What are Treasury bills?
Treasury bills (or T-bills) are short-term securities that mature in one year or less from their issue date. You buy T-bills for a price less than their par (face) value, and when they mature, Treasury pays you their par value. Your interest is the difference between the purchase price of the security and what we pay you at maturity (or what you get if you sell the bill before it matures). For example, if you bought a $10,000, 26-week Treasury bill for $9,750 and held it until maturity, your interest would be $250.
