SOFR and LIBOR differ in nearly every way a benchmark rate can differ. SOFR, the Secured Overnight Financing Rate, is a single overnight rate built on roughly $3.3 trillion in daily U.S. Treasury repo transactions. LIBOR, the London Interbank Offered Rate, was a set of forward-looking term rates derived from estimates submitted by a panel of banks about the cost of unsecured borrowing between them. That one structural gap drives every other difference: how each rate handles credit risk, how interest accrues on a loan tied to it, how resistant the benchmark is to manipulation, and how much you know about your payment before the period begins. The remaining U.S. dollar LIBOR settings officially ceased on June 30, 2023, and every contract that once referenced LIBOR now references SOFR or a similar replacement.1FDIC. Joint Statement on Completing the LIBOR Transition
Secured Treasury Repo vs. Unsecured Interbank Lending
LIBOR measured the cost of unsecured borrowing between banks. No collateral changed hands. If the lending bank guessed wrong about the borrower’s creditworthiness, it had no fallback asset. That made LIBOR sensitive to how confident banks felt about each other on any given day, and during financial crises, that confidence evaporated quickly.
SOFR measures something fundamentally different: the cost of borrowing cash overnight against U.S. Treasury securities as collateral. These are repurchase agreements, or repos. A firm sells a Treasury bond to a counterparty today with a binding agreement to buy it back tomorrow at a slightly higher price. The difference is the interest. If the borrower fails to repay, the lender keeps the Treasury bond, which is backed by the U.S. government. That collateral layer virtually eliminates the risk of loss to the lender.2Federal Reserve Bank of New York. How SOFR Works
The Treasury repo market also dwarfs the interbank lending market LIBOR tried to measure. Daily transaction volumes underlying SOFR run around $3.3 trillion.3Federal Reserve Bank of New York. Secured Overnight Financing Rate Data That depth makes the rate hard to push around and gives it something LIBOR eventually lost: a large volume of actual trades to rest on.
Real Transactions vs. Bank Estimates
LIBOR worked by asking a panel of major banks each morning what rate they could borrow at from another bank. The banks submitted estimates, outliers were trimmed, and the remaining numbers were averaged. When real interbank lending was plentiful, the estimates could be checked against actual market activity. When trades thinned out, submissions floated free of any anchor.
That room to shade the number became a scandal. Between 2005 and 2009, traders at multiple banks coordinated to push LIBOR submissions in directions that benefited their trading positions. Barclays alone paid $460 million in penalties after admitting its traders routinely requested favorable submissions and, during the 2007–2009 financial crisis, management directed submitters to lower the bank’s reported borrowing costs to avoid the appearance of weakness.4U.S. Department of Justice. Barclays Bank PLC Admits Misconduct Related to Submissions for LIBOR and EURIBOR Total fines across all implicated banks ran into the billions.
SOFR eliminates the estimation layer entirely. The Federal Reserve Bank of New York collects completed transaction data from three segments of the Treasury repo market: the tri-party repo market, the General Collateral Finance repo market, and bilateral Treasury repos cleared through the Fixed Income Clearing Corporation.3Federal Reserve Bank of New York. Secured Overnight Financing Rate Data Every trade used in the calculation actually happened. No one is asked what they think the rate should be.
The rate is computed as a volume-weighted median of those transactions. You line up trades from lowest to highest rate, walk through the cumulative dollar volume, and take the rate at the midpoint. Using the median rather than a simple average makes the calculation resistant to outliers. The New York Fed publishes SOFR each business day at approximately 8:00 a.m. Eastern along with total transaction volume and selected percentile data.5Federal Reserve Bank of New York. An Updated Users Guide to SOFR Manipulating a rate built on trillions of dollars in completed trades would mean moving the market itself.
Overnight Rate vs. Forward-Looking Terms
LIBOR came in multiple tenors: overnight, one-month, three-month, six-month, and twelve-month. Each was forward-looking. If you had an adjustable-rate mortgage tied to three-month LIBOR, you knew on the first day of each period exactly what your rate would be for the next 90 days. That certainty made cash-flow planning straightforward.
SOFR is a single overnight rate. It tells you what it cost to borrow cash last night, not what it will cost tomorrow. To build the longer horizons that loans and bonds require, the market uses two approaches.
Compounded SOFR in Arrears
Many institutional contracts, and all derivatives that transitioned from LIBOR through ISDA protocols, use daily SOFR compounded over the interest period. Each day’s overnight rate is collected, compounded together, and the interest payment is calculated at the end of the period. You pay for exactly what happened in the market. The trade-off is that you don’t know your final payment until the period is almost over. Most contracts build in a short lookback or payment delay of a few business days so the calculation can be processed before payment is due.
