A special Commons sitting began at midday on Friday and was scheduled to go through to 10pm, allowing MPs to remember the late monarch.
Opening the special sitting, Ms Truss said Her Majesty was “one of the greatest leaders the world has ever known”.
She added: “We remember the pledge she gave on her 21st birthday to dedicate her life to service.
“The whole house will agree - never has a promise been so completely fulfilled.”
Adding: “She reinvented monarchy for the modern age, and she was a champion of freedom and democracy.”
Leader of the Opposition Sir Keir Starmer said the Queen “had a relationship with us all” and that the country “loved her”.
Sir Keir praised the Queen for her support during the lockdown which “gave people strength and courage when they needed it most”.
He added: “Covid closed the doors of all parts of the country. It made our loves smaller...but she held the nation close, in a way no one else could have done.”
Turning to King Charles, Sir Keir said the nation wishes him a “long, happy, and successful” reign.
He also said nations across the world and their tributes are a reminder of the esteem held for Her Majesty.
Sir Keir concluded: “As we move forward, to a better path and a better future, she will always be with us. May she rest in peace. God save the King.”
The Westminster leader of the SNP, Ian Blackford, was next to pay tribute to the monarch. He spoke about Balmoral and its special relationship with the Queen.
In his own tribute, Boris Johnson said the Queen was a “figurehead for our entire system”.
He added: “Think of what we asked of her, and think of what she gave. She showed the world how to give, how to love and how to serve.”
Revealing his last meeting with the Queen earlier this week, Mr Johnson said the Queen “was as radiant and as knowledgeable and as fascinated by politics as ever.”
Former Prime Minister Theresa May began her own speech with her tribute to the Queen as a mother.
“Queen Elizabeth II was quite simply the most remarkable person I have ever met,” Mrs May said.
She went on to say that the Queen was a woman of “compassion” who had a “deep understanding of her people”.
In conclusion, Mrs May said: “She was remarkable and I doubt we will ever see her like again.”
Iain Duncan Smith told a series of comical anecdotes involving the Queen while DUP leader Sir Jeffrey Donaldson praised the Queen for her trip to Ireland and subsequent calls to end the violence in Northern Ireland.
The House will sit on Saturday from 2pm, when MPs will start taking the oath to the King.
All other parliamentary business will be postponed until after September 21.
The Government is pressing ahead with key policies such as delivering the energy plan by October to limit gas and electricity bills this winter. Ms Truss became the 15th Prime Minister during the Queen’s reign at a “kissing hands” ceremony at Balmoral Castle on Tuesday.
The Queen succeeded to the throne in 1952, when Winston Churchill was Prime Minister. Anthony Eden was the first Prime Minister appointed by Her Majesty, in 1955.
Harold Macmillan, who succeeded Eden in 1957, wrote in his diary that at his first audience he told the Queen “half in joke, half in earnest, that I could not answer for the new government lasting more than six weeks”, adding: “She smilingly reminded me of this at an audience six years later.”
After Macmillan retired due to ill health, the Queen appointed Alec Douglas-Home as Prime Minister in 1963. In 1964, Harold Wilson became the Queen’s first Labour Prime Minister, being re-elected in 1966 but he was beaten by Edward Heath in 1970.
In early 1974, Heath went to the strikes-hit country on “who governs Britain” and the result was not him as the General Election produced a hung Parliament.
Back came Wilson into Downing Street and he called another general election in October 1974, winning a wafer-thin majority of only three seats.
After his unexpected resignation in 1976, he was succeeded by James Callaghan who was PM for the Queen’s Silver Jubilee in 1977.
Following the “winter of discontent”, Margaret Thatcher was the first female Prime Minister to be appointed by the Queen in 1979, serving three consecutive terms.
When she was ousted by her own party in 1990, John Major surprised many by winning the 1992 election with his “soap box” campaigning. The Queen’s long reign is reflected in the fact that Tony Blair was born in the year of her official Coronation in 1953. Gordon Brown became Prime Minister in 2007, though he never won a General Election.
The Queen appointed David Cameron in 2010 to form the first coalition Government in nearly 70 years.
He won the 2015 election but quit after the shock 2016 Brexit referendum.
Her Majesty was reported to have built up a close bond with Theresa May who was toppled over her Brexit plans in 2019. Boris Johnson was Prime Minister for her Platinum Jubilee this year, before his tumultuous three-year premiership ended on Tuesday.