The Queen will turn 95 on Wednesday, four days after Philip's funeral service in St George's Chapel at Windsor Castle.
In what would have been a week with numerous celebratory occasions, events will be toned down to reflect a period of grief for the family .
The Queen is staying at Windsor with around 20 staff members, dubbed HMS Bubble.
An official previously said the royals will observe two weeks of what is known as royal mourning, which began on April 9 when Philip died aged 99, during which public engagements will continue appropriate to the circumstances.
Last year, the Queen decided not to celebrate her birthday in a special way during the first coronavirus lockdown, opting to speak with family members through private video calls.
She spent her 94th birthday with Prince Philip but stayed away from other members of the family as they followed social distancing rules amid the pandemic.
The bells of Westminster Abbey - the church where she was married and crowned - stayed silent on her birthday for the first time in more than a decade last year.
There were also no birthday gun salutes after the Queen decided the celebratory display of military firepower would not be "appropriate" at the time.
Her official birthday is celebrated in June and is usually marked by the annual Trooping the Colour parade, although that will not go ahead in its traditional form for a second year due to the pandemic.
In a statement, Buckingham Palace said options for a parade in the quadrangle at Windsor Castle are being considered.
Also celebrating his birthday this week is the Duke and Duchess of Cambridge's youngest son Prince Louis, who turns three on Friday.
Prince William and the Duchess of Cambridge, Kate Middleton, will also be celebrating a decade of marriage the following week on April 29.
It is not known how long the Duke of Sussex will stay in the UK, although there is speculation he might fly back to the US on Monday to rejoin his wife although he may decide to stay on for his grandmother's birthday.
Harry arrived on the Sunday before the funeral and had been self-isolating at the couple's former home, Frogmore Cottage, in Windsor.
It was the first time the duke had met up with his family since Harry and Meghan's interview with Oprah Winfrey, which was broadcast last month.
The royal family came together to say their final farewell to Philip at a funeral service on Saturday, with households seated two metres apart to follow Covid-19 regulations.
It meant the Queen had to sit alone in the chapel, clad in mourning black and wearing a face covering like the rest of the limited congregation of 30.
As the world watched, she bowed her head during the national minute's silence in honour of her late husband.
The one-hour service, between 3pm and 4pm, was viewed by 11 million people on the BBC.