Credit

The credit, abbreviated as "cR", is the standard currency of the UNSC. It is the only currency used by the UNSC that has yet been mentioned, and it is unclear if it is based off of any older money systems. As of 2552 cR is still in use.

There is no known Covenant monetary unit that can be compared to cR and the UNSC has no idea how much money their weapons would cost to replace.

In the trailer of Halo 3: ODST (Which takes place in the year 2552, during Halo 2) there are monitors that are intended to announce information to citizens. One of the messages says: "Your tax dollars at work." but it is likely a cliche left over from the 21st century.

Trivia

 * UNSC citizens sometimes casually refer to credits as credaroos, analogous to the way Americans refer to dollars as bucks.