A Horizon label is an adhesive postage label that is a type of variable value stamp.
The labels were introduced in the United Kingdom in 2002[1] as part of the computerisation of the counter services of the post office network of Royal Mail using the Horizon System.
[2] The labels received a frosty reception from philatelists initially as they were seen as replacing postage stamps, but as they have become more complex and more stamp-like, collectors have warmed to them and they have now become a popular collecting specialism in the U.K. and an established part of modern British postal history.
[1] The first labels were large plain labels composed purely of text but later labels are of a gold colour with a Machin head and a repeating pattern of the words ROYALMAIL in order to prevent forgery.
The principal events in the development of the labels were:[3] The training of postal workers includes the use of voided horizon labels,[4] noted as early as 2003.