory authority, completely independent of political considerations, oversees the redistribution process, taking into account many factors, including the one vote, one value principle. Members of Parliament and political parties may make submissions to the Commission on proposed new boundaries, but any interference with the Commission's deliberations would be a serious offence. Each State and Territory has its own Electoral Commission which follows similar, but not identical processes and principles for the determining electoral boundaries and conducting elections within their jurisdiction.

Section 24 of the Constitution of Australia specifies that the number of members of the House of Representatives in each State is to be calculated by reference to their population, with a minimum of five members guaranteed for each "original" State. Each Territory is granted a minimum of two members. After the number of members for each State and Territory is determined, in a process called apportionment or determination, the State and Territory is divided into that number of electoral divisions.

The "Commonwealth Electoral Act 1918" requires that all electoral divisions within a state or territory have approximately an equal numbers of enrolled voters. The "Commonwealth Electoral Act (No. 2) 1973", passed at the joint sitting of Parliament, reduced the allowable quota variation of the number of electors in each division from 20% to 10%. Demographic changes both between States and within States requires a regular review of division boundaries to ensure that the number of electors in each division within a State or Territory does not deviate by more than 10% (plus or minus) from the state or territory average. A redistribution (sometimes called redrawing or "revision") of the geographic boundaries of divisions takes place at least once every seven years. When the Commission determines that population shifts within a state have caused some seats to have too many or too few voters, a redistribution is called and new boundaries are drawn up. Redistributions are also held when the Commission determines (following a formula laid down in the "Electoral Act") that the distribution of seats among the states and territories must be changed because some states are growing faster than others.

For example, in 2003, a review resulted in South Australia losing one seat, and Queensland gaining a seat. Redistributions were held in Victoria, Queensland and South Australia. Victoria kept the same number of seats, but one seat was abolished and one new seat created.

New, redistributed boundaries apply only to general elections held after the redistribution process has been completed, so that should a by-election be called before a general election, that by-election will be conducted on the basis of the previous electoral boundaries.

The total number of members of the Australian House of Representatives, and consequently electorates, has increased from time to time. Every time there is an increase in the number of members, a redistribution is required to be undertaken, except in Tasmania which has always had the constitutional minimum number of five members. At the first federal election there were 65 members of the House of Representatives. In 1949, the number was increased from 74 to 121 (excluding the Australian Capital Territory and the Northern Territory), and in 1984 it was increased from 125 to 148.

Section 24 of the Constitution requires that electorates be apportioned among the States in proportion to their respective populations; provided that each original State has at least 5 members in the House of Representatives.

Section 29 of the Constitution forbids electorate boundaries from crossing state lines, and the "Commonwealth Electoral Act 1918" sets out further requirements. The population in each State is officially communicated to the Australian Electoral Commission (AEC) by the Australian Bureau of Statistics, which estimates the population about a year after each election.

The AEC calculates the number of members/divisions for a State as follows:

The entitlement of each state is rounded to the nearest whole number. However, each Original State is entitled to a minimum of 5 members, a provision that gives Tasmania higher representation than its population would justify. The Australian Capital Territory and the Northern Territory are each granted at least two members.

The AEC determines the number of members to which each State and Territory is entitled. The determination is made one year after the first sitting day for a new House of Representatives. A redistribution is postponed if it would begin within one year of the expiration of the House of Representatives, to prevent a general election from occurring while a redistribution is in progress.

On 13 November 2014 the AEC made a determination that resulted in Western Australia's entitlement increasing from 15 to 16 seats, and New South Wales's decreasing from 48 to 47 seats. A redistribution of electoral boundaries in New South Wales and Western Australia was undertaken before the 2016 election. The redistribution in New South Wales was announced on 16 October 2015, with the abolition of the Labor-held Division of Hunter. A redistribution also occurred in the Australian Capital Territory, as seven years had elapsed since the last time the ACT's boundaries were reviewed. The number of seats by States in the House of Representatives arising from the 2014 determination were as follows:

The first sitting of the current House of Representatives took place on 31 August 2016, and will expire on 29 August 2019. On 31 August 2017, the AEC announced a further determination after completion of processing of the 2016 census. The determination will result in a redistribution in South Australia (which had lost 1 seat), Victoria (which had gained 1 seat) and the ACT (which had also gained 1 seat). This will increase the number of seats from 150 to 151. A draft redistribution in Victoria was released on 6 April 2018, and the final distribution was released on 12 July.

A redistribution of State divisions is required in three circumstances:A redistribution is undertaken on a State-by-State basis. After the redistribution process commences, a Redistribution Committee — consisting of the Electoral Commissioner, the Australian Electoral Officer for the State concerned (in the ACT, the senior Divisional Returning officer), the State Surveyor General and the State Auditor General — is formed. The Electoral Commissioner invites public suggestions on the redistribution which must be lodged within 30 days. A further period of 14 days is allowed for comments on the suggestions lodged. The Redistribution Committee then divides the State or Territory into divisions and publishes its proposed redistribution. A period of 28 days is allowed after publication of the proposed redistribution for written objections. A further period of 14 days is provided for comments on the objections lodged. These objections are considered by an augmented Electoral Commission — consisting of the four members of the Redistribution Committee and the two part-time members of the Electoral Commission.

