Treasury bill

A short-term government debt instrument that pays no coupon and is sold at a discount to its face value, the return being the gap between the price paid and the amount repaid. India's central government issues them for 91, 182 and 364 days through weekly RBI auctions; the US Treasury issues them for up to a year.

A 91-day bill bought at ₹98.50 and repaid at ₹100 earns ₹1.50, an annualised yield of 6.11%.

Treasury bills are the closest thing to a risk-free asset in each currency. So the 91-day yield is the usual cash return in a Sharpe ratio and the short end of the yield curve. Money market funds and banks park surplus cash in them, and so do companies, because they can be sold quickly at a predictable price.

The cash return every risky asset is measured against.