William effectively left the RAF on Tuesday when he carried out his last shift as a search and rescue helicopter pilot following a three-year tour of duty.
The second in line to the throne is in a "transitional" year, sources have said, and is mulling over options for his "public service". An announcement will be made about his decision within the next 12 months.
Kensington Palace would not give details about what form the public service could take but there has been speculation William could take on a full-time role in an area he is passionate about - like the Duke of York's stint as the UK's roving business ambassador.
Kensington Palace said the Duke would continue to carry out royal engagements, but he is not expected to increase the number of official events he attends.
He will work towards expanding his core charitable interests particularly in the field of conservation of endangered species.
Kensington Palace said: "He will continue to support the work of the Queen and the Royal Family through a programme of official engagements, both at home and overseas, with the Duchess of Cambridge.
"The Duke will work closely over the next 12 months with the Royal Foundation of The Duke and Duchess of Cambridge and Prince Harry.
"The Duke will continue to work with his charities on issues relating to children and young people, veterans and serving members of the armed forces.
"The Duke and Duchess of Cambridge and Prince George are expected to move into their official residence at Kensington Palace within the next few weeks."
The Duke, known as Flight Lieutenant Wales in the air force, was based at RAF Valley on Anglesey.
The Cambridges will use their Kensington Palace apartment as their main home but are expected to move into their country retreat, Anmer Hall, in Norfolk, this year.