31 U.S.C. § 322 — Working capital fund

(a) The Department of the Treasury runs a working capital fund. Money in this fund pays for administrative services the Secretary — with the approval of the Director of the Office of Management and Budget — decides can be run more cheaply and effectively as shared, central services, instead of each office paying for its own.

(b) Money in the fund does not expire; it stays available until it is spent. Congress can also add more money to the fund through regular appropriations.

(c) The fund is made up of: money Congress appropriates to it directly; the value of supply inventories, equipment, and other assets — including items already on order — that the Secretary transfers into the fund to help provide services, minus any debts or unpaid bills tied to them; money from selling or trading property; and payments received when fund property is lost or damaged.

(d) The fund gets paid back — or paid in advance — by the Department offices or other sources that use its services. It charges rates high enough to cover its own operating costs, including the cost of employees' unused annual leave building up and the depreciation of its buildings and equipment. At the end of each fiscal year, any money the Secretary decides the fund doesn't need gets deposited into the Treasury as ordinary government income.