What is SOFR? An Intro To The Secured Overnight Financing Rate

Key Learnings:

• SOFR is a measure/benchmark of the cost of borrowing (interest rate based) cash overnight collateralised by the U.S. Treasury securities, replacing the
• The rate is calculated by the Federal Reserve Bank of New York as a volume weighted medium of transaction-level tri-party repo data collected from the Bank of New York Mellon and U.S. Department of the Treasury’s Office of Financial Research.
• SOFR is a near risk-free rate calculated based on the cost of borrowing overnight, secured by the U.S. Treasury securities; while LIBOR had credit and liquidity risks, where banks were lending money to one another, making it unsecure.

The financial markets underwent a groundbreaking shift when the Secured Overnight Financing Rate (SOFR) was introduced to replace the London Interbank Offered Rate (LIBOR). This transition affected trillions of dollars in financial contracts worldwide. Understanding SOFR is now essential for anyone working with interest rate derivatives, loans, or bonds in U.S. dollar markets.

In this article we will cover what SOFR is, how it works, the SOFR rates, practical considerations, and limitations you should keep in mind when working with SOFR-based instruments.

What is SOFR?

The Secured Overnight Financing Rate (abbreviated to SOFR), is a benchmark interest rate that reflects the cost of borrowing cash overnight while using U.S. Treasury securities as collateral . The Federal Reserve Bank of New York publishes this rate daily, drawing from actual transaction data in the Treasury repurchase agreement market.

Why was SOFR Created to Replace LIBOR?

The journey to SOFR began after the 2012 LIBOR scandal exposed fundamental weaknesses in how benchmark rates were determined. In 2017, the Federal Reserve established the Alternative Reference Rates Committee (ARRC) to identify a robust replacement for U.S. dollar LIBOR. After careful evaluation, SOFR was selected and officially launched in April 2018. The transition accelerated when regulators announced that most LIBOR settings would cease after June 30, 2023, forcing financial institutions worldwide to adapt their systems, contracts, and risk management frameworks. Major institutions including the FHLB System, FNMA, and The World Bank quickly began issuing debt using SOFR as the index, signaling broad market acceptance.

Some of the key reasons SOFR was chosen include:

• SOFR is based on an active underlying market with a diverse set of borrowers and lenders
• Near risk-free rate
• More secured and stable
• Transaction-based
• Compliance with international best practices
• Serves diverse market segments, supporting strong transaction volumes across varying market conditions.

What is the Difference Between LIBOR and SOFR?

The key difference is that SOFR is a secured rate backed by U.S. Treasury securities and carries almost no credit risk, whilst LIBOR was an unsecured rate based on interbank lending that included credit and liquidity risks.

LIBOR and SOFR serve similar purposes as benchmark rates, but their construction differs fundamentally. These differences matter because they affect how loans are priced, how derivatives are valued, and how financial institutions manage risk across their portfolios.

Here’s how they compare:

What are the Alternatives to SOFR Internationally?

While SOFR serves as the U.S. dollar benchmark, other major economies developed their own alternative reference rates following similar principles.

SOFR and the alternatives:

The UK adopted SONIA (Sterling Overnight Index Average), published by the Bank of England and available through gov.uk regulatory channels.

Each of these rates follows the same philosophy: basing benchmarks on observable transactions rather than estimates. The international coordination of this transition was remarkable, though not without challenges.

Different jurisdictions moved at different speeds, creating temporary basis risks for multinational corporations and banks operating across borders.

What are the Repo Markets that Underlie SOFR?

The repo market is a short-term lending market where institutions borrow cash by pledging securities as collateral, then repurchase those securities the next day.

The three segments underlying SOFR serve different market participants:

1. Tri-Party repo involves a third-party custodian bank facilitating transactions between cash lenders (like money market funds) and securities borrowers (typically broker-dealers). This segment represents the largest portion of SOFR’s calculation base.
2. General Collateral Finance (GCF) repo market allows broker-dealers to borrow and lend among themselves intraday and overnight using securities held at a clearing bank.
3. FICC bilateral repo captures transactions cleared through the Fixed Income Clearing Corporation, involving a broader range of participants including hedge funds and asset managers.

Together, these three segments create a comprehensive view of overnight Treasury financing costs across the financial system, making SOFR a representative benchmark of funding conditions.

How is SOFR Calculated?

Understanding the current SOFR rate requires knowledge on how it’s calculated. The Federal Reserve Bank of New York computes SOFR using transaction data from the three repo market segments discussed above.

The calculation uses a volume-weighted median of these transactions, making it resistant to outliers.

Here’s a simplified scenario showing how the calculation works:

The rate is published at approximately 8:00 a.m. Eastern Time on each business day, reflecting the previous business day’s transactions.