At the time of the redistribution the number of electors in the divisions may vary up to 10% from the 'quota' or average divisional figure but at a point 3.5 years after the expected completion of the redistribution, the figures should not vary from the average projected quota by more or less than 3.5%. Thus the most rapidly growing divisions are generally started with enrolments below the quota while those that are losing population are started above the quota.

Neither the Government nor the Parliament can reject or amend the final determination of the augmented Electoral Commission.

Boundaries for the Australian House of Representatives and for the six state and two territorial legislatures are drawn up by independent authorities, at the federal level by the Australian Electoral Commission (AEC) and in the states and territories by their equivalent bodies. Politicians have no influence over the process, although they, along with any other citizen or organisation, can make submissions to the independent authorities suggesting changes.

There is significantly less political interference in the redistribution process than is common in the United States. In 1978, federal Cabinet minister Reg Withers was forced to resign for suggesting to another minister that the name of a federal electorate be changed to suit a political ally.

There have been examples of malapportionment of federal and state electoral districts in the past, often resulting in rural constituencies containing far fewer voters than urban ones and maintaining in power those parties that have rural support despite polling fewer popular votes. Past malapportionments in Queensland, Western Australia and the 'Playmander' in South Australia were notorious examples of the differences between urban and rural constituency sizes than their population would merit. The Playmander distorted electoral boundaries and policies that kept the Liberal and Country League in power for 32 years from 1936 to 1968. In extreme cases, rural areas had four times the voting value of metropolitan areas. Supporters of such arrangements claimed Australia's urban population dominates the countryside and that these practices gave fair representation to country people.

The redistribution, creation and abolition of divisions is the responsibility of the AEC. When new divisions are created, the AEC will select a name. Most divisions are named in honour of prominent historical people, such as former politicians (often Prime Ministers), explorers, artists and engineers, and rarely for geographic places.

Some of the criteria the AEC uses when naming new divisions are:

From 1901 to 1949, the House consisted of either 74 or 75 members (the Senate had 36). Between 1949 and 1984, it had between 121 and 127 members (the Senate had 60 until 1975, when it increased to 64). In 1977, the High Court ordered that the size of the House be reduced from 127 to 124 members to comply with the nexus provision. In 1984, both the Senate and the House were enlarged; since then the House has had between 148 and 150 members (the Senate has 76).

Parliament of Australia

The Parliament of Australia (also known as the Commonwealth Parliament or just Parliament) is the legislative branch of the government of Australia. It consists of three elements: the Crown (represented by the Governor-General), the Senate and the House of Representatives. The combination of two elected chambers, in which the members of the Senate represent the states and territories while the members of the House represent electoral divisions according to population, is modelled on the United States Congress. Through both chambers, however, there is a fused executive, drawn from the Westminster System.

The upper house, the Senate, consists of 76 members: twelve for each state, and two each for the Northern Territory (including Christmas Island and the Cocos (Keeling) Islands) and the Australian Capital Territory (including Norfolk Island and the Jervis Bay Territory). Senators are elected using the single transferable vote proportional representation system and as a result, the chamber features a multitude of parties vying for power. The governing party or coalition has not held a majority in the Senate since 1981 (except between 2005–2008) and usually needs to negotiate with other parties and Independents to get legislation passed.

The lower house, the House of Representatives, currently consists of 150 members, each elected using full-preference instant-runoff voting from single-member constituencies known as electoral divisions (and commonly referred to as "electorates" or "seats"). This tends to lead to the chamber being dominated by two major political groups, the centre-right Coalition (consisting of the Liberal and National Parties) and the centre-left Labor Party. The government of the day must achieve the confidence of this House in order to gain and remain in power.

Although elections can be called early, every three years the full House of Representatives and half of the Senate is dissolved and goes up for reelection. A deadlock-breaking mechanism known as a double dissolution can be used to dissolve the full Senate as well as the House in the event that the Upper House twice refuses to pass a piece of legislation passed by the Lower House.

The two Houses meet in separate chambers of Parliament House (except in a rare joint sitting) on Capital Hill in Canberra, Australian Capital Territory.

The Commonwealth of Australia came into being on 1 January 1901 with the federation of the six Australian colonies. The inaugural election took place on 29 and 30 March and the first Australian Parliament was opened on 9 May 1901 in Melbourne by Prince George, Duke of Cornwall and York, later King George V. The only building in Melbourne that was large enough to accommodate the 14,000 guests was the western annexe of the Royal Exhibition Building. After the official opening, from 1901 to 1927 the Parliament met in Parliament House, Melbourne, which it borrowed from the Parliament of Victoria (which sat, instead, in the Royal Exhibition Building until 1927).
It had always been intended that the national Parliament would sit in a new national capital. This was a compromise at Federation due to the rivalry between the two largest Australian cities, Sydney and Melbourne, which both wished to become the new capital. The site of Canberra was selected for the location of the nation's capital city in 1908. A competition was announced on 30 June 1914 to design Parliament House, with prize money of £7,000. However, due to the start of World War I the next month, the competition was cancelled. It was re-announced in August 1916, but again postponed indefinitely on 24 November 1916. In the meantime, John Smith Murdoch, the Commonwealth's Chief Architect, worked on the design as part of his official duties. He had little personal enthusiasm for the project, as he felt it was a waste of money and expenditure on it could not be justified at the time. Nevertheless, he designed the building by default.

