Each of the 29 billion coins currently in use in the United Kingdom, as well as the currencies of Commonwealth nations including Australia, New Zealand, and Canada, bear the portrait of Queen Elizabeth II.
King Charles III is now the monarch, thus coins with his likeness will enter circulation. However, Dominic Chorney from coin experts A.H. Baldwin & Sons says that money with the queen’s likeness won’t be phased out any time soon.
I don’t think there will be a deliberate attempt to take her coins out, Chorney told CNBC.
He predicted that Queen Elizabeth coins would continue to circulate for many years to come. “The coins will be lost over time,” he stated.

Normally, pound coins can be used for about 30 years before they start to lose their usefulness.
Prior to decimalization, which took place in early 1971 and reduced the value of the pound sterling from pounds, shillings, and pence to just pounds and pence, it was usual to find portraits of former kings on currency.
Coins honouring George VI, George V, and Queen Elizabeth II would have been in circulation. Perhaps even some very, very old coins with Queen Victoria on them,” Chorney suggested.
There’s also no practical reason to try to get rid of the coins with the late queen’s face, he said, since they are still considered legal money.

Because no one can recall seeing two separate kings in circulation, having coins of King Charles III and Queen Elizabeth II in circulation will be a first in contemporary history, according to Chorney.
King Charles III will face which direction.
It has been customary for many centuries to depict the monarch on coins. According to Chorney, it ensures a currency and represents power.

The emperor, the ruler, or the king is the most evident symbol of the state since Roman times, according to Chorney, who added that a currency can be believed if it is backed by the state.

The faces of monarchs on coins have always faced opposite directions with each new coronation since 1659, at the end of the Protectorate, when the head of state of the United Kingdom was the Lord Protector Oliver Cromwell rather than a king or queen.
Charles II chose to have his portrait towards his left when he ascended to the throne in 1661, the opposite direction from Cromwell, who had Charles I executed.
According to rumours, the action symbolised the new king or queen turning his or her back on Cromwell’s republican interpretation of Britain, and the custom persisted each time a new monarch came to the throne.

The lone exception to the rule almost came from Edward VIII. Because he abdicated less than a year after ascending to the throne, his coins were never produced. His coins were intended to face the same way as his father’s to depict his more attractive side. The custom was reinstated when his brother and successor, George VI, chose to stand in the opposite direction from his father.
Since her accession to the throne in 1952, Queen Elizabeth II has appeared in five distinct portraits on British coins. The most current, which Jody Clark created, was the first to be made entirely from photographs as opposed to a sitting with the queen.

The official coin manufacturer for the United Kingdom, the Royal Mint, declined to comment on the new coins that will feature a portrait of King Charles III, but it did send the following statement via email: “The Royal Mint worked with Her Late Majesty throughout her reign – detailing her journey from new Queen to respected head of state across five coin portraits, and ensuring each new UK coin received her personal seal of approval. For many years to come, the astonishing legacy of Britain’s longest-reigning king will endure.

The Bank of England, which prints the money for the United Kingdom, announced that banknotes bearing the portrait of the queen would continue to be accepted as legal tender and promised to make further pronouncements “after the period of mourning has been respected.”