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Home > Markets and Payments > SONIA reform

SONIA reform

In July 2015 the Bank announced its plans to reform the SONIA benchmark.  These reforms will become effective on 23 April 2018. 

Overall, the reform process will result in:

  • the Bank being the administrator, including the calculation and publication of SONIA;
  • the coverage of SONIA being broadened to include overnight unsecured transactions negotiated bilaterally as well as those arranged via brokers, using the Bank’s Sterling Money Market Data Collection, Form SMMD as data source;
  • the averaging methodology for calculating SONIA changing to a volume-weighted trimmed mean; and
  • the publication of SONIA moving to 09:00 on the business day following that to which the rate pertains.

The Bank has undertaken several rounds of consultation on the reforms of SONIA (see key resources).  The SONIA Key Features and Policies document provides users of SONIA with a consolidated summary of how SONIA will be calculated and administered, including the governance arrangements, following the implementation of the reforms.

SONIA Key Features and Policies

If you have queries relating to SONIA reform, please email