What it means
In an ordinary interest rate swap one side pays a fixed rate and the other pays a floating rate. In a basis rate swap both legs float, for example one linked to a one-month reference rate and the other to a three-month version of the same rate, or one linked to a domestic benchmark and the other to a foreign one.
These deals exist because of mismatch. A lender might fund itself with three-month borrowing while its loan book reprices monthly, so even though both sides float, the timing difference creates real profit and loss.
Because the two floating rates differ in risk or timing, one leg usually carries a spread. That spread, quoted in basis points, is the price of the mismatch, and it widens sharply whenever short-term credit conditions tighten.
Cross-currency basis swaps are the best-known variant, exchanging floating payments in two currencies and normally the principal at the start and end as well. They became a closely watched indicator after 2008, because a large negative basis signals that borrowers are struggling to obtain a particular currency.
For a corporate treasurer the practical use is narrow but valuable. If revenue is tied to one benchmark and debt to another, a basis swap converts the exposure without touching the underlying loan agreements.
In practice
Real-world examples.
Example
A specialist lender funds itself by issuing three-month commercial paper but writes loans that reprice monthly. It enters a basis rate swap receiving the monthly rate and paying the quarterly one, so that funding cost and loan income move together.
Example
A European corporate borrows in dollars because the bond market is deeper there, then uses a cross-currency basis swap to turn the dollar coupon into a euro floating obligation that matches its revenue.
Example
A bank treasury team watches the spread on a one-month against three-month basis swap widen from 4 to 18 basis points during a period of market stress. The move tells them short-dated funding has become scarce well before it appears in published data.
Formula
Calculation
Net settlement = Notional x (Rate received - Rate paid) x Day-count fraction. No principal is exchanged in a single-currency basis rate swap; only the interest difference changes hands.
A bank enters a basis rate swap on a notional amount of $50,000,000, receiving three-month term SOFR flat and paying one-month SOFR plus 12 basis points. Over one quarter, three-month term SOFR sets at 4.40% while the compounded one-month rate averages 4.32%. The paying leg therefore costs 4.32% + 0.12% = 4.44%, so the net rate is 4.40% - 4.44% = -0.04%. Applying that to the notional for a quarter gives 50,000,000 x 0.0004 x 0.25 = $5,000 payable by the bank. That is a small sum on its own, but the same trade repeated across several billion dollars of notional turns it into a material line in the funding budget.Case study
Seen in the real world.
Ashfield Equipment Finance is a fictional lender invented for this illustrative example. It funded a $50,000,000 leasing book with rolling three-month borrowing while the leases themselves repriced every month against a different short-term benchmark.
For two years the two rates tracked each other closely and nobody paid attention. Then a funding squeeze pushed the three-month rate well above the compounded one-month rate, and the company's interest margin narrowed by around 25 basis points, costing roughly $125,000 a year on that notional for reasons entirely outside its lending decisions.
In this illustrative story the treasurer put a basis rate swap in place to exchange the two floating exposures, accepting a 12 basis point spread as the cost of removing the mismatch. The margin stopped moving with funding conditions, which was the point.
Watch out
Common mistakes.
- Confusing a basis rate swap with a plain interest rate swap, when the defining feature is that both legs float rather than one being fixed.
- Assuming that because both legs float there is no risk, when tenor and benchmark differences produce genuine and sometimes large cash flows.
- Treating the notional amount as money at stake, when in a single-currency basis swap only the net interest difference is ever exchanged.
Questions
People also ask.
Why would anyone swap one floating rate for another?
To match the benchmark on their funding to the benchmark on their assets, removing a mismatch that otherwise moves their margin unpredictably.
What is the basis spread?
The margin added to one leg to make the two floating streams economically equal at inception, quoted in basis points and driven by relative demand for each benchmark.
What is a cross-currency basis swap?
A version that exchanges floating payments in two different currencies, usually with principal exchanged at the start and repaid at the end.
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