At what point does a queen or king become queen or king?

A British royal becomes king/queen regnant immediately upon the death of the previous monarch usually his or her mother or father but of course it could be his or her aunt, uncle, cousin and so on.

Basically, there are two types of queen. One being a queen who rules in her own right who as aforementioned above inherited her predecessor's post. She is called queen regnant. The other type of queen is queen by marriage or queen consort. Monarch not just that of the British automatically becomes monarch at the moment of his or her predecessor's death and thus, even if he or she's not yet coronated, he or she is already the monarch. Not all monarchies have coronations though. Some just take oaths of protecting the country's constitution, etc.

Check this link for further information my son.

http://en.wikipedia.org/wiki/Act_of_Settlement_170...

Upon the death of the previous monarch - who could be their dad, mum, brother, sister, aunt, uncle, or cousin. As soon as a monarch dies, their heir immediately becomes Queen/King, hence the saying "The King/Queen is dead, long live the King/Queen". But you may also be referring to a King's wife, who becomes Queen upon her coronation.

As the reigning Monarch dies the Heir to the throne becomes the reigning Monarch,this is in the U.K. MONARCHY.,I cannot speak for other countries monarchies .

pretty sure its coronation. but im irish so dont quote me!