He is the longest-waiting heir to the throne in Britain's history, having moved into that role since 1952, when he was 3 years old.
Palace officials said today the future king will contribute the government pension to a charity that helps elderly people.
He is entitled to about USD 175 per week because of his service in the Royal Navy and because of voluntary contributions he has made.
The prince will mark his milestone birthday representing his mother, Queen Elizabeth II, at the Commonwealth heads of government meeting in Sri Lanka.