Short-term (usually less than one year, typically three months) maturity promissory note issued by a national (federal) government as a primary instrument for regulating money supply and raising funds via open market operations. Issued through the country's 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 par-value (also called redemption value). This yield is closely watched by financial markets and affects the yield on municipal and corporate bonds and bank interest rates.