The new stamps are already on sale on the website.
Britain's Royal Mail began selling the first postage stamps featuring the image of King Charles III on Tuesday, following his ascension to the throne in September.
The monarch's portrait, unveiled in February and approved by Charles himself, will now appear on all Royal Mail stamps alongside the stamp's value and barcode, ahead of his coronation next month.
The so-called "definitive stamp" -- intended for everyday use -- is adapted from the official effigy that appears on new UK coins.
Retailers will continue selling existing stamps featuring the late Queen Elizabeth II and will be supplied with the new version when stocks run out.
The new stamps are already on sale on the website.
The image of Charles is adapted from a portrait by British sculptor Martin Jennings created for new UK coins, which are already in circulation.
The new design shows Charles facing left, as all British monarchs have done on stamps since the "Penny Black" was issued as the world's first postage stamp in 1840 under Queen Victoria.
The release also comes a day after stamp prices were increased by the postal service so that it could remain "sustainable", according to a Royal Mail statement.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)