Interest Rate Swaps Explained: Comparative Advantage & Example

Interest rate swaps are explicitly named on ACCA Advanced Financial Management (AFM), under the use of financial derivatives to hedge interest rate risk. They're one of the more approachable derivatives topics because the underlying logic — two parties trading interest obligations to each get a better deal than either could alone — is genuinely intuitive once the comparative advantage argument clicks.

What is an interest rate swap?

An interest rate swap is an agreement between two parties to exchange interest payment obligations on a notional amount of debt, usually via a bank as intermediary. Typically one party swaps from paying a fixed rate to effectively paying a floating rate, while the other swaps the opposite way — from floating to effectively fixed. No principal changes hands; only the interest payment streams are exchanged, which is why it's classed as an off-balance-sheet derivative rather than a new borrowing.

Companies use swaps for two main reasons: to hedge existing interest rate exposure (a company with floating-rate debt that's worried rates will rise can swap into an effectively fixed rate), or to access cheaper finance than either party could get by borrowing directly in their preferred market.

Why two companies would bother swapping: comparative advantage

The classic AFM scenario involves two companies with different credit standing, each quoted different borrowing rates in both the fixed and floating markets. The key insight — directly analogous to comparative advantage in trade theory — is that even if one company can borrow more cheaply in both markets, a gain from swapping is still available if the size of its advantage differs between the two markets.

Take two companies: Company A can borrow fixed at 8% or floating at LIBOR + 1%. Company B, a lower-rated borrower, can only borrow fixed at 11% or floating at LIBOR + 2%. Company A is cheaper in both markets in absolute terms — but its advantage in the fixed market (3 percentage points: 11% − 8%) is much bigger than its advantage in the floating market (1 percentage point: (LIBOR+2%) − (LIBOR+1%)). Company B, in other words, has a comparative advantage in the floating market, even though it doesn't have an absolute one.

How the gain is calculated and split

The total potential gain from swapping equals the difference between the two companies' fixed-rate spread and their floating-rate spread: 3% − 1% = 2% per year, in this example. Each company borrows in the market where it has the comparative advantage — Company B borrows floating, Company A borrows fixed — and they then swap their interest obligations, usually arranged and guaranteed by a bank, which takes a fee for the service (commonly split evenly between the two parties, e.g. 0.5% each).

After the bank's fee is deducted, the remaining 1% gain (2% total minus 0.5% + 0.5% fee) is typically split evenly between the two companies, 0.5% each. The net result: Company A ends up paying LIBOR + 0.5% instead of the LIBOR + 1% it could have borrowed at directly, and Company B ends up paying 10.5% instead of the 11% it would have paid borrowing fixed directly — both parties are better off than if they'd each simply borrowed in their own preferred market without swapping.

What AFM questions actually test

Beyond identifying which company has the comparative advantage in which market, AFM questions typically ask students to calculate the total gain available, decide a reasonable split (often stated in the question, sometimes requiring a 50/50 assumption), and set out each company's final effective borrowing cost after the swap and any intermediary fee. Some questions also test the hedging use case directly — a company with existing floating debt wanting to lock in a fixed cost ahead of an expected rate rise — rather than the comparative-advantage borrowing scenario.

Swaps versus a straightforward direct loan

It's worth being clear that a swap doesn't change who a company's actual lender is — Company A still owes its fixed-rate debt to its original lender, and Company B still owes its floating-rate debt to its own lender. The swap sits alongside those loans as a separate contract that exchanges only the net interest cash flows between the two companies (via the bank). This is exactly why credit risk still matters in a swap: if one party in the arrangement defaults, the other is still legally on the hook for its own original loan, even though the economic benefit of the swap has disappeared. AFM questions occasionally test this counterparty-risk point directly, alongside the mechanical gain calculation.

FAQs

Does an interest rate swap involve exchanging the underlying loan principal?
No — only the interest payment obligations are swapped. The notional principal is used purely to calculate the interest amounts; it's never actually exchanged, which is why swaps don't appear as new borrowing on the balance sheet.

What's the difference between hedging with a swap and hedging with other interest rate derivatives like FRAs or options?
A swap typically hedges a longer-term, ongoing exposure by converting the whole interest rate basis (fixed to floating or vice versa) for the life of the swap, whereas forward rate agreements and interest rate options are usually used for shorter, more specific hedging periods or when the company wants to retain some upside potential.

Which ACCA paper examines interest rate swaps?
ACCA AFM, under the use of financial derivatives to hedge against interest rate risk — alongside the closely related currency swap topic used to hedge foreign exchange risk.