The construction of Old Parliament House, as it is called today, commenced on 28 August 1923 and was completed in early 1927. It was built by the Commonwealth Department of Works, using tradesmen and materials from all over Australia. The final cost was about £600,000, which was more than three times the original estimate. It was designed to house the parliament for a maximum of 50 years until a permanent facility could be built, but was actually so used for more than 60 years.

The building was opened on 9 May 1927 by the Duke and Duchess of York (later King George VI and Queen Elizabeth The Queen Mother). The opening ceremonies were both splendid and incongruous, given the sparsely built nature of Canberra of the time and its small population. The building was extensively decorated with British Empire and Australian flags and bunting. Temporary stands were erected bordering the lawns in front of the Parliament and these were filled with crowds. A Wiradjuri elder, Jimmy Clements, was one of only two aboriginal Australians present, having walked for about a week from Brungle Station (near Tumut) to be at the event. Dame Nellie Melba sang the National Anthem (at that time "God Save the King"). The Duke of York unlocked the front doors with a golden key, and led the official party into King's Hall where he unveiled the statue of his father, King George V. The Duke then opened the first parliamentary session in the new Senate Chamber.

In 1978 the Fraser government decided to proceed with a new building on Capital Hill, and the Parliament House Construction Authority was created. A two-stage competition was announced, for which the Authority consulted the Royal Australian Institute of Architects and, together with the National Capital Development Commission, made available to competitors a brief and competition documents. The design competition drew 329 entries from 29 countries.

The competition winner was the Philadelphia-based architectural firm of Mitchell/Giurgola, with the on-site work directed by the Italian-born architect Romaldo Giurgola, with a design which involved burying most of the building under Capital Hill, and capping the edifice with an enormous spire topped by a large Australian flag. The façades, however, included deliberate imitation of some of the patterns of the Old Parliament House, so that there is a slight resemblance despite the massive difference of scale. The building was also designed to "sit above" Old Parliament House when seen from a distance.

Construction began in 1981, and the House was intended to be ready by Australia Day, 1988, the 200th anniversary of European settlement in Australia. It was expected to cost. Neither the deadline nor the budget was met. In the end it cost more than A$1.1 billion to build.

The New Parliament House was finally opened by Queen Elizabeth II, Queen of Australia on 1988, the anniversary of the opening of both the first Federal Parliament in Melbourne on 1901, and of the Provisional Parliament House in Canberra on 1927.

The Constitution establishes the Commonwealth Parliament, consisting of three components: the Queen of Australia, the Senate and the House of Representatives.

Most of the constitutional functions of the Crown are given to the Governor-General, whom the Queen appoints on the advice of the Prime Minister to act as her representative in Australia. Specifically, the Constitution gives the Governor-General the power to assent to legislation, refuse to assent, or to reserve a bill for the Queen's pleasure. However, by convention, the Governor-General does not exercise these powers, other than in accordance with the advice of the Prime Minister.

The upper house of the Australian Parliament is the Senate, which consists of 76 members. Like the United States Senate, on which it was partly modelled, the Australian Senate includes an equal number of Senators from each state, regardless of population. Unlike it, however, the Australian Senate has always been directly elected. (The US Senate has been directly elected only from 1913.)

The Constitution allows Parliament to determine the number of Senators by legislation, provided that the six original states are equally represented. Furthermore, the Constitution provides that each original state is entitled to at least six Senators. However, neither of these provisions applies to any newly admitted states, or to territories. Pursuant to an Act of Parliament passed in 1973, Senators are elected to represent the territories. Currently, the two Northern Territory Senators represent the residents of the Northern Territory as well as the Australian external territories of Christmas Island and the Cocos (Keeling) Islands. The two Australian Capital Territory Senators represent the Australian Capital Territory, the Jervis Bay Territory and since 1 July 2016, Norfolk Island. While only half of the State Senate seats go up for re-election each three years (except in the case of a double dissolution) as they serve six year terms, all of the Territory Senators must face the voters every three years.

Until 1949, each state elected the constitutional minimum of six Senators. This number increased to ten from the 1949 election, and was increased again to twelve from the 1984 election. The system for electing Senators has changed several times since Federation. The original arrangement used a first-past-the-post block voting or "winner takes all" system, on a state-by-state basis. This was replaced in 1919 by preferential block voting. Block voting tended to produce landslide majorities and even "wipe-outs". For instance, from 1920 to 1923 the Nationalist Party of Australia had 35 of the 36 Senators, and from 1947 to 1950, the Australian Labor Party had 33 of the 36 Senators.

In 1948, single transferable vote proportional representation on a state-by-state basis became the method for electing Senators. This change has led to the rise of a number of minor parties such as the Democratic Labor Party, Australian Democrats and Australian Greens who have taken advantage of this system to achieve parliamentary representation and the balance of power. From the 1984 election, group ticket voting was introduced in order to reduce a high rate of informal voting but in 2016, group tickets were abolished to avoid undue influence of preference deals amongst parties that were seen as distorting election results and a form of optional preferential voting was introduced.

