system
Given the following post, respond as if you're commenting on Reddit:
human
In Star Trek If the Federation did not have/need currency how did they barter with other species?
gpt
The UFP as a whole does not have currency/credit per se - but many people have different mass/energy allocations due to either their socio-economic status or responsibilities.

While this is not money - every living being is allocated, at a minimum, enough mass/energy (power and raw materials for replicators/transporter uses, etc) to live a comfortable and satisfactory life, if you contribute to society as a whole, you receive additional allocations commensurate with your contribution to society.  As well, those who choose to engage in private enterprises can receive compensation equivalent to a portion of someone else's current mass/energy accumulation.

A certain portion of this mass/energy, in common parlance, is called a credit, or Federation credit.  Any person and/or government who is not a member of the federation of planets can redeem these credits in goods and/or services at any time.  Member planets and/or local governments can choose to handle their individual economies under the concept of local autonomy, with the caveat that participation in that local economy is voluntary, and anyone can 'vote with their feet' if they choose not to participate.

Mass/Energy is used due to the way that the post-scarcity society of Replicator technology works.  Replicators can create virtually any known substance, except for whose with strange properties like dilithium crystals and latinum, but it is cheaper, in terms of energy cost, to take existing particles and assemble them in the replicator, versus creating those particular particles from pure energy. (Mass/Energy equations/E=mc^2 stuff)