Sterling Overnight Index Average. SONIA has been identified as the successor RFR for sterling markets and is administered by the Bank of England. SONIA measures the rate at which interest is paid on sterling short-term wholesale funds in circumstances where credit, liquidity and other risks are minimal, is calculated by reference to the rates paid by banks on overnight unsecured deposits in sterling made by other financial institutions, is produced as a percentage rate per annum for an overnight tenor only, is published for every London business day on a backward-looking T+1 basis and is subject to correction and republication at any point up to midday on the day of publication.

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