Most races have a medium of exchange with which they buy and sell goods with other world as well as among their own people.
The value of a given currency on the interstellar market is usually dependent on the wealth, or perceived wealth of the race that controls it. [1] Not all races poses currency and instead rely on pure barter or a credit system for trade. The Hyach for example consider currency to be vulgar.[2]
Earth Alliance Credits
The Earth Alliance uses a credit based system, mostly for book keeping purposes and is exchanged via a computer credit chit that stores the owner's account details and DNA to prevent forgery.[3] Visitors to Earth Alliance territory must usually exchange their native money at a local exchange, assuming it is a recognised currency and are then issued a credit chit that is tied to their EA account. Those who live and work in the Alliance have their salaries paid directing into their credit accounts.[4] After Mars was declared a free and independent planet within the Alliance, the former colony gained the right to produce their own currency, in addition to passports and Identicards, at least in theory. In practice certain parties in Earthdome delayed putting the new Martian data into the system in order to force Mars citizens into using Earth documentation because it wasn't worth the trouble. To counter this, ISA President Sheridan offers the Interstellar Alliance's help by suggesting they set up a diplomatic office on Minbar and help the Mars Provisional Government establish an account outside Earth's jurisdiction.[5]
Centauri Ducats
The Centauri Republic economy runs on a hard currency called "Ducats". [6]