Section 15 of the Constitution provides that a casual vacancy of a State Senator shall be filled by the State Parliament. If the previous Senator was a member of a particular political party the replacement must come from the same party, but the State Parliament may choose not to fill the vacancy, in which case Section 11 requires the Senate to proceed regardless. If the State Parliament happens to be in recess when the vacancy occurs, the Constitution provides that the State Governor can appoint someone to fill the place until fourteen days after the State Parliament resumes sitting. The State Parliament can also be recalled to ratify a replacement.

The lower house of the Australian Parliament, the House of Representatives, is made up of single member electorates with roughly the same population. As is convention in the Westminster System, the party or coalition of parties that has the majority in this House forms the Government with the leader of that party or coalition becoming the Prime Minister. If the government loses the confidence of the House, they are expected to call a new election or resign.

Parliament may determine the number of members of the House of Representatives but the Constitution provides that this number must be "as nearly as practicable, twice the number of Senators"; this requirement is commonly called the "nexus provision". Hence, the House presently consists of 150 members. Each state is allocated seats based on its population; however, each original state, regardless of size, is guaranteed at least five seats. The Constitution does not guarantee representation for the territories. Parliament granted a seat to the Northern Territory in 1922, and to the Australian Capital Territory in 1948; these territorial representatives, however, had only limited voting rights until 1968. Federal electorates have their boundaries redrawn or redistributed whenever a state or territory has its number of seats adjusted, if electorates are not generally matched by population size or if seven years have passed since the most recent redistribution.

From the beginning of Federation until 1918, first-past-the-post voting was used in order to elect members of the House of Representatives but since the 1918 Swan by-election which Labor unexpectedly won with the largest primary vote due to vote splitting amongst the conservative parties, the Nationalist Party of Australia government, a predecessor of the modern-day Liberal Party of Australia, changed the lower house voting system to Instant-runoff voting, which in Australia is known as full preferential voting, as of the subsequent 1919 election. This system has remained in place ever since, allowing the Coalition parties to safely contest the same seats. Full-preference preferential voting re-elected the Bob Hawke government at the 1990 election, the first time in federal history that Labor had obtained a net benefit from preferential voting.

It is not possible to be simultaneously a member of both the Senate and the House of Representatives, but a number of people have been members of both Houses at different times in their parliamentary career (see List of people who have served in both Houses of the Australian Parliament).

Only Australian citizens are eligible for election to either house. They must not also hold citizenship of a "foreign power". When the Constitution was drafted, all Australians were British subjects, so the word "foreign" meant non-British. But, in the landmark case "Sue v Hill" (1999), the High Court of Australia ruled that, at least since the Australia Act 1986, Britain has been a "foreign power", so that British citizens are also excluded.

Compulsory voting was introduced for federal elections in 1924. The immediate justification for compulsory voting was the low voter turnout (59.38%) at the 1922 federal election, down from 71.59% at the 1919 federal election. Compulsory voting was not on the platform of either the Stanley Bruce-led Nationalist/Country party coalition government or the Matthew Charlton-led Labor opposition. The actual initiative for change was made by Herbert Payne, a backbench Tasmanian Nationalist Senator who on 16 July 1924 introduced a private Senator's bill in the Senate. Payne's bill was passed with little debate (the House of Representatives agreeing to it in less than an hour), and in neither house was a division required, hence no votes were recorded against the bill. The 1925 federal election was the first to be conducted under compulsory voting, which saw the turnout figure rise to 91.4%. The turnout increased to about 95% within a couple of elections and has stayed at about that level since.

Since 1973, citizens have had the right to vote upon turning 18. Prior to this it was 21.

Australian Federal Police officers armed with assault rifles have been situated in both chambers of the Federal Parliament since 2015. It is the first time in Australian history that a parliament has possessed armed personnel.

Each of the two Houses elects a presiding officer. The presiding officer of the Senate is called the President; that of the House of Representatives is the Speaker. Elections for these positions are by secret ballot. Both offices are conventionally filled by members of the governing party, but the presiding officers are expected to oversee debate and enforce the rules in an impartial manner.

The Constitution authorises Parliament to set the quorum for each chamber. The quorum of the Senate is one-quarter of the total membership (nineteen); that of the House of Representatives is one-fifth of the total membership (thirty). In theory, if a quorum is not present, then a House may not continue to meet. In practice, members usually agree not to notice that a quorum is not present, so that debates on routine bills can continue without other members having to be present. Sometimes the Opposition will "call a quorum" as a tactic to annoy the Government or delay proceedings, particularly when the Opposition feels it has been unfairly treated in the House. The session of the relevant House is suspended until a quorum is present. It is the responsibility of the Government whips to ensure that, when a quorum is called, enough Government members are present to make up a quorum.

