The Governor-General is Australia's head of state A s well as being the Queen's representative under s 2 of the Constitution, the Governor-General has significant head of state powers under s 61 of the Constitution.
Since the Constitution does not in terms identify our head of State, he or she must be the person who exercises the functions of the head of State. 
This can only be the Governor- General. The Sovereign's only constitutional function is to appoint or remove the Governor- General.
The claim that the Governor- General is our head of state is not some bizarre theory dreamed up in recent years for the republic debate. Lord Dufferin, then Governor-General of Canada, described a Governor-General as a constitutional head of state in a speech in 1873.
Constitutional scholars such as Professor D.A. Low, Dr David Butler, Professor Brian Galligan, and Professor Stuart Macintyre have also referred to the Governor- General as head of state. Prime Minister Gough Whitlam considered Sir John Kerr to be Australia's head of state.
The media refer to the Governor-General as head of state.
In 1977 the opening sentence of an editorial in The Canberra Times was: "We shall have today a new Governor-General, Sir Zelman Cowen, as our Head of State." In 1995 The Australian published a speech by Mr Bill Hayden under the heading: "The Governor- General has made one of the most controversial speeches ever delivered by an Australian Head of State."
Its next day's editorial said "it is perfectly appropriate at this stage of our constitutional development that the Head of State address important issues of social policy."
In 2003 The Australian's Editor- at-Large, Paul Kelly, was able to ask: "have Australians decided not by formal referendum but by informal debate that the Governor- General is our head of state?"
Sir Zelman Cowen, a distinguished constitutional lawyer, described the Governor- General as head of state in 1977 when Governor-General designate, and again in 1995, 13 years after leaving office. So too did Governor- General Sir Peter Cosgrove in an interview given in 2015.
The Governor-General was described as the head of state by former prime minister Bob Hawke while conducting a television interview with Governor-General Bill Hayden on   July 27, 1993; by Governor-General Bill Hayden in his farewell address to the parliament on   February 15,1996, on the eve of his retirement; by former New South Wales Premier Bob Carr; by former Governor of Victoria, Richard McGarvie; and by former Governor-General Sir Zelman Cowen.
The decision of the High Court in The King v The Governor of the State of South Australia (1907) 4 CLR 1497 settled the question. Sir Edmund Barton delivering the court's judgment said: "The Governor, as the officiating Constitutional Head of the State, is accordingly named as the person to whom the notification [of the Senate vacancy] is to be given ...
So, in certifying to the Governor- General the names of the Senators elected, chosen, or appointed the Governor must be regarded as acting [in] the capacity of the Constitutional Head of the State, being in that capacity the proper channel of communication with the officiating Constitutional Head of the Commonwealth, the Governor- General."
This decision has not been by- passed in recent years and left in a legal back-water. It was treated as good law by the High Court in 1981, 1987, 1988, and 1998. The passage of time and developments in constitutional law and practice have reinforced the conclusions reached by the Court in 1907.
Moreover in 1976 the Parliament declared the Governor-General to be our head of State in the Crimes (Internationally Protected Persons) Act passed to give effect to the Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons. Article 1 of the Convention provides that the term "internationally protected person means (a) a Head of State." Section 3A(1) of the Act provides: "For the purposes of this Act, the definition of 'internationally protected person' in paragraph 1 of article 1 of the Convention has effect as if the reference in that definition to a Head of State included, in relation to Australia, the Governor-General".
Thus the Constitution, the High Court, The Parliament, and current constitutional practice speak with one voice, the Governor-General is our head of state, and the Queen is our Sovereign.
Sir David Smith was official secretary to five Governors-General from 1973 to 1990. In retirement he has held three honorary appointments at the Australian National University: visiting fellow in the political science Programme of the Research School of Social Sciences; visiting fellow in the Faculty of Law; and visiting scholar in the College of Law.