Treasury bills (T-bills) are short-term (one year or less) debt securities issued by a government. The duration of a T-bill could either be 91, 182, or 364 days. T-bills are sold at a discount with the same face value. When the T-bill matures, the government pays you the full face value. Your profit will come from the difference between what you paid for the T-bill and the amount you receive upon maturity.