Short-term U.S. Treasury security having a maturity of up to one year and issued in denominations of $10,000 to $1 million. T-bills are sold at a discount: Investors purchase a bill at a price lower than the face value (for example, the investor might buy a $10,000 bill for $9,700) the return is the difference between the price paid and the amount received when the bill is sold or it matures (if held to maturity, the return on the T-bill in the example would be $300). T-bills are the type of security most frequently used in Federal Reserve open market operations.