How Interest Rate Swaps Work: SOFR, ISDA, and Exit Costs

An interest rate swap is a contract in which two parties agree to exchange streams of interest payments calculated on the same reference dollar amount, with one side paying a fixed rate and the other paying a floating rate that resets against a benchmark. Understanding how interest rate swaps work starts with a single point: the reference amount, called the notional principal, never changes hands. Only the net difference between the two interest calculations moves between the parties at each payment date. That structure is what lets a company convert floating-rate debt into a predictable fixed cost, or vice versa, without refinancing the underlying loan.

The Mechanics of a Fixed-for-Floating Swap

Every plain vanilla swap has two legs. The fixed-rate payer owes a set percentage for the life of the contract. The floating-rate payer owes an amount that resets periodically against a benchmark index. Both amounts are applied to the same notional principal, which exists only as a math reference.

At each scheduled payment date, the parties net their obligations. The party owing more sends the difference to the other. Say the notional is $10 million, the fixed leg owes $125,000 for the period, and the floating leg owes $118,000. The fixed-rate payer wires $7,000. That’s it. Cash movement stays small even when the underlying exposure is significant.

The economics track market rates in a straightforward way. When rates rise above the fixed rate, the floating-rate payer owes more and the fixed-rate payer comes out ahead. When rates fall, the fixed-rate payer keeps sending payments calibrated to a higher rate than the market now demands. A company that borrowed at a floating rate and then entered a pay-fixed swap has effectively converted its debt to a fixed cost. The swap doesn’t lower interest expense; it makes the expense knowable.

Terms That Have to Be Nailed Down

A handful of operational details determine how each payment is calculated. Any ambiguity here creates payment discrepancies that are expensive to unwind later.

Notional principal amount. The dollar figure both interest rates are applied to. It doesn’t change hands. For a standard fixed-for-floating swap, the notional stays constant, though some structures let it change over time.
Effective date. The day interest begins accruing under the contract.
Termination date. The day the swap expires.
Payment frequency. How often the parties net and settle. Monthly, quarterly, and semi-annually are the common intervals.
Day count convention. The formula that turns a period into a fraction of a year. U.S. dollar swaps typically use 30/360 for the fixed leg and Actual/360 for the floating leg. Actual/360 counts every calendar day but divides by 360, so a full year of interest slightly exceeds the quoted annual rate.
Floating rate index. The benchmark that resets the floating payment. For new U.S. dollar contracts, this is almost always a variant of SOFR.

The SOFR Benchmark: Term Versus Daily

The Secured Overnight Financing Rate replaced LIBOR as the standard benchmark for U.S. dollar swaps, and the floating side of nearly every new dollar contract references it. But not all SOFR references work the same way.

Term SOFR is published by CME Group in 1-month, 3-month, 6-month, and 12-month tenors, derived from SOFR futures trading. It gives the borrower a known rate at the start of each interest period, similar to how LIBOR worked, which makes cash planning straightforward. Daily SOFR accumulates the actual overnight rate through the period, either simple or compounded in arrears. The exact payment isn’t known until the period ends.

The Alternative Reference Rates Committee has recommended that most cash-market products use overnight SOFR or SOFR averages rather than Term SOFR, reserving the term rate mainly for business loans where the borrower needs the payment amount in advance. The distinction matters for hedging. Term SOFR reflects market expectations about where rates will go; compounded daily SOFR reflects where rates actually went. Hedging a Term SOFR loan with a standard overnight-index swap creates a small basis mismatch, which adds cost. For borrowers who can absorb rate uncertainty within a period, using daily SOFR on both the loan and the swap is cleaner and typically cheaper.

Common Variations

The fixed-for-floating structure is the most traded. Several variations exist for situations where a simple rate exchange doesn’t match the underlying exposure.

Basis swap. Both sides pay floating, but each references a different index or tenor. A company might swap 1-month SOFR payments for 3-month SOFR payments because its assets and liabilities reset on different schedules.
Currency swap. The two legs are denominated in different currencies. Unlike a standard interest rate swap, currency swaps often involve an actual exchange of principal at the start and end of the contract, because the parties need the foreign currency itself.
Amortizing swap. The notional declines on a set schedule, typically matching the paydown of an amortizing loan. Hedging a 10-year term loan with a fixed-notional swap would leave the borrower over-hedged in later years as the loan balance shrinks.
Accreting swap. The notional grows over time. Less common, but useful for construction financing and other situations where the balance builds before it starts to decline.

