Queen Elizabeth the world’s longest-reigning current monarch won’t be able to officially retire without abdicating her throne, according to royal succession rules. But she would be able to stop all of her royal duties if her health were to become a concern.

Queen Elizabeth II is set to retire from her royal duties in 18 months, to make way for Prince Charles to assume the throne.
According to Metro News, HRH Elizabeth will still be the Queen, in title, but with Prince Charles taking over the day-to-day running of the royal family.
The 93-year-old monarch is reportedly weighing stepping down around her 95th birthday, the same age that her husband, Prince Philip, withdrew from his royal duties.