Short-term security one year and less, typically three months maturity promissory note issued by the ministry of Finance. This primary instrument is used for regulating money supply and raising funds via open market operations. Issued through the central bank, T-bills commonly pay no explicit interest but are sold at a discount, their yield being the difference between the purchase price and the Face-value (also called redemption value). T-bills are very popular with institutional investors because, being backed by the government's full faith and credit, they come closest to a risk free investment.