Both Houses may determine motions by voice vote: the presiding officer puts the question, and, after listening to shouts of "Aye" and "No" from the members, announces the result. The announcement of the presiding officer settles the question, unless at least two members demand a "division", or a recorded vote. In that case the bells are rung throughout Parliament House summoning Senators or Members to the chamber. During a division, members who favour the motion move to the right side of the chamber, whereas those opposed move to the left. They are then counted by the "tellers" (Government and Opposition whips), and the motion is passed or defeated accordingly. In the Senate, in order not to deprive a state of a vote in what is supposed to be a states' house, the President is permitted a vote along with other Senators (however, that right is rarely exercised); in the case of a tie, the President does not have a casting vote and the motion fails. In the House of Representatives, the Speaker does not vote, except in the case of a tie (see casting vote).

Most legislation is introduced into the House of Representatives and goes through a number of stages to become a law. The first stage is a first reading, where the legislation is introduced to the chamber, then there is a second reading, where a vote is taken on the general outlines of the bill. The legislation can then be considered by a House committee, which reports back to the House on any recommendations. This is followed by a consideration in detail stage, where the House can explore the bill in detail and make any amendments. This is finally followed by a third reading, where the bill is either passed or rejected by the House. If passed, the legislation is then sent to the Senate, which has a similar structure of debate and passage except that the consideration in detail stage is replaced by a committee of the whole. Once a bill has been passed by both Houses in the same form, it is then presented to the Governor-General for Royal Assent.

The principal function of the Parliament is to pass laws, or legislation. Any Senator or Member may introduce a proposed law (a bill), except for a money bill (a bill proposing an expenditure or levying a tax), which must be introduced in the House of Representatives. In practice, the great majority of bills are introduced by ministers. Bills introduced by other Members are called private members' bills. All bills must be passed by both Houses to become law. The Senate has the same legislative powers as the House, except that it may not amend money bills, only pass or reject them. The enacting formula for Acts of Parliament is simply "The Parliament of Australia enacts:".

The Commonwealth legislative power is limited to that granted in the Constitution. Powers not specified are considered "residual powers", and remain the domain of the states. Section 51 grants the Commonwealth power over areas such as taxation, external affairs, defence and marriage. Section 51 also allows State parliaments to refer matters to the Commonwealth to legislate.

Section 96 of the Australian Constitution gives the Commonwealth Parliament the power to grant money to any State, "on such terms and conditions as the Parliament thinks fit". In effect, the Commonwealth can make grants subject to States implementing particular policies in their fields of legislative responsibility. Such grants, known as "tied grants" (since they are tied to a particular purpose), have been used to give the federal parliament influence over state policy matters such as public hospitals and schools.

The Parliament performs other functions besides legislation. It can discuss urgency motions or matters of public importance: these provide a forum for debates on public policy matters. Senators and Members can move motions of censure against the government or against individual ministers. On most sitting days in both Houses there is a session called Question Time at which Senators and Members address questions to the Prime Minister and other ministers. Senators and Members can also present petitions from their constituents. Both Houses have an extensive system of committees in which draft bills are debated, evidence is taken and public servants are questioned. There are also joint committees, composed of members from both Houses.

In the event of conflict between the two Houses over the final form of legislation, the Constitution provides for a simultaneous dissolution of both Houses – known as a double dissolution. Section 57 of the Constitution states that, ""If the House of Representatives passes any proposed law, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, and if after an interval of three months the House of Representatives, in the same or the next session, again passes the proposed law with or without any amendments which have been made, suggested, or agreed to by the Senate, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, the Governor-General may dissolve the Senate and the House of Representatives simultaneously.""

In an election following a double dissolution, each state elects their entire 12-seat Senate delegation, while the two territories represented in the Senate each elect their two senators as they would in a regular federal election. Because all seats are contested in the same election, it is easier for smaller parties to win seats under the single transferable vote system: the quota for the election of each senator in each Australian state in a full Senate election is 7.69% of the vote, while in a normal half-Senate election the quota is 14.28%.

If the conflict continues after such an election, the Governor-General may convene a joint sitting of both Houses to consider the bill or bills, including any amendments which have been previously proposed in either House, or any new amendments. If a bill is passed by an absolute majority of the total membership of the joint sitting, it is treated as though it had been passed separately by both Houses, and is presented for royal assent. With proportional representation, and the small majorities in the Senate compared to the generally larger majorities in the House of Representatives, and the requirement that the number of members of the House be "nearly as practicable" twice that of the Senate, a joint sitting after a double dissolution is more likely than not to lead to a victory for the House over the Senate. This provision has only been invoked on one occasion, after the election following the 1974 double dissolution. However, there are other occasions when the two Houses meet as one: see Joint meetings of the Australian Parliament.

In addition to the work of the main chambers, both the Senate and the House of Representatives also have a large number of committees which deal with matters referred to them by their respective Houses. They provide the opportunity for all Members and Senators to ask questions of ministers and public officials as well as conduct inquiries, examine policy and legislation. Once a particular inquiry is completed the members of the committee can then produce a report, to be tabled in Parliament, outlining what they have discovered as well as any recommendations that they have produced for the Government to consider.

