In TNG, Picard says that the Federation has evolved past a need for money. Indeed, we never see any.
In DS9 though, Quark talks a lot about bar tabs and costs. Surely O’Brien and Bashir don’t get free drinks, so how do they pay? I’d assume that any Ferengi worth his lobes won’t accept anything that can be replicated, so do Federation officers get a stipend of tradeable “value” when interacting with cultures that still expect payment?
I think there’s also a reference to Quark paying rent to Sisko for running the bar. Presumably that’s denominated in latinum. I wonder where it goes? Maybe the secret “Garak black ops” fund.
My working theory is that Federation Economists make a distinction between a monetary system and a credit system. Credits can buy food, clothing, shelter, and nice things to enjoy. Money does all that, as well, but also can be invested with the hope of making more money than you started with. There is no Federation stock market.