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Home > Markets and Payments > The SONIA interest rate benchmark

The SONIA interest rate benchmark

​Introduced in March 1997, SONIA is the Sterling Overnight Index Average.  It reflects bank and building societies’ overnight funding rates in the sterling unsecured market.  The Bank is currently taking steps to reform the SONIA interest rate benchmark, with SONIA moving to the new basis on 23 April 2018.

The Bank of England became the SONIA Administrator on 25 April 2016.

Institutional Arrangements

SONIA is designated as a specified benchmark under the Financial Services and Markets Act 2000 (FSMA). The Bank has designed its governance arrangements for administering SONIA to be consistent with the intent of regulations and international best practice, as encapsulated by the IOSCO Principles for Financial Benchmarks.

The Wholesale Market Brokers’ Association WMBA is acting as the Bank’s calculation and publication agent for the SONIA benchmark; this relationship is governed by a legal agreement.  The FCA regulates WMBA as the calculation and publication agent for the SONIA benchmark.

To support the Bank in its administration of the benchmark, there is a SONIA Advisory Committee consisting of external members.  Terms of reference for the SONIA Advisory Committee and meeting minutes are below.

SONIA Advisory Committee Terms of Reference
Minutes - SONIA Advisory Committee - 18 May 2016
Minutes - SONIA Advisory Committee - 20 September 2016
Minutes - SONIA Advisory Committee - 12 December 2016
Minutes – SONIA Advisory Committee – 16 March 2017
Minutes - SONIA Advisory Committee - 12 June 2017

If you have queries relating to the SONIA benchmark, please email

SONIA complaints procedure

If anyone wishes to submit a complaint, including concerning whether SONIA is representative of the underlying interest it seeks to measure, applications of the SONIA methodology, and other Bank of England decisions in relation to the determination of SONIA, they should submit this in writing to:

SONIA whistleblowing procedure