Treasury bills are government securities, with an original maturity of less than one year. Treasury bills do not pay any fixed or floating interest during the life of the bill. A Treasury bill is therefore a zero-coupon security. This means that the bill is issued at a discount, i.e. the offer price is lower than the face value and the return on the bill will be the difference between the offer price and the face value paid at maturity.
Treasury bills are normally issued in connection with IMM dates each year. The IMM dates are the third Wednesday in March, June, September and December. New 12-month Treasury bills are issued on each IMM date. Existing Treasury bills are usually expanded at auctions held between the IMM dates.