Forward-Looking Term SOFR
The CME Group publishes forward-looking Term SOFR for one-month, three-month, six-month, and twelve-month tenors. These are derived from SOFR futures prices and function much like the old LIBOR terms: you know the rate at the start of the period. The Alternative Reference Rates Committee initially recommended Term SOFR primarily for business loans, trade finance, and certain securitizations where borrowers need payment certainty up front. Using Term SOFR requires a license from CME. The ARRC has encouraged the market to limit its use to contexts where a backward-looking rate genuinely doesn’t work, since compounded SOFR in arrears is the purer reflection of overnight funding costs.5Federal Reserve Bank of New York. An Updated Users Guide to SOFR
Credit Risk and the Spread Adjustment
Because LIBOR was unsecured, it baked in a credit risk premium. That premium reflected the market’s collective judgment about how risky it was to lend to a major bank without collateral. In calm markets the premium was small. During a crisis it could spike by hundreds of basis points in weeks. Borrowers with LIBOR-linked loans saw their costs rise not because the underlying cost of money changed, but because banks became nervous about each other.
SOFR strips that out. Since every transaction is collateralized by Treasuries, the rate reflects only the time value of money, not the creditworthiness of any private institution. Under normal conditions, SOFR runs noticeably lower than LIBOR did for equivalent periods. That gap is exactly why a straight one-for-one swap from LIBOR to SOFR without adjustment would have handed a windfall to borrowers at the expense of lenders, or vice versa depending on the contract.
To keep legacy contracts economically neutral through the transition, the ARRC recommended fixed spread adjustments added on top of SOFR. These adjustments were calculated using a five-year historical median of the difference between LIBOR and SOFR at each tenor. The full set for non-consumer contracts is:6Federal Reserve Bank of New York. ARRC Recommended Fallbacks for USD LIBOR
- Overnight LIBOR: 0.00644%
- One-month LIBOR: 0.11448%
- Three-month LIBOR: 0.26161%
- Six-month LIBOR: 0.42826%
- Twelve-month LIBOR: 0.71513%
These are static numbers, locked in permanently. They do a reasonable job of bridging the average gap between LIBOR and SOFR over a normal cycle, but they cannot replicate the way LIBOR’s credit component would have surged during a banking crisis. That’s the structural trade-off. The point of SOFR is to remove the unpredictable credit-risk spikes that made LIBOR volatile when the banking sector was under stress. Borrowers with SOFR-linked loans won’t see their rates jump just because bank balance sheets look shaky.
What the Difference Means If You Have a Legacy LIBOR Loan
Adjustable-rate mortgages, home equity lines of credit, and private student loans that once referenced LIBOR have already been moved to a replacement. Trillions of dollars in legacy contracts referenced LIBOR, and many were written before anyone anticipated the benchmark would disappear. Congress addressed the gap by passing the Adjustable Interest Rate (LIBOR) Act, signed into law on March 15, 2022 and codified at 12 U.S.C. § 5801 through § 5806.7Office of the Law Revision Counsel. 12 USC 5801 – Findings and Purpose Where a LIBOR contract had no workable fallback provisions, the Board-selected benchmark replacement (SOFR plus the applicable spread adjustment) stepped in automatically on the LIBOR replacement date, and the switch was protected from being treated as a breach or default.8Office of the Law Revision Counsel. 12 USC Ch. 55 – Adjustable Interest Rate (LIBOR)
On the consumer side, Regulation Z required lenders to give written notice at least 15 days before changing the index on a variable-rate loan.9eCFR. Supplement I to Part 1026 – Official Interpretations The CFPB requires lenders to demonstrate that any replacement index is comparable to the original LIBOR index. For adjustable-rate mortgages, that means analyzing whether the two indexes move in similar directions over time, produce comparable payment impacts, and have comparable rate levels once the spread adjustment is applied. The replacement must also be publicly available and outside the lender’s control.10Consumer Financial Protection Bureau. LIBOR Transition FAQs For home equity lines of credit, the standard is that the replacement index must have historical fluctuations “substantially similar” to the LIBOR index being replaced.
In practical terms, your monthly payment after the transition should land close to what it would have been under LIBOR, assuming the spread adjustment was applied correctly. If you see a sudden jump in your rate that doesn’t correspond to broader market movements, request a written explanation from your servicer showing the new index value, the spread adjustment, and the margin used in your calculation. A properly executed transition changes the plumbing behind your rate, not the size of your payment.