The Bank of England has announced the implementation date for the reformed Sterling Overnight Index Average Interest Rate Benchmark, known as SONIA. The BoE took over as administrator of SONIA on April 25, 2016. SONIA is currently based on a market for brokered deposits which has limited transaction volumes. From April 23, 2018, the methodology will change to a volume-weighted trimmed mean. The BoE will also take on the remaining aspects of administration, including the calculation and publication of SONIA. The reformed benchmark will cover overnight unsecured transactions negotiated bilaterally as well as those arranged via brokers, using the Bank's Sterling Money Market Data Collection as the data source. The BoE also published the Key features and policies for SONIA which is a summary of how SONIA will be calculated and administered, including the governance arrangements. The BoE intends to assess the benchmark's compliance with the Principles for Financial Benchmarks in due course.

View the SONIA Key Features and Policies document.

View the BoE's announcement.