When the Queen dies and Charles III becomes King, what will happen to the current forms of money?
Charles apparently wants to call himself George VII when he becomes King, since the two previous Kings called Charles weren’t particularly successful. As far as currency is concerned, there shouldn’t be much difference. It’ll simply be that newly minted coins will have the new King’s head on them, but the older currency with the Queen’s head will still be perfectly legal tender. There will be no change in value apart from the usual rate of inflation. I remember before the decimal coinage came in in the early 1970s, there were still coins in common usage with every monarch’s head on them since Queen Victoria.