Charles was officially proclaimed King on Saturday night (AEST) at a ceremony at St James's Palace in London.
Prime Minister Anthony Albanese will recommend Governor-General David Hurley issue the Australian proclamation on Sunday morning.
Mr Hurley is then expected to read the proclamation at Parliament House in Canberra at midday on Sunday, followed by a 21-gun salute.
State governors will make their own proclamations at ceremonies around the country.
NSW has announced free public transport all day so people can attend the historic event outside parliament from 12.30pm.
The Sydney Opera House sails will continue to be illuminated in the Queen's honour, as are other landmarks.
On Saturday, Mr Albanese, Mr Hurley, and Opposition Leader Peter Dutton laid wreaths to honour the Queen at Parliament House in Canberra.
"She was a constant reassuring presence," Mr Albanese said.
The prime minister and Mr Hurley will travel to London on Thursday to attend the funeral at Westminster Abbey.
It will take place on Monday September 19 at 8pm AEST.
Before then, the Queen's coffin will be driven from Balmoral Castle to Scotland's capital Edinburgh and be flown to London later in the week.
It will remain at Buckingham Palace before being taken to Westminster Hall to lie in state for four days, allowing the public to pay their respects.
While no formal mourning period has been declared - unlike the United Kingdom, which has set aside 10 days - Australians continued to publicly mourn on Saturday.
Sandra Alexandridis, of Reservoir, burst into tears outside Melbourne's makeshift memorial while remembering the Queen.
"She was a rock of society ... it's like you've lost your grandmother," she told AAP.
Warren Fairfax, 82, visited Government House in Sydney on Saturday, 65 years after receiving a Queen's Scout award there signed by her.
"I wanted to come back and just pay respects to her … I just wanted to do that today," Mr Fairfax told AAP.
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