SOFR

SOFR, the Secured Overnight Financing Rate, is a broad measure of the cost of borrowing cash overnight when the loan is collateralized by U.S. Treasury securities. The Federal Reserve Bank of New York calculates SOFR from transaction data in major Treasury repurchase agreement markets and publishes it each U.S. business day.

SOFR is the preferred alternative to U.S. dollar LIBOR for many loans, bonds, securitizations, derivatives, and valuation processes. It is an overnight wholesale funding benchmark, not a consumer lending rate or a complete borrowing rate by itself.

Key Takeaways

• SOFR is based on secured overnight Treasury repo transactions, not unsecured bank submissions.
• The New York Fed calculates it as a volume-weighted median, not a simple average.
• The daily rate describes one overnight funding day; longer contracts need an average, daily compounding, an index method, or a separately administered term rate.
• SOFR contains much less direct bank-credit risk than LIBOR, so legacy fallbacks may add a fixed spread adjustment.
• A loan’s contractual margin is separate from any LIBOR transition adjustment.
• Treasury collateral does not make a SOFR-linked loan, bond, or derivative risk-free.
• Repo-market conditions can create daily volatility that is smoothed differently by averages and compounded conventions.
• The governing document must specify rate form, observation dates, day count, floor, margin, fallback, and payment timing.

What Transactions Underlie SOFR

SOFR combines transaction data from several segments of the overnight Treasury repo market. The New York Fed states that it includes:

• tri-party Treasury repo transactions
• General Collateral Finance Repo transactions
• eligible bilateral Treasury repo transactions centrally cleared through FICC’s Delivery-versus-Payment service

The bilateral data are filtered to remove a portion of transactions considered specials, where a participant accepts a lower cash return to obtain a particular Treasury security.

SOFR therefore measures the price of overnight cash secured by Treasury collateral. It is not the Treasury yield, the federal funds rate, or the interest rate the Federal Reserve pays on reserve balances.

How SOFR Is Calculated and Published

The New York Fed calculates SOFR as the volume-weighted median transaction rate. Conceptually, transactions are ordered by rate and the published rate is associated with the 50th percentile of cumulative transaction volume.

This differs from:

• a simple average, where each transaction receives equal weight
• a volume-weighted mean, where extreme rates can influence the arithmetic result
• a panel estimate, where banks submit judgment-based borrowing rates

SOFR for the prior business day’s transactions is normally published at approximately 8:00 a.m. Eastern Time. The New York Fed also publishes transaction volume and percentile information, subject to its data-contingency rules.

Daily SOFR, Averages, Index, and Term SOFR

These forms can produce different payments. A document that says only “SOFR” is incomplete unless its definitions identify which form applies.

Calculating With the SOFR Index

If a contract permits the New York Fed’s SOFR Index, a simplified compounded return between valid dates is:

The annualized rate still depends on the contract’s day-count convention and dates. An index ratio cannot replace a specified daily-compounding method unless the agreement allows it.

Worked Example: SOFR-Linked Business Loan

Assume a USD 10 million loan uses compounded SOFR plus a 1.75% margin. For a 90-day Actual/360 interest period, suppose the correctly calculated annualized compounded SOFR is 5.10%.

The annualized all-in rate is:

Illustrative interest is:

This example assumes the compounded benchmark has already been calculated. A real amount depends on daily observations, weekend weighting, lookback or observation shift, floor, rounding, payment delay, and fees.

SOFR Compared With Other Dollar Rates

A change in one rate does not imply an equal change in every other rate. Market structure and contract design matter.

Transition From U.S. Dollar LIBOR

Replacing LIBOR with SOFR changed more than the rate label:

• unsecured term funding became secured overnight funding
• one period-start fixing often became daily observations or another SOFR form
• fallback spreads addressed part of the historical LIBOR-SOFR difference
• payment systems needed new calendars and compounding logic
• loans and hedges needed aligned conventions

Some legacy contracts use Term SOFR, some use SOFR averages, some use compounded SOFR, and some are governed by statutory replacement rules. No universal fallback should be inferred from the product name alone.

How to Review a SOFR Contract

1. Confirm the administrator and exact SOFR form.
2. Identify the accrual and observation periods.
3. Check lookback, observation shift, lockout, and holiday weighting.
4. Verify Actual/360 or another day-count convention.
5. Separate the SOFR rate, transition adjustment, and contractual margin.
6. Determine whether a floor applies before or after adding spreads.
7. Confirm rounding and payment-delay rules.
8. Read temporary and permanent fallback provisions.
9. Compare conventions with any related hedge.
10. Preserve daily-rate or index evidence used in the calculation.

Risks and Limitations

• Basis risk: Different SOFR forms or observation conventions can diverge.
• Timing risk: Compounded-in-arrears interest becomes final near period end.
• Repo-market risk: Collateral supply, dealer balance sheets, and settlement pressures can affect daily SOFR.
• Operational risk: Calendar, compounding, and data errors can change payments.
• Transition risk: A spread adjustment may not perfectly preserve contract economics.
• Floor risk: Applying a floor at the wrong stage changes the all-in rate.
• Instrument risk: A SOFR-linked security still has credit, liquidity, duration, and market-price risk.

Common Mistakes

• Calling SOFR an unsecured interbank lending rate.
• Calculating SOFR as a volume-weighted average instead of a median.
• Using one daily SOFR print for an entire quarter.
• Treating Term SOFR, SOFR Average, and compounded SOFR as interchangeable.
• Assuming Treasury collateral guarantees a linked investment or borrower.
• Comparing a LIBOR margin directly with a SOFR margin without checking transition adjustments.
• Adding the fallback spread twice.
• Ignoring weekend day weights, floors, and observation shifts.

Authoritative Sources

• Federal Reserve Bank of New York: SOFR data and methodology
• Federal Reserve Bank of New York: Additional reference-rate information
• Federal Reserve Bank of New York: SOFR Averages and Index
• Federal Reserve Bank of New York: Alternative Reference Rates Committee

Related Terms

• Alternative Reference Rates: Broader category of post-IBOR benchmarks and transition conventions.
• LIBOR: Discontinued benchmark replaced by SOFR in many U.S. dollar contracts.
• €STR: Unsecured euro overnight benchmark.
• Overnight Rate: One-business-day funding-rate concept underlying SOFR.
• Overnight Index Swap: Derivative that can exchange a fixed rate for compounded SOFR.
• Basis Point: One-hundredth of a percentage point, used for margins and adjustments.

FAQs

This article provides general financial education, not personalized borrowing, investment, accounting, or legal advice. Use the governing contract and current New York Fed publications for operational calculations.