Department of the Treasury
From Halopedia, the Halo wiki
The Department of the Treasury is formerly a cabinet department and treasury department of the United States of America. Under the Unified Earth Government, it is the umbrella government organization for the IRS.
Officers of the Treasury enforce laws against counterfeiting and other economic laws in the UEG, at least in the territories that were once the United States, now reformed into the United Republic of North America.