In the Star Trek universe, the economic system is a utopian post-scarcity system referred to as the “New World Economy.” Markets are, mostly, obsolete, but they do still exist where they are needed. Most importantly, the Federation have replicators which can instantly convert energy into almost any matter, form or material they desire. Therefore, there are few, if any, material wants in Star Trek. You don’t need to trade because almost anything you desire can be produced for free at the touch of a button. And if you don’t need to trade then you don’t need money.
We see from the following episodes and movies that money is not used:
– Star Trek IV: Captain Kirk says to McCoy “They’re still using money, we need to get some.” Kirk later tells Gillian that they don’t use money in the 23rd Century.
– The Next Generation (TNG) episode ‘The Neutral Zone’: Captain Picard says to Offenhouse that they have “eliminated hunger, want, the need for possessions.”
– First Contact: Picard describes how money does not exist in the 24th Century. “We work to better ourselves and the rest of humanity.”
– Deep Space 9 (DS9) episode ‘In the Cards’: Nog suggests that Jake bids on a baseball card and Jake replies: “I’m human, I don’t have any money.” Nog responds: “It’s not my fault that your species decided to abandon currency-based economics in favor of some philosophy of self-enhancement.” Jake quips back: “Hey, watch it. There’s nothing wrong with our philosophy. We work to better ourselves and the rest of humanity.”
– Voyager (VOY) episode ‘Random Thoughts’: Janeway is clearly unaccustomed to using money in the marketplace.
– VOY ‘Dark Frontier’: Paris says “Well, uh, when the New World Economy took shape in the late 22nd century and money went the way of the dinosaur, Fort Knox was turned into a museum.”
However, conflicting information from other episodes and movies suggests that money is used in the Star Trek universe:
– The Original Series (TOS) episode ‘Mudd’s Women’: Captain Kirk mentions paying the miners on Rigel XII for dilithium crystals.
– TOS episode ‘Errand of Mercy’: Kirk tells Spock that the Federation has invested a great deal of money in the training of Starfleet staff.
– TOS episode ‘The Trouble with Tribbles’: Cyrano Jones negotiates the price of Tribbles with a bartender.
– Star Trek III: Dr. McCoy negotiates with an alien about his transfer to Genesis, and asserts that he would have enough money for that.
– Star Trek VI: Scotty mentions that he is going to buy a boat.
– TNG episode ‘The Price’: The Federation bids 1,500,000 federation credits for a wormhole.
– TNG episode ‘A Matter of Perspective’: Dr. Apgar’s motivation for building the Krieger wave generator was to sell it to the highest bidder.
– DS9 episode ‘Little Green Men’: Quark sells a damaged shuttle to a scrapyard in the Sol system.
– VOY episode ‘The Gift’: Tuvok and Janeway buy a meditation lamp from a Vulcan master who doubles the price on seeing the Starfleet insignia.
What we can conclude from all this is that money does exist in the Star Trek universe, but it is only used to acquire goods that are impossible to replicate and to interact with societies that lack replication technology.
As for Federation currency, they use latinum, a rare silver coloured liquid that, due to its density and complexity, cannot be replicated. Latinum is frequently used as currency in Star Trek and does not appear to have any value except as a token of unreplicatable trading.