Demise of the Crown is the legal term in the United Kingdom and the other Commonwealth realms for the transfer of the Crown upon the death or abdication of the monarch. The Crown transfers automatically to the monarch's heir. The concept evolved in the kingdom of England, and was continued in Great Britain and then the United Kingdom. The concept also became part of the constitutions of the British colonies, and was continued in the constitutions of the Commonwealth realms, until modified within those realms.
Originally, the demise of the Crown in England had significant legal effects: individuals who had been appointed to office by the deceased monarch lost their positions; if Parliament was sitting, it automatically dissolved; and actions in the royal courts automatically discontinued and had to be re-started. Almost all of these legal effects have been abolished by statutes of the British Parliament and the parliaments of the Commonwealth realms, so that the demise of the Crown no longer has much legal significance.
Although the concept of the demise of the Crown originally was based on the monarch's death, it was used in 1936 to describe the transfer of the Crown to George VI upon the abdication of Edward VIII, as the Act of Parliament that gave legal effect to the abdication specified that, upon the instrument of abdication taking effect, Edward VIII would cease to be King and there would be a demise of the Crown.
Other monarchies use different terminologies for the end of a reign.
If the monarch who dies or abdicates is the Queen and her successor is the King, references to 'Queen's' automatically changes to 'King's' - for example, lawyers in the Dominions of the Crown who are Queen's Counsel (Q.C.) at the time of the demise become King's Counsel (K.C.) without any need to seek new letters patent. The reverse is also true, as was the case from 6 February 1952 upon the death of King George VI, when living King's Counsel became Queen's Counsel.