Interest Rate Benchmark Reform: LIBOR to SOFR and Risk-Free Rates

Interest rate benchmark reform is the market-wide move from LIBOR to risk-free reference rates — SOFR for the US dollar, SONIA for sterling, €STR for the euro, and their peers — largely complete now. LIBOR was retired because the interbank borrowing it was meant to measure had all but stopped happening, so the rate leaned on bank judgement and was open to manipulation. In its place regulators put transaction-based, near risk-free overnight rates. The concept is simple: swap the benchmark. The work, as always, was in the long tail — legacy contracts, fallback language, system conventions, and getting the interest calculation right under a rate that behaves differently from the one it replaced.

(This is a plain explanation of what benchmark reform changed, not investment or hedging advice for any particular situation.)

Why LIBOR had to go

For decades LIBOR was the reference rate under most floating-rate debt and interest rate risk in corporate treasury. Your loan was quoted as LIBOR plus a margin; your swaps and caps referenced the same LIBOR. It was the rate the whole edifice sat on.

The problem was what LIBOR actually measured: the rate at which a panel of banks estimated they could borrow unsecured from each other. Two things went wrong with that. First, after the financial crisis, banks largely stopped lending to each other unsecured for term — so the transactions the rate was supposed to reflect increasingly weren't there. The number rested more on expert judgement than on trades. Second, a benchmark built on submissions rather than transactions is manipulable, and the rate-rigging scandals proved it was. A benchmark underpinning an enormous stock of contracts couldn't credibly rest on so few real trades and so much judgement. Regulators drew the obvious conclusion and pushed the market onto something anchored in actual transactions.

What replaced it: risk-free rates

The replacements are the risk-free reference rates (RFRs), one per currency, each built on real market transactions:

• SOFR (Secured Overnight Financing Rate) — the US dollar, based on overnight secured borrowing in the Treasury repo market.
• SONIA — sterling.
• €STR — the euro area.
• TONA — Japan.
• SARON — Switzerland.

They're called near risk-free because they're overnight and carry little of the bank-credit risk baked into unsecured interbank lending. Sterling and most non-USD LIBOR settings ended around the end of 2021, and the main USD LIBOR settings ended around mid-2023. RFRs are the standard now — this isn't a coming change to prepare for, it's the world you already operate in.

The differences that actually matter

On paper it's just a different rate. Operationally, the structure is different in ways that reach into every interest calculation.

The one that bites is timing. LIBOR was forward-looking: at the start of an interest period you already knew the rate for it. An RFR is overnight, so a term interest amount is usually built by compounding the daily rate in arrears — you don't know the final figure until close to the payment date. That single change ripples into cash forecasting, invoicing, loan operations and system logic.

Two bridges were needed to make legacy contracts work. Because RFRs are near risk-free and LIBOR carried a credit and term premium, moving an existing contract from one to the other would silently change its economics — so a credit spread adjustment was added to bridge the gap and keep legacy deals roughly whole. And for cases that genuinely need a rate known in advance — some trade finance, some loans where compounding in arrears is impractical — term RFR variants (forward-looking rates derived from RFR derivatives) exist to fill that specific gap.

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The hard part was never picking the new rate. It was that a backward-looking, compounded overnight rate doesn't behave like a forward-looking term rate — and every contract, system and interest calculation had quietly assumed the old behaviour.

What it meant for corporate treasury

If you ran a treasury through this, the transition wasn't a memo — it was a programme of work:

• Repapering. Every LIBOR-referencing loan and derivative needed amending or replacing — new reference rate, fallback language, the credit spread adjustment where relevant. The long tail of old bilateral agreements was the slow part.
• Fallbacks. Contracts needed robust language for what the rate becomes when LIBOR ends — the difference between an orderly switch and a dispute.
• Systems and conventions. Treasury and loan systems had to handle compounding in arrears: lookback periods, observation shifts, day-count and rounding conventions. Small choices that have to match the counterparty's, or the two sides disagree on the interest due.
• Interest calculation. Getting the compounded-in-arrears number right, reconciled against the bank, was the unglamorous core of it — and the place errors actually showed up.
• Hedge relationships. A swap that referenced LIBOR against a loan that now references SOFR is no longer a clean match. Hedge documentation had to be updated and relationships re-checked so they still passed effectiveness testing — the industry-wide reliefs helped, but the work still had to be done.

Docs versus reality

The slide-deck version is one line: replace LIBOR with SOFR. The reality was months of reconciling legacy paper, chasing counterparties for amendments, and arguing with a treasury system about lookback conventions. Nothing about the concept was hard. Everything about the implementation was in the detail — the contracts nobody had looked at in years, the fallback clauses, the exact compounding method, and interest figures that had to tie out to the penny against a bank that had made its own convention choices.

That's the pattern with benchmark reform, and it's the pattern with most treasury change: the decision is trivial and the transition is not. The rate under your interest rate risk is now an RFR, your hedges reference it, and it works. Getting there was a reminder that in treasury the benchmark is never just a number — it's a number wired into every contract, system and calculation you own.

Part of the Treasury Risk Management guide. See also interest rate risk in corporate treasury and what treasury risk management is. The newsletter sends one finance-systems pattern every two weeks.