Treasury bills are the bills, the government issues with maturity period of one year or less than one year. Treasury bills are usually issued as discount securities. Discount treasuries are issued at a discount to par value and mature at par value. These are similar to zero-coupon bonds and they carry no coupon rate. The difference between the purchase price and the maturity value is the interest earned or the return to the investor. Treasury bills are issued with initial maturity of 91 days, 182 days and 364 days. They are more popularly referred to as 3-month, 6-month and 1-year treasury bills.