The ability of the Houses of Parliament to establish committees is referenced in Section 49 of the Constitution, which states that, ""The powers, privileges, and immunities of the Senate and of the House of Representatives, and of the members and the committees of each House, shall be such as are declared by the Parliament, and until declared shall be those of the Commons House of Parliament of the United Kingdom, and of its members and committees, at the establishment of the Commonwealth.""

Parliamentary committees can be given a wide range of powers. One of the most significant powers is the ability to summon people to attend hearings in order to give evidence and submit documents. Anyone who attempts to hinder the work of a Parliamentary committee may be found to be in contempt of Parliament. There are a number of ways that witnesses can be found in contempt, these include; refusing to appear before a committee when summoned, refusing to answer a question during a hearing or to produce a document, or later being found to have lied to or misled a committee. Anyone who attempts to influence a witness may also be found in contempt. Other powers include, the ability to meet throughout Australia, to establish subcommittees and to take evidence in both public and private hearings.

Proceedings of committees are considered to have the same legal standing as proceedings of Parliament, they are recorded by Hansard, except for private hearings, and also operate under Parliamentary privilege. Every participant, including committee members and witnesses giving evidence, are protected from being prosecuted under any civil or criminal action for anything they may say during a hearing. Written evidence and documents received by a committee are also protected.

Types of committees include:

Standing Committees, which are established on a permanent basis and are responsible for scrutinising bills and topics referred to them by the chamber; examining the government's budget and activities (in what is called the budget estimates process); and for examining departmental annual reports and activities.

Select Committees, which are temporary committees, established in order to deal with particular issues.

Domestic Committees, which are responsible for administering aspects of the Parliament's own affairs. These include the Selection Committees of both Houses that determine how the Parliament will deal with particular pieces of legislation and private members business and the Privileges Committees that deal with matters of Parliamentary Privilege.

Legislative Scrutiny Committees, which examine legislation and regulations to determine their impact on individual rights and accountability.

Joint Committees are also established to include both members of the House of Representatives and the Senate.

Under the Constitution, the Governor-General has the power to appoint and dismiss "Ministers of State" who administer government departments. In practice, the Governor-General chooses ministers in accordance with the traditions of the Westminster System that the Government be drawn from the party or coalition of parties that has a majority in the House of Representatives, with the leader of the largest party becoming Prime Minister.

These ministers then meet in a council known as Cabinet. Cabinet meetings are strictly private and occur once a week where vital issues are discussed and policy formulated. The Constitution does not recognise the Cabinet as a legal entity; it exists solely by convention. Its decisions do not in and of themselves have legal force. However, it serves as the practical expression of the Federal Executive Council, which is Australia's highest formal governmental body. In practice, the Federal Executive Council meets solely to endorse and give legal force to decisions already made by the Cabinet. All members of the Cabinet are members of the Executive Council. While the Governor-General is nominal presiding officer, she or he almost never attends Executive Council meetings. The Governor-General is bound by convention to follow the advice of the Executive Council on almost all occasions, giving it de facto executive power. A senior member of the Cabinet holds the office of Vice-President of the Executive Council and acts as presiding officer of the Executive Council in the absence of the Governor-General. The Federal Executive Council is the Australian equivalent of the Executive Councils and privy councils in other Commonwealth realms such as the Queen's Privy Council for Canada and the Privy Council of the United Kingdom.

A minister is not required to be a Senator or Member of the House of Representatives at the time of their appointment, but their office is forfeited if they do not become a member of either house within three months of their appointment. This provision was included in the Constitution (section 64) to enable the inaugural Ministry, led by Edmund Barton, to be appointed on 1 January 1901, even though the first federal elections were not scheduled to be held until 29 and 30 March.

After the 1949 election, John Spicer and Bill Spooner became ministers in the Menzies Government on 19 December, despite their terms in the Senate not beginning until 22 February 1950.

The provision was also used after the disappearance and presumed death of the Liberal Prime Minister Harold Holt in December 1967. The Liberal Party elected John Gorton, then a Senator, as its new leader, and he was sworn in as Prime Minister on 10 January 1968 (following an interim ministry led by John McEwen). On 1 February, Gorton resigned from the Senate to stand for the 24 February by-election in Holt's former House of Representatives electorate of Higgins due to the convention that the Prime Minister be a member of the lower house. For 22 days (2 to 23 February inclusive) he was Prime Minister while a member of neither house of parliament.

On a number of occasions when Ministers have retired from their seats prior to an election, or stood but lost their own seats in the election, they have retained their Ministerial offices until the next government is sworn in.

The Constitution of Australia established the Senate as part of the new system of dominion government in newly federated Australia. From a comparative governmental perspective, the Australian Senate exhibits distinctive characteristics. Unlike upper Houses in other Westminster system governments, the Senate is not a vestigial body with limited legislative power. Rather it was intended to play – and does play – an active role in legislation. Rather than being modelled solely after the House of Lords, as the Canadian Senate was, the Australian Senate was in part modelled after the United States Senate, by giving equal representation to each state. The Constitution intended to give less populous states added voice in a Federal legislature, while also providing for the revising role of an upper house in the Westminster system.

