Administration of SONIA

Find out more about how we run the SONIA benchmark and our process for complaints and whistleblowing

SONIA meets international best practice for financial benchmarks 

We are responsible for the SONIA benchmark, a widely used interest rate benchmark.

We have designed our administration of SONIA so it meets the standards of international best practice set out in the International Organisation of Securities Commissions (IOSCO) Principles for Financial Benchmarks. We have published our statement of compliance with these principles.

The principles we follow 

Our governance protects the benchmark's integrity

Our governance arrangements protect the integrity of the SONIA benchmark and address any perceived conflicts of interest.   

Our Deputy Governor for Markets and Banking is accountable for its day-to-day administration, including calculation and publication. To support the governance arrangements there is an oversight function to provide challenge to the administration of SONIA. This comprises of the SONIA Oversight Committee, supported by the SONIA Stakeholder Advisory Group. 

SONIA Oversight Committee

The SONIA Oversight Committee provides challenge on our administration including the quality of the methodology and data we use to calculate SONIA. 

We publish the committee’s terms of reference, and its conflicts of interest code of practice. Given the SONIA Oversight Committee reviews highly commercially sensitive information the minutes of their meetings are not published.

SONIA Stakeholder Advisory Group

The SONIA Oversight Committee is supported by an SONIA Stakeholder Advisory Group, made up of relevant SONIA stakeholders. This group keeps us informed about how SONIA is working and give us advice on how it’s run.

We publish the group’s terms of reference (including membership) and the minutes of its meetings. 

We have a robust methodology

The methodology we use ensures SONIA captures transactions data from a dynamic and competitive market. We believe this is the best way to measure the underlying interest.

We periodically review the methodology to make sure it is still effective. We have structured our definition of it in two parts so our methodology can evolve, if necessary, in a way that minimises disruption to users.

We use high quality data

We base SONIA entirely on transactions that are reported to us. So it represents the market it measures. 

We use validation and plausibility checking to make sure the data are right. Senior Managers at each bank are personally accountable for the data they submit. In case there are issues, our short-term contingency arrangements are robust and transparent.

Find out more about the methodology and data we use in SONIA - Key features and policies

We’re open and accountable

We administer the benchmark in a way that’s open and accountable. 

We make available our key policies and external audits of our compliance with best practice.

We have a system for complaints and whistleblowing.

SONIA enquiries, complaints and whistleblowing

If you have a general enquiry about SONIA, please email

To make a complaint about SONIA, please email


We have established a whistleblowing mechanism to facilitate early awareness of potential misconduct or irregularities relating to SONIA.

Whistleblowing is when an employee reports suspected wrongdoing at work. An employee can report things that are not right, are illegal or if anyone at work is neglecting their duties, including:

  • someone’s health and safety is in danger
  • damage to the environment
  • a criminal offence
  • a person not obeying the law
  • covering up wrongdoing.

Firms are encouraged to consider setting up appropriate internal procedures which will encourage workers with concerns in relation to the SONIA benchmark to blow the whistle.

If your employer does not have an internal whistleblowing procedure, or if you do not feel able to use it, then contact us on +44 (0) 203 461 8703 during office hours or email us at or write to us at: 

IAWB Team, 
Legal Directorate, 
Bank of England, 
Threadneedle Street, 
London EC2R 8AH. 

Legal protection of whistleblowers

Under UK whistleblowing legislation, workers who make ‘protected disclosures’ have certain protection against detrimental treatment by their employer. While some types of disclosure to us are automatically protected in this way, disclosures relating to SONIA are not currently automatically protected.

However, a disclosure by a worker to a person other than their employer (such as to the Bank of England) can be a protected disclosure if it is carried out using a procedure which the worker’s employer has authorised the individual to use. 

If you are intending to make a disclosure to us in relation to SONIA, you should consider reviewing your employer’s whistleblowing procedures or consulting your workplace’s whistleblowing champion (if there is one) to determine whether your employer has authorised disclosure to the Bank of England. 

Whistleblowing to the Financial Conduct Authority (FCA) in relation to misconduct is treated as a protected disclosure. If you would prefer to whistleblow to the FCA, you can call 020 7066 9200 during office hours or email or write to:

Intelligence Department (ref PIDA), 
Financial Conduct Authority,
12 Endeavour Square,
London, E20 1JN

Note that the above is not a comprehensive statement of the law on whistleblowing. If you are in doubt as to your legal position, consider obtaining independent legal advice. 

Further guidance on whistleblowing is available from the UK Government.

Reform of SONIA in 2018

We reformed SONIA on 23 April 2018 by:

  • taking over responsibility for its calculation and publication from the Wholesale Market Brokers Association
  • broadening the data used to calculate it to includes overnight unsecured transactions negotiated bilaterally, as well as those arranged through brokers. 
  • changing the averaging methodology used to calculate it to a volume-weighted trimmed mean
  • changing publication to 9am on the following London business day (instead of 6pm on the same day) to give us time to process the larger volume of transactions it captures. 

We consulted on these reforms in July 2015, October 2016 and February 2017 and published a summary of the consultation feedback and design of SONIA in March 2017. We made available the ‘statistical characteristics of SONIA under the reformed and previous methodology’.  

This page was last updated 28 April 2023