Federation credit
The Federation credit was a monetary unit used by the United Federation of Planets. 

Although it was stated on more than one occasion that the economy of the future was very different, and that money no longer existed on Earth from as early as the late 22nd century or in the Federation as late as the 24th century, this medium of exchange did still exist within that period. All known examples of credit use were via transactions outside or on the periphery of the Federation. (; ; )

In 2267, Engineer DeSalle euphemistically wagered "credits to navy beans" that the  could penetrate a force field with its impulse drive. ()

Later that same year, Uhura was offered a tribble for ten credits by a bartender on Deep Space Station K-7, a border outpost on the edge of Federation space. She later received one gratis from fellow Federation citizen Cyrano Jones. ()

In the 2250s, the Federation placed a bounty of 100,000 credits on Harry Mudd. ()

In 2269, Harry Mudd was selling love potion crystals on Motherlode, a planet outside Federation jurisdiction, for three hundred credits apiece. () 

Almost a century later, the Federation would have paid the Barzanian Planetary Republic, a non-Federation government, 1.5 million Federation credits as a lump sum and then 100,000 credits every Barzanian year for the rights to the Barzan wormhole. The transaction never transpired, once the wormhole's instability became apparent. (, okudagram)

See also
 Credit chip
 Terran Imperial credit, an equivalent monetary unit in the Mirror universe.

External link 
 

de:Credit
Currency
Federation