One of the functions of the Senate, both directly and through its committees, is to scrutinise government activity. The vigour of this scrutiny has been fuelled for many years by the fact that the party in government has seldom had a majority in the Senate. Whereas in the House of Representatives the government's majority has sometimes limited that chamber's capacity to implement executive scrutiny, the opposition and minor parties have been able to use their Senate numbers as a basis for conducting inquiries into government operations.

The constitutional text denies the Senate the power to originate or amend appropriation bills, in deference to the conventions of the classical Westminster system. Under a traditional Westminster system, the executive government is responsible for its use of public funds to the lower house, which has the power to bring down a government by blocking its access to supply – i.e. revenue appropriated through taxation. The arrangement as expressed in the Australian Constitution, however, still leaves the Senate with the power to reject supply bills or defer their passage – undoubtedly one of the Senate's most powerful abilities.

The ability to block supply was the origin of the 1975 Australian constitutional crisis. The Opposition used its numbers in the Senate to defer supply bills, refusing to deal with them until an election was called for both Houses of Parliament, an election which it hoped to win. The Prime Minister of the day, Gough Whitlam, contested the legitimacy of the blocking and refused to resign. The crisis brought to a head two Westminster conventions that, under the Australian constitutional system, were in conflict – firstly, that a government may continue to govern for as long as it has the support of the lower house, and secondly, that a government that no longer has access to supply must either resign or be dismissed. The crisis was resolved in November 1975 when Governor-General Sir John Kerr dismissed Whitlam's government and appointed a caretaker government on condition that elections for both Houses of parliament be held. This action in itself was a source of controversy and debate continues on the proper usage of the Senate's ability to block supply and on whether such a power should even exist.

The blocking of supply alone cannot force a double dissolution. There must be legislation repeatedly blocked by the Senate which the government can then choose to use as a trigger for a double dissolution.

Members of the Australian Parliament do not have legal immunity: they can be arrested and tried for any offence. They do, however, have Parliamentary privilege: they cannot be sued for anything they say in Parliament about each other or about persons outside the Parliament. This privilege extends to reporting in the media of anything a Senator or Member says in Parliament. The proceedings of parliamentary committees, wherever they meet, are also covered by privilege, and this extends to witnesses before such committees.

From the beginning of Federation until 1987, Parliamentary privilege operated under Section 49 of the Constitution, which established the privileges of both Houses and their members to be the same as the House of Commons of the United Kingdom at the time of the Constitution's enactment. The Parliament was also given the power to amend its privileges. In 1987, the Parliament passed the "Parliamentary Privileges Act", which clarified the meaning and extent of privilege as well as how the Parliament deals with breaches.

There is a legal offence called contempt of Parliament. A person who speaks or acts in a manner contemptuous of the Parliament or its members can be tried and, if convicted, imprisoned. The Parliament previously had the power to hear such cases itself, and did so in the Browne–Fitzpatrick privilege case, 1955. This power has now been delegated to the courts. There have been few convictions. In May 2007, Harriet Swift, an anti-logging activist from New South Wales was convicted and reprimanded for contempt of Parliament, after she wrote fictitious press releases and letters purporting to be from Federal MP Gary Nairn as an April Fools' Day prank.

Radio broadcasts of Parliamentary proceedings began on 10 July 1946. They were originally broadcast on Radio National. Since August 1994 they have been broadcast on ABC NewsRadio, a government-owned channel set up specifically for this function. It operates 24 hours a day and broadcasts other news items when parliament is not sitting.

The first televised parliamentary event was the historic 1974 Joint Sitting. Regular free-to-air television broadcasts of Question Time began in August 1990 from the Senate and February 1991 from the House of Representatives. Question Time from the House of Representatives is televised live, and the Senate Question Time is recorded and broadcast later that day. Other free-to-air televised broadcasts include: the Treasurer's Budget speech and the Leader of the Opposition's reply to the Budget two days later; the opening of Parliament by the Governor-General; the swearing-in of Governors-General; and addresses to the Parliament by visiting heads of state.

In 2009, the Pay TV company Foxtel launched A-SPAN, now called A-PAC or "Australia's Public Affairs Channel", which broadcasts live sittings of the House of Representatives and the Senate, parliamentary Committee meetings and political press conferences.

The Parliament House official website provides free extensive daily proceedings of both chambers as well as committee hearings live on the Internet.

The current Parliament is the 45th Australian Parliament. The most recent federal election was held on 2 July 2016 and the 45th Parliament first sat on 30 August.

The outcome of the 2016 election saw the first-term incumbent Liberal/National Coalition re-elected with 76 seats in the 150-seat House of Representatives (a decrease of 14 seats), a bare one-seat majority government − the closest federal majority result since the 1961 election. The Shorten Labor opposition won 69 seats, an increase of 14 seats. On the crossbench, the Australian Greens, the Nick Xenophon Team, Katter's Australian Party, and independents Andrew Wilkie and Cathy McGowan won a seat each.

