The portrait of the king will appear on all four banknotes issued by the Bank of England — 5, 10, 20 and 50 pounds — with no other alterations to the existing designs. The notes will coexist alongside those featuring his late mother, Queen Elizabeth II, whom he succeeded as monarch on her death in September 2022.
The rollout of coins and stamps bearing the image of Charles have already been rolled out.
People may not notice the new notes immediately in their change or withdrawals from ATMs, not least because so many transactions are now done cashless.
Though cash payments have declined over the years, they remain particularly important for lower income households and those who get welfare benefits at their local Post Office. In 2023, legislation was passed as part of to protect access to cash.
In line with guidance from the Royal Household, the new notes will only be printed to replace those that are worn, and to meet any overall increase in demand — the approach aims to minimise the environmental and financial impact of the change.
There are more than 4.6 billion Bank of England notes in circulation, worth about 82 billion pounds ($105 billion).
"This is a historic moment, as it's the first time we've changed the sovereign on our notes," said Bank of England Governor Andrew Bailey. "We know that cash is important for many people, and we are committed to providing banknotes for as long as the public demand them. Bringing these new notes into circulation is a demonstration of that commitment."
In April, Charles was presented with the first banknotes bearing his portrait and praised them as "very well designed" while expressing his surprise at being only the second monarch to feature on them.
Although the Bank of England started to produce banknotes in the 17th century, Charles's mother, Queen Elizabeth II, was the first British monarch to be given the honour in 1960 on a 1-pound note.
People will be able to snap up the new-look currency at selected Post Office branches across the U.K.
"Our local customers come into our branch every day to withdraw or deposit cash for their daily needs, so we were excited to be one of the first branches to have the new banknotes available," said Karen Stonham, branch manager at the Portsmouth Post Office in southern England.