• The Sterling Overnight Index Average, or SONIA, is an index of very short-term unsecured loans between UK financial institutions.

  • Launched in 1997, several changes made in 2017 and 2018 resulted in the SONIA rate becoming the preferred risk-free reference rate for UK securities dealers.
  • This is due to the fact that the LIBOR rate and its calculation methodology have been criticized for fixing and fraud.