The Senate result saw the Liberal/National Coalition with 30 seats (−3), Labor with 26 (+1), the Greens with 9 (−1), One Nation with 4 (+4) and Nick Xenophon Team with 3 (+2). Derryn Hinch won a seat representing his Justice Party, while Liberal Democrat David Leyonhjelm, Family First's Bob Day, and Jacqui Lambie retained their seats. The number of crossbenchers increased by two to a record 20. The Liberal/National Coalition required at least nine additional votes to reach a Senate majority, an increase of three. The Liberal/National Coalition and Labor parties agreed that the first elected six of twelve Senators in each state would serve a six-year term, while the last six elected in each state would serve a three-year term, despite two previous bipartisan senate resolutions to use an alternative method to allocate long and short term seats. By doing this, Labor and the Coalition each gained one Senate seat from 2019.

Bob Day, of the Family First Party, resigned from the Senate on 1 November 2016 following the collapse of his business. His eligibility to have stood in the 2016 election was referred by the Senate to the High Court, sitting as the Court of Disputed Returns. In April 2017 the court found that Day was not validly elected at the 2016 election and ordered that a special recount of South Australian ballot papers be held in order to determine his replacement. The court announced that Lucy Gichuhi was elected in his place on 19 April 2017. On 26 April 2017, Family First merged with the Australian Conservatives; however, Gichuhi declined to join the new party, announcing she would sit as an independent.

Rodney Culleton, who had left Pauline Hanson's One Nation Party on 19 December 2016 to become an independent, had his eligibility to stand in the 2016 election challenged on two constitutional grounds. Among the grounds of ineligibility provided in Constitution section 44, a person cannot sit in either house of the Parliament if they are bankrupt or have been convicted of a criminal offence carrying a potential prison sentence of one year or more.

Culleton was declared bankrupt by the Federal Court on 23 December 2016. On 11 January 2017, after receiving an official copy of the judgment, the President of the Senate declared Culleton's seat vacant. Culleton's appeal against that judgment was dismissed by a full court of the Federal Court on 3 February 2017.

This judgment was followed later on the same day by the High Court's decision that Culleton was ineligible owing to conviction for a criminal offence carrying a potential prison sentence of one year or more. This was a decision as the Court of Disputed Returns following a reference by the Senate at the same time as with Day. It was decided that, since Culleton's liability to a two-year sentence for larceny had been in place at the time of the 2016 election, he had been ineligible for election and that this was not affected by the subsequent annulment of that conviction; the Court also held that the resulting vacancy should be filled by a recount of the ballot, in a manner to be determined by a single Justice of the Court. Following that recount, on 10 March 2017 the High Court named Peter Georgiou as his replacement, returning One Nation to 4 seats.

On 7 February 2017, South Australian Senator Cory Bernardi resigned from the Liberal Party, to form a new party called the Australian Conservatives.

Throughout the later half of 2017, several members of the Parliament, including Deputy Prime Minister of Australia Barnaby Joyce, have had their eligibility for parliament challenged for breach of section 44 of the Constitution, due to dual citizenships. The High Court unanimously ruled on 27 October 2017 that a dual citizen is disqualified from taking seat in parliament, unless he/she had taken "all steps reasonably required by foreign law to renounce his or her citizenship of a foreign power". This meant that five parliamentarians were ineligible to take their seat. After the judgement, many other members of parliament have also been found to have dual citizenship and disqualified.

The Senate has included representatives from a range of political parties, including several parties that have seldom or never had representation in the House of Representatives, but which have consistently secured a small but significant level of electoral support, as the table shows.

Results represent the composition of the Senate after the elections. The full Senate has been contested on eight occasions; the inaugural election and seven double dissolutions. These are underlined and highlighted in puce.

A two-party system has existed in the Australian House of Representatives since the two non-Labor parties merged in 1909. The 1910 election was the first to elect a majority government, with the Australian Labor Party concurrently winning the first Senate majority. Prior to 1909 a three-party system existed in the chamber. A two-party-preferred vote (2PP) has been calculated since the 1919 change from first-past-the-post to preferential voting and subsequent introduction of the Coalition. ALP = Australian Labor Party, L+NP = grouping of Liberal/National/LNP/CLP Coalition parties (and predecessors), Oth = other parties and independents.

This is a list of members of the Australian Senate following the 2016 double dissolution election on 2 July 2016. All 76 senators were elected due to the election being the result of a double dissolution, and not an ordinary half-senate election. The terms of half of the senators representing each of the six states of Australia were allocated six-year terms ending on 30 June 2022 with the remainder allocated three-year terms ending on 30 June 2019. The terms of senators from the states can only be truncated if another double dissolution election is called. The terms of senators from the Australian Capital Territory and the Northern Territory end on the next dissolution of the House of Representatives.

Members of the Australian Senate, 2016–2019

In accordance with section 13 of the Constitution, it was left to the Senate to decide which Senators were allocated the full six-year terms ending on 30 June 2022 and which Senators were allocated three-year terms ending on 30 June 2019. The senate resolved that the first elected six of twelve Senators in each state would serve six-year terms, while the last six elected in each state would serve three-year terms. This was the Senate practice on the seven previous occasions that have required allocation of long and short terms. In 1983 the Joint Select Committee on Electoral Reform had unanimously recommended an alternative "recount" method to reflect proportional representation, and section 282 of the "Commonwealth Electoral Act" was inserted to provide for a recount on that basis. This alternative method had been supported by both Labor and the Coalition in bipartisan senate resolutions passed in 1998 and 2010.