Interest Rate Swap (IRS) explained
By Ken Chigbo, Founder, KenMacro. Published 2026-05-13.
Quick answer
An interest rate swap is a derivative contract where two counterparties exchange streams of interest payments on a notional principal. One leg pays a fixed rate, the other pays a floating rate tied to a benchmark such as SOFR or EURIBOR. The notional itself is never exchanged, only the net interest cash flows on each settlement date.
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What is interest rate swap?
An interest rate swap, commonly abbreviated to IRS, is a bilateral derivative contract in which two parties agree to exchange interest payment streams calculated on an agreed notional principal over a defined term. The most common structure is the plain vanilla swap, where one counterparty pays a fixed coupon and receives a floating rate, while the other does the reverse. Floating legs are referenced to overnight benchmarks such as SOFR in the US, SONIA in the UK, or ESTR in the eurozone. Tenors range from a few months to thirty years or longer, and the notional is purely a calculation device, not an amount that changes hands.
How traders use interest rate swap
Retail forex traders rarely transact swaps directly, but the desk treats the swap curve as one of the cleanest reads on forward rate expectations. The two year and five year swap rates effectively price what the market thinks the central bank will do, and currency pairs respond mechanically to shifts in swap rate differentials. When the two year USD swap rate rises relative to its EUR equivalent, EUR/USD tends to grind lower over the medium term. Institutional desks use IRS to hedge bond portfolios, lock in funding costs, or express macro views on the path of policy rates without taking duration risk in cash bonds. Cross currency basis swaps, a related instrument, also signal stress in dollar funding markets.
Worked example of an interest rate swap
Consider a corporate that has issued a floating rate bond paying SOFR plus 150 basis points on a 100 million notional. The treasurer wants certainty on funding costs and enters a five year IRS where the corporate pays a fixed 4 percent and receives SOFR. The floating receipts from the swap offset the floating payments on the bond, leaving the corporate with an effective fixed cost of 4 percent plus the 150 basis point spread, so 5.5 percent. The swap counterparty, often a dealer bank, will typically hedge the resulting position in the underlying rates market.
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Frequently asked
What is the difference between an interest rate swap and a forex swap?
An interest rate swap exchanges fixed for floating interest payments in a single currency on a notional principal that never changes hands. A forex swap is a short dated agreement to exchange two currencies on one date and reverse the trade on a later date at a pre agreed rate, primarily used to manage funding and roll spot positions. The two instruments address different risks and trade in different markets.
Why do swap rates matter for currency traders?
Swap rates encode the market’s forward expectation of central bank policy more cleanly than government bond yields, which carry credit and liquidity premia. The desk monitors two year swap rate differentials between currency pairs because these differentials track medium term currency direction well. A widening spread in favour of one currency typically attracts capital flows and supports that currency, though the relationship is noisy in the very short term.
Who uses interest rate swaps?
End users include corporates hedging issued debt, pension funds and insurers matching long dated liabilities, banks managing balance sheet duration, and hedge funds expressing directional or relative value views on rates. Dealer banks intermediate the flow and warehouse residual risk. Since the post 2008 reforms, most standardised swaps are centrally cleared through CCPs such as LCH SwapClear, which has materially reduced bilateral counterparty risk.
What replaced LIBOR as the floating leg benchmark?
Following the LIBOR transition completed by mid 2023, the main floating leg references are now SOFR for US dollar swaps, SONIA for sterling, ESTR for euros, TONA for yen, and SARON for Swiss francs. These are overnight risk free rates compounded in arrears over the relevant payment period, rather than the forward looking term rates that LIBOR provided. The change has reshaped swap conventions and pricing.
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