Postage stamps and postal history of the United States a precondition for their issue by a nation was the establishment of standardized rates for delivery throughout the country. If postal fees were to remain (as they were in many lands) a patchwork of many different jurisdictional rates, the use of stamps would only produce limited gains in efficiency, for postal clerks would still have to spend time calculating the rates on many letters: only then would senders know how much postage to put on them. The introduction of postage stamps in the UK in May 1840 was received with great interest in the United States (and around the world).
Postage stamps and postal history of South Sudan (see illustration). South Sudan is also using postage stamps for other than postage usage. For instance, the application fees for a post office box, 5 SSP, is paid in the form of five 1 SSP stamps, pasted on the application form itself. The central Government of South Sudan, however, has not issued any national revenue stamps. Only Central Equatoria State is known to have issued its own state revenue stamps, which are used on certain documents issued by the state, like Age Assessment Certificates. Central Equatoria State has been using also after independence of South Sudan the old three revenue