It will eventually replace the "EIIR" stamp of Queen Elizabeth who died earlier this month after 70 years on the throne.
The new monogram for the UK's King Charles III -- which will appear on government buildings and post boxes -- has been unveiled.
Chosen by the new monarch from a series of designs, the cypher has the initials C, for Charles, and R for Rex, Latin for 'king'.
A version used in Scotland will feature the Scottish Crown.
It will eventually replace the "EIIR" stamp of Queen Elizabeth who died earlier this month after 70 years on the throne.
"The decision to replace cyphers will be at the discretion of individual organisations, and the process will be gradual," Buckingham Palace said in a statement.
The Court Post Office at the palace will frank its first items of mail using the new cypher on Tuesday.