The ISDA Framework That Governs the Trade

Nearly all interest rate swaps are documented under forms published by the International Swaps and Derivatives Association. Rather than negotiating a fresh contract for every trade, the parties sign a single ISDA Master Agreement covering all transactions between them. Individual trades are then papered through short confirmations that reference the master for the heavy legal lifting.

The master itself is a preprinted form. Customization lives in the Schedule, where parties modify default provisions, add representations, and set thresholds. Collateral arrangements sit in a separate Credit Support Annex, which forms part of the Schedule. The CSA establishes which party posts collateral, what assets qualify, and when transfers occur. On each valuation date, the party whose position is underwater delivers eligible collateral to the other side. If the position reverses, collateral flows back. The CSA also sets a minimum transfer amount so trivial sums don’t move.

Section 5 of the ISDA 2002 Master Agreement defines when one party can pull the plug. It draws a line between an Event of Default, where one side is at fault, and a Termination Event, where external circumstances make performance impossible or uneconomic. The main Events of Default include:

Failure to pay. A missed payment not cured by the next business day after notice.
Breach of agreement. Failing to perform any obligation under the master if not remedied within 30 days after notice, or repudiating the contract.
Credit support default. Failing to perform under the CSA, or the CSA expiring or being terminated without consent.
Misrepresentation. A representation that turns out to have been materially incorrect when made.
Cross-default. If elected in the Schedule, a default on other debt above a specified threshold triggers default under the swap as well.
Bankruptcy. Insolvency, inability to pay debts, a bankruptcy filing, or the appointment of a receiver.
Merger without assumption. A merger or transfer of substantially all assets to an entity that fails to assume the swap obligations.

Termination Events cover illegality, force majeure, and tax events that impose new withholding. When one occurs, the affected transactions can be terminated, not necessarily every transaction under the master. Upon early termination, the non-defaulting party (or, for Termination Events, the non-affected party) calculates a Close-out Amount representing the cost of replacing the terminated transactions at current market rates using commercially reasonable procedures. The final settlement nets unpaid amounts owed by both sides against that close-out value.

What It Costs to Exit Early

This is where most commercial borrowers get surprised. If you entered a pay-fixed swap to hedge a floating-rate loan and you want out early, because you’re refinancing, selling a property, or paying off the loan, you may owe a substantial breakage cost. The amount depends on how far current market swap rates have moved from the fixed rate you locked in.

The math is intuitive. The termination value equals the present value of the remaining fixed-rate payments you promised, minus the present value of what those payments would be at today’s market rate, discounted back to the present. If rates have dropped significantly since you entered the swap, that difference can be large. On a $50 million notional with several years remaining, breakage in the hundreds of thousands is common when rates have fallen.

When rates have risen, the math works the other way. The swap has positive value to you, and the bank owes you money on termination. In practice, borrowers exit swaps more often in falling-rate environments, when refinancing looks attractive, which is precisely when breakage costs are highest.

One wrinkle: the bank’s quoted termination value may not match the theoretical midmarket value. Banks typically apply a spread. If you owe breakage, the quoted cost tends to run higher than midmarket; if the bank owes you, the quoted payment tends to run lower. Dodd-Frank rules require dealers to disclose the midmarket value of the swap, but the actual termination price can still differ. Before accepting a quote, an independent valuation is worth the expense.

Clearing Rules and the End-User Exception

Under the Commodity Exchange Act, it is unlawful to enter into a swap that must be cleared without submitting it to a registered derivatives clearing organization.¹ The specific classes subject to mandatory clearing are listed in CFTC regulations. For U.S. dollar interest rate swaps, the overnight index swap class referencing SOFR or Fed Funds must be cleared for maturities from 7 days to 50 years.²

Jurisdiction sits with the CFTC, not the SEC. The SEC regulates security-based swaps, which are tied to individual securities or narrow-based security indexes and are a different category.

When a swap clears, the clearinghouse interposes itself between the two original counterparties, becoming the buyer to every seller and the seller to every buyer. If one party defaults, the other’s exposure is to the clearinghouse rather than to the failed counterparty directly. Both parties post initial margin as a performance bond, and variation margin is exchanged daily based on the contract’s current market value. Losses can’t accumulate unchecked.

Not every participant has to clear. A counterparty may elect an exception if it meets three conditions: it is not a “financial entity” (a category that includes swap dealers, major swap participants, commodity pools, private funds, and certain banks), it is using the swap to hedge or mitigate commercial risk, and it notifies the CFTC how it meets its financial obligations for non-cleared swaps.¹ The notification can be filed annually or on a swap-by-swap basis.³ Small banks, savings associations, farm credit system institutions, and credit unions with total assets of $10 billion or less are excluded from the financial entity definition and are eligible for the exception on the same footing.

