Credit

The credit, abbreviated as "cR," is the standard currency of the Unified Earth Government. As of 2553, the Credit is still in use. Credits can be spent in the form of "credit chips," which seem to be similar to a credit card. Humans sometimes casually refer to credits as "credaroos," analogous to the way 20th and 21st century Americans would refer to dollars as "buckaroos."

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

Trivia

 * Credits are the in-game currency used to purchase new armor permutations and armor effects in Halo: Reach. They also determine rank.
 * In the trailer of Halo 3: ODST, there are monitors that are intended to announce information to citizens. One of the messages says "Your tax dollars at work." As the dollar is no longer a functioning currency, the sign should really read tax credits, but it is likely that the iconic phrase has not changed since the 21st century.
 * According to Halo: The Fall of Reach, there are no coins or papers used in the credit system, but in the Audio Logs in Halo 3: ODST, an old woman is heard breaking an ATM with money in the form of coins and presumably paper coming out. Another ATM, found in gameplay, which also houses an Audio Log, is also constantly spitting out money until the Audio Log is collected. It is unknown whether this is an oversight or if the currency is different than credits.
 * If a Marine is killed with friendly fire in Halo 3, another one may say "Okay, now you owe me twenty credits!"
 * The headhunters Jonah and Roland would constantly bet twenty credits while on missions.
 * The Warthog trailer for Forza Motorsport 4 lists the price of the 2554 M12 Force Application Vehicle as 343,000 cR, which serves as a reference to 343 Industries rather than a canon price.

External

 * Bungie.net's review of the Civilian Warthog