A trust fund is a fiduciary activity dealing with the stewardship of property. Unlike the federal trusts covered elsewhere in this website, real trust funds deal with investments, real cash, real estate, precious metals and/or jewels or any viable or negotiable assets entrusted to trustees by whoever established the trust.

At the close of fiscal 2005, the federal government listed 160 trust funds, 143 of which have absolutely nothing to do with the statement above, are not real trust funds, and hold nothing but nonmarketable Treasury bonds, markers that are demands on the U.S. Treasury that will be covered by future taxes or money borrowed. However, the 17 others are real trust funds:
(AS OF CLOSE OF FISCAL 2005)
Because they don't know where else to put these, or simply to hide them somewhat, the Treasury lists these real trust funds as part of "Debt Held by the Public" or what should properly be called Investor Debt. Then they classify these trusts as "not subject to the debt limit."

The "Thrift Savings fund," that you can read about elsewhere on this site, is composed partly of Treasury investments (member choice) which would place them under "Public Debt" anyway. These are then subtracted from the determination of "debt not subject to the limit."

When at or holding slightly below the debt ceiling, and income tax receipts are not enough, the Secretary of the Treasury will often turn to these trust funds for operating cash or to keep the government going. This is when you hear politicians complaining that "he's using our money."

The last point brings up or reinforces the question of whether we can really trust politicians or the federal government to manage a real trust fund holding our supplemental retirement money, Social Security surpluses. Although the word "privatize" is politically unpopular today, at least trustees in the private sector would be accountable or not above the law.