The robust calculation methodology means the rate is based on roughly $1 trillion in daily transactions, providing a level of reliability that LIBOR could never match

Here’s a simplified example of how the volume-weighted median works:

In this scenario, with $1 trillion total volume, the median point falls at $500 billion. Transaction C includes this median point, so SOFR would be set at 5.31%. The actual daily calculation involves thousands of transactions, making the process more complex.

Organisations needing historical SOFR data and analytics can leverage Parameta Solutions’ Benchmarks & Indices offering timely and reliable information.

What Drives Supply and Demand in the Repo Markets That Underlie SOFR?

Supply and demand dynamics in repo markets respond to multiple factors. The main drivers of the repo markets are cash borrowers and cash lenders.

On the supply side: The Money market funds (abbreviated to MMF), corporate treasurers, and foreign official institutions provide cash seeking safe overnight returns. When these entities have excess cash, perhaps due to seasonal tax payments or federal operations, repo rates tend to decline.

Conversely, regulatory requirements like Basel III liquidity coverage ratios influence how much banks are willing to pay for overnight funding. Demand for repo financing comes primarily from broker-dealers needing to fund their Treasury securities inventories and market-making activities. Quarter-end and year-end periods often see significant rate volatility as banks reduce balance sheets for regulatory reporting. Federal Reserve operations, particularly quantitative easing or tightening programs, dramatically affect repo market conditions.

During the September 2019 repo rate spike, overnight rates briefly jumped above 5% when regulatory and settlement timing factors created unexpected demand, demonstrating how quickly these markets can tighten.

Additionally, SOFR averages, simple averages of daily SOFR over a period, provide another calculation method. Each convention has trade-offs between simplicity, forward visibility, and how closely it tracks actual overnight funding costs. Institutions must carefully select which SOFR convention aligns with their operational capabilities and customer needs.

What are the benefits of SOFR?

The transition from LIBOR to SOFR reflects a broader move towards a more transparent, transaction-based benchmark. Compared with LIBOR, SOFR offers several important benefits, particularly in terms of stability, security, and the reduction of benchmark manipulation risk.

• Greater stability and reliability: SOFR is generally described as a near risk-free rate, which makes it more stable than LIBOR. Because it is not built on bank credit assumptions, it is less vulnerable to shifts in perceived bank solvency.
• More secure underlying structure: SOFR is based on transactions secured by U.S. Treasury securities. This collateralised basis makes it more secure than LIBOR and supports confidence in the rate’s underlying market during normal financial conditions.
• Removes LIBOR’s credit and liquidity premia: Unlike LIBOR, SOFR does not embed bank credit and liquidity risk. This reduces distortions caused by changing funding conditions and makes the benchmark a cleaner reference rate for many financial contracts.
• Based on real market transactions: SOFR is calculated using actual overnight borrowing transactions rather than estimates submitted by banks. This makes it more transparent, more representative of market activity, and less susceptible to manipulation than LIBOR.

Despite its strengths, SOFR has several important limitations. These arise from its overnight, secured structure and from the way it behaves under financial stress, which can make it less comparable to LIBOR in some uses.

• Lack of a forward-looking term structure: As an overnight rate, SOFR does not naturally provide forward-looking term rates like LIBOR. This makes it less convenient for financial products where borrowers and lenders need payment amounts known in advance.
• Term SOFR may be less robust: Term SOFR helps overcome this issue, but it is derived from derivatives markets rather than the deeper overnight cash market. This may make it less reliable during periods of market stress or reduced liquidity.
• Does not reflect bank credit risk: Because SOFR is secured by U.S. Treasury collateral, it does not capture bank credit risk. This can make it less suitable for pricing products linked to unsecured bank funding conditions.
• Different behaviour during financial stress: SOFR can behave very differently from LIBOR during crises. In March 2020, for example, SOFR fell while credit spreads widened elsewhere, creating a disconnect between benchmark rates and actual funding pressures.
• Challenges for risk management and hedging: differences mean institutions cannot simply replace LIBOR with SOFR without adjustment. Risk models, valuation methods, and hedge strategies based on LIBOR’s historical behaviour may need substantial recalibration.

Contact Parameta Solutions

SOFR is now the key benchmark rate for U.S. dollar markets, replacing LIBOR with a more transparent and transaction-based alternative. As a secured overnight rate, it reflects the cost of borrowing cash against U.S. Treasury securities and is calculated using a volume-weighted median of real repo market transactions.

Understanding what SOFR is, how it works, and how it is calculated is therefore essential for anyone dealing with modern benchmark-linked instruments.

At Parameta Solutions, we understand the data and operational challenges that come with benchmark reform and the shift from LIBOR to SOFR. Our capital markets solutions provide the reference rate data, market insight, and analytics infrastructure firms need to better understand SOFR, support valuation processes, and manage benchmark-linked exposures with confidence.

If you are looking to strengthen your approach to SOFR-based instruments, improve benchmark data access, or enhance risk and pricing workflows, we would be glad to discuss how our data solutions can support your specific requirements. Reach out to our team to learn more.