A manufacturing company using an interest rate swap to hedge a floating-rate equipment loan can avoid the cost and operational burden of central clearing by electing this exception. Financial institutions above the asset threshold and entities using swaps for speculation cannot.

Reporting and Tax Treatment

Every swap, cleared or uncleared, must be reported to a registered swap data repository. The obligation falls on the counterparty highest in a defined hierarchy: swap dealers first, then major swap participants, then financial entities, then non-financial end-users.⁴ For off-facility swaps where a swap dealer is a counterparty, which covers most corporate hedging trades, the dealer reports creation data by the end of the next business day after execution. Even non-reporting counterparties have to notify the reporting counterparty of errors within three business days and retain records for the life of the swap plus five years.

The IRS treats interest rate swaps as notional principal contracts. Periodic payments, the regular fixed or floating amounts exchanged at each payment date, are recognized ratably over the accrual period they relate to, regardless of whether you use the cash or accrual method. If the floating rate resets in arrears and the exact amount isn’t known at year-end, you estimate based on the index value on the last day of the taxable year and true up in the following year.⁵

Non-periodic payments, meaning upfront premiums, off-market swap payments, or prepayments of one leg, are spread over the life of the contract rather than recognized when paid. The general rule allocates them in line with forward rates. An alternative method lets taxpayers amortize an upfront payment as if it were the present value of a series of equal payments through the swap term.⁵ The net figure for the year flows into ordinary income or deductions. Swap payments generally don’t produce capital gains or losses unless a termination payment falls outside the notional principal contract rules.

Hedge Accounting Under ASC 815

For financial reporting, a company that wants its swap gains and losses to offset the hedged item on the income statement, rather than flow through earnings independently, must qualify for hedge accounting under FASB’s Accounting Standards Codification Topic 815. At hedge inception, the company documents the hedging relationship, identifies the hedged item and hedging instrument, specifies the risk being hedged, and describes how effectiveness will be assessed.⁶

The relationship must be highly effective at inception and on an ongoing basis. A shortcut method allows a company to assume perfect effectiveness, skipping ongoing quantitative testing, if the swap’s terms closely mirror the hedged debt: same notional as the loan principal, zero fair value at inception, same floating index as the benchmark rate being hedged, and no prepayment features on the debt unless the swap contains a matching option. Missing any of these means the company must run periodic regression analysis or dollar-offset testing. Failing to qualify for hedge accounting doesn’t prevent a company from using swaps. It just means mark-to-market gains and losses hit earnings each period, creating income statement volatility even when the economic hedge is working perfectly.

Before You Sign

The legal and operational setup for a first-time swap counterparty is heavier than most borrowers expect. Negotiating the ISDA Master Agreement, Schedule, and CSA typically requires outside counsel, with legal fees that can run several thousand dollars or more depending on the complexity. Entities transacting in OTC derivatives also need a Legal Entity Identifier, a 20-character code administered through the Global Legal Entity Identifier Foundation, with annual renewal fees that vary by issuer.

The more consequential cost is the one people overlook: breakage exposure. Before signing, run the numbers on what early termination would cost if rates dropped 100, 200, or 300 basis points. If your loan has a prepayment option or you might sell the underlying asset before the swap matures, that scenario analysis isn’t optional. A swap that saves $40,000 a year in interest expense can carry a termination cost many times that amount if rates move sharply against you.

For non-financial companies eligible for the end-user clearing exception, electing it avoids the operational burden of clearing but does not eliminate collateral obligations. Your bank counterparty will still require margin under the CSA, and the terms may be less favorable than what a clearinghouse would impose since they’re bilaterally negotiated. Working through the collateral requirements before execution, including what happens if the mark-to-market moves significantly against you, prevents a liquidity surprise later.

1
Office of the Law Revision Counsel. 7 USC 2 – Jurisdiction of Commission; Liability of Principal for Act of Agent; Commodity Futures Trading Commission; Transaction in Interstate Commerce
2
eCFR. 17 CFR 50.4 – Classes of Swaps Required To Be Cleared
3
Federal Register. End-User Exception to the Clearing Requirement for Swaps
4
eCFR. 17 CFR Part 45 – Swap Data Recordkeeping and Reporting Requirements
5
eCFR. 26 CFR 1.446-3 – Notional Principal Contracts
6
Financial Accounting Standards Board. Accounting Standards Update 2017-12 – Derivatives and Hedging (Topic 815) Targeted Improvements to Accounting for Hedging Activities