SONIA

The Sterling Overnight Index Average, abbreviated as SONIA, is the principal risk-free interest rate benchmark for sterling markets, administered by the Bank of England and published each London business day at 09:00 UK time for the previous day’s transactions. Introduced in March 1997 and transferred to Bank of England administration in April 2016 , SONIA was reformed with a transactions-based methodology effective 23 April 2018. It is calculated as the trimmed mean of eligible unsecured overnight sterling deposit rates, based on the central 50% of the volume-weighted distribution, and is accompanied by the SONIA Compounded Index to support compounded-in-arrears conventions.