Postage stamp prepaying. From when the first postage stamps were used, postmarks were applied to prevent the stamps being used again. The first stamp, the "Penny black", became available for purchase 1 May 1840, to be valid as of 6 May 1840. Two days later, 8 May 1840, the Two penny blue was introduced. The Penny black was sufficient for a letter less than half an ounce to be sent anywhere within the UK. Both stamps included an engraving of the young Queen Victoria, without perforations, as the first stamps were separated from their sheets by cutting them with scissors. The first
Postage stamp demonetization November 2000 are valid for postage. Irish stamps denominated in pounds were demonetized on 31 December 2002. Stamps issued since 2 August 2000 are valid for postage. In Malta, all stamps denominated in Maltese pounds were demonetized in 2008. All stamps issued since 29 December 2006 are valid for postage. Mail franked with older stamps is marked STAMP NOT VALID and postage due is charged. Stamps of the Netherlands denominated in guilders were demonetized on 1 November 2013. It is not possible to exchange guilder stamps for ones denominated in euros. Portuguese stamps denominated in escudos were demonetized in 2002.