A bill is a type of short-term U.S. government debt instrument that typically has a maturity of one year or less. These bills are sold at a discount from their par value, meaning that the price paid is lower than the face value received at maturity. The interest earned on these bills is calculated as the difference between the face value and the discounted price. This makes bills an attractive investment option for those seeking a low-risk, short-term return on their money.