A floating rate index is the reference rate that determines the variable part of the interest on a floating-rate instrument. The coupon on a floating rate note or loan is defined as the index plus a fixed margin. Common indices are overnight risk-free rates, such as SOFR for US dollars, SONIA for sterling and the euro short-term rate, together with term rates such as EURIBOR. Many older instruments referred to LIBOR, which was phased out, with the last US dollar panel settings ending in June 2023.
In security reference data, the index is a set of fields, not just a name. A record states the index, its tenor or compounding method, the margin, any cap or floor, the observation and lookback rules, and the fallback rate to be used if the index stops being published. These fields drive each coupon reset and reference rate reset. The general concept is described under interest rate index.