What Is the LIBOR Index and How Does It Impact Mortgage Rates Today?
The London Interbank Offered Rate (LIBOR) was the world’s most widely used interest rate benchmark for decades. But LIBOR was officially discontinued on June 30, 2023, after a series of manipulation scandals and regulatory concerns. In 2026, most former LIBOR-linked mortgages have transitioned to a new benchmark called the Secured Overnight Financing Rate (SOFR). This guide explains what LIBOR was, why it was discontinued, and how the transition to SOFR affects mortgage rates today.
Written by: John Tappan, NMLS #394171 | Fact-Checked ✓
What Was the LIBOR Index?
LIBOR was created in 1986 as a benchmark interest rate. It represented the average rate at which major London banks would lend to each other for short-term loans. LIBOR was calculated in five currencies (U.S. dollar, euro, British pound, Japanese yen, and Swiss franc) across seven maturities (from overnight to 12 months). At its peak, LIBOR served as the reference rate for approximately $350 trillion in financial contracts worldwide, including mortgages, corporate loans, derivatives, and student loans.
Why LIBOR Was Discontinued
Between 2008 and 2012, investigations revealed widespread LIBOR manipulation by major banks. Traders at banks including Barclays, UBS, Deutsche Bank, and Royal Bank of Scotland were caught submitting false interest rate quotes to benefit their own trading positions. Regulators imposed billions of dollars in fines. The scandals damaged trust in LIBOR as a fair benchmark.
Beyond the manipulation issues, LIBOR faced structural problems. It was based on estimates rather than actual transactions. As the interbank lending market shrank after the 2008 financial crisis, fewer real transactions supported LIBOR calculations. In 2017, the UK Financial Conduct Authority (FCA) announced that it would stop compelling banks to submit LIBOR quotes after 2021. Most LIBOR settings ceased publication on December 31, 2021. The most-used U.S. dollar LIBOR settings ended June 30, 2023.
The Transition to SOFR
The U.S. mortgage industry transitioned from LIBOR to the Secured Overnight Financing Rate (SOFR). SOFR is based on actual transactions in the U.S. Treasury repurchase agreement (repo) market. Unlike LIBOR, SOFR reflects real transactions, making it much harder to manipulate.
The Federal Reserve’s Alternative Reference Rates Committee (ARRC) recommended SOFR as the primary replacement for U.S. dollar LIBOR. The Federal Reserve Bank of New York began publishing SOFR in April 2018. As of September 18, 2026, the overnight SOFR rate was approximately 3.85%. The 30-day SOFR average was approximately 3.65%.
How LIBOR-to-SOFR Transition Affected Mortgages
Millions of adjustable-rate mortgages (ARMs) and home equity lines of credit (HELOCs) originally used LIBOR as their benchmark. During the transition, these loans moved to SOFR or another replacement index.
For most consumer loans, the transition included a “spread adjustment” that made the replacement rate roughly equivalent to LIBOR. This spread adjustment was designed to prevent borrowers from facing sudden payment changes just from the benchmark switch. The specific adjustment depended on the LIBOR tenor being replaced:
- 1-Month LIBOR to 1-Month CME Term SOFR: +11.4 basis points
- 3-Month LIBOR to 3-Month CME Term SOFR: +26.2 basis points
- 6-Month LIBOR to 6-Month CME Term SOFR: +42.8 basis points
- 12-Month LIBOR to 12-Month CME Term SOFR: +71.5 basis points
SOFR Behavior in 2026
Following the Federal Reserve’s September 16, 2026 rate hike (first Fed hike since 2023), SOFR increased as expected. SOFR closely tracks Federal Reserve policy decisions because it reflects the market for overnight loans backed by U.S. Treasury securities. When the Fed raises its target rate, SOFR rises. When the Fed lowers its target rate, SOFR falls.
This close Fed relationship makes SOFR predictable for lenders and borrowers. Adjustable-rate mortgage borrowers can watch Fed announcements to anticipate SOFR movements. Explore rate-and-term refinance considerations for borrowers thinking about converting from ARM to fixed-rate loans.
Legacy LIBOR Loans
Some financial contracts still reference LIBOR through fallback provisions. Federal legislation (the Adjustable Interest Rate Act, signed March 2022) provided a legal framework for automatically transitioning tough LIBOR contracts to SOFR-based rates. This law protected borrowers and lenders from ambiguity in contracts that didn’t specify what would happen when LIBOR ended.
Most consumer mortgages that originally used LIBOR have now transitioned to SOFR. Borrowers can check their current index by reviewing their loan documents or contacting their servicer.
Frequently Asked Questions
When was LIBOR discontinued?
Most LIBOR settings were discontinued on December 31, 2021. The most-used U.S. dollar LIBOR tenors (1-month, 3-month, 6-month, and 12-month) continued until June 30, 2023, then permanently ceased. The 1-week and 2-month U.S. dollar LIBOR tenors ended on December 31, 2021. The UK Financial Conduct Authority allowed some “synthetic” LIBOR rates for limited transition purposes but these have also mostly wound down. In September 2026, LIBOR is effectively dead as an active benchmark rate.
What replaced LIBOR for U.S. mortgages?
The Secured Overnight Financing Rate (SOFR) replaced LIBOR as the primary benchmark for U.S. dollar loans and derivatives. SOFR is based on actual transactions in the U.S. Treasury repurchase market and is administered by the Federal Reserve Bank of New York. Unlike LIBOR, SOFR reflects real overnight lending transactions rather than bank estimates. Some other benchmarks exist for specific markets (BSBY, Ameribor), but SOFR dominates the U.S. mortgage market. The Alternative Reference Rates Committee formally recommended SOFR as the LIBOR replacement.
How did LIBOR-to-SOFR transition affect my ARM or HELOC?
Most adjustable-rate mortgages and HELOCs that originally used LIBOR have transitioned to SOFR with a “spread adjustment” that made the effective rate approximately equal to the LIBOR rate. The specific spread depends on which LIBOR tenor your loan used. For example, 1-month LIBOR loans got a +11.4 basis point spread adjustment when moving to 1-month SOFR. This adjustment prevented sudden payment changes just from the benchmark switch. Your loan documents should specify the exact replacement rate structure.
How does the September 2026 Fed hike affect SOFR?
The Federal Reserve raised its target federal funds rate by 0.25 percentage points on September 16, 2026, the first Fed hike since 2023. This directly affected SOFR because SOFR reflects overnight lending markets that closely follow Fed policy. Following the hike, overnight SOFR increased to approximately 3.85% (as of September 18, 2026). The 30-day SOFR average was approximately 3.65%. Borrowers with SOFR-based ARMs and HELOCs saw their rates increase accordingly.
Are there still any LIBOR-based mortgages in 2026?
Very few active LIBOR-based mortgages exist in 2026. Most mortgages have transitioned to SOFR through automatic contract fallback provisions or through the federal Adjustable Interest Rate Act of 2022 (also called LIBOR Act). Some older loans with “hard-wired” LIBOR provisions may still reference LIBOR through fallback language that specifies alternate rates. Check your loan documents or contact your servicer if you have questions about which index your loan uses. Learn more via complete refinance mortgage program options for borrowers wanting to convert to fixed rates.
Sources: Alternative Reference Rates Committee (ARRC); Federal Reserve Bank of New York (SOFR data); UK Financial Conduct Authority (LIBOR wind-down announcements); Adjustable Interest Rate Act (2022).
- BD Nationwide Mortgage is not a lender. Our website connects homeowners with brokers, lenders, banks and credit unions and does not directly originate home loans or HELOCs.