Variance Swaps and Basis Swaps Explained

Beyond the plain-vanilla interest rate swap, where one fixed rate is exchanged for one floating rate, trading desks use a range of more specialised swap structures to hedge or speculate on specific risks that a vanilla swap can't isolate. Two of the most widely used are variance swaps, which trade volatility itself as the underlying, and basis swaps, which exchange one floating rate for another rather than fixed for floating. Despite both being called "swaps," they solve very different problems.

Variance Swaps: Trading Volatility Directly

A variance swap is a derivative contract that lets the two counterparties exchange payments based on the difference between realised variance of an underlying asset (commonly an equity index, single stock, FX rate, or interest rate) over a set period, and a variance level agreed at inception (the strike). One party pays the other based on how much actual price variance exceeded or fell short of that strike, with no exchange of the underlying asset itself.

The appeal of a variance swap over a simple options-based volatility position is that it gives pure exposure to realised volatility without the path-dependency and delta-hedging headaches that come with replicating volatility exposure using options. A trading desk or hedge fund with a view that market turbulence is underpriced can buy variance (go long the swap) to profit if realised volatility comes in higher than the market implied at the time the trade was struck; an investor who believes volatility is overpriced can sell variance instead. Because payouts are driven by the square of returns, variance swaps have a distinctive payoff profile: losses for a variance seller can be large and accelerate sharply during a genuine volatility spike, which is exactly what happened to several funds that had sold variance heavily before major market dislocations.

Basis Swaps: Exchanging One Floating Rate for Another

A basis swap exchanges two floating-rate cash flows referencing different underlying rates, rather than exchanging fixed for floating as in a standard interest rate swap. Common examples include swapping one currency's interbank floating rate for another (a cross-currency basis swap), swapping a short-term reference rate for a longer-tenor version of the same curve (a tenor basis swap, e.g. three-month SOFR versus six-month SOFR), or swapping compounded overnight rates against a term rate benchmark.

Basis swaps exist because, in practice, different floating-rate benchmarks don't move in perfect lockstep — funding costs, credit risk, and liquidity differ between a three-month rate and a six-month rate, or between two currencies' money markets, even when both are nominally "risk-free" reference rates. Banks and corporates with assets and liabilities referencing different floating benchmarks use basis swaps to eliminate that mismatch risk precisely, rather than accepting basis risk as an unmanaged residual. Cross-currency basis swaps in particular became a closely watched market signal during periods of dollar funding stress, since a sharply negative basis reflects strong demand for dollar funding relative to supply through the swap market.

Why the Distinction Matters

Confusing these two products with a standard interest rate swap is a common beginner mistake, because all three share the word "swap" and involve periodic cash flow exchanges. The underlying risk being transferred is completely different in each case: an interest rate swap manages exposure to the general level of interest rates; a basis swap manages the spread between two related but distinct floating benchmarks; and a variance swap manages exposure to volatility itself, independent of the direction the underlying moves. A treasurer or risk manager who picks the wrong instrument for the risk they're actually trying to hedge can end up with a position that looks similar on paper but behaves completely differently when markets move.

Where These Instruments Are Used in Practice

Basis swaps are a core plumbing tool for banks managing multi-currency balance sheets and for corporates with debt or receivables in more than one reference rate or currency. Variance swaps are used mostly by hedge funds, proprietary trading desks, and sophisticated institutional investors running volatility-focused strategies, rather than appearing in typical corporate treasury hedging programmes. Both instruments, like a swaption, sit a step up in complexity from vanilla rate swaps and generally trade over-the-counter between sophisticated counterparties rather than on exchange.

FAQ

Is a variance swap the same as a volatility swap?
No, though they are related. A volatility swap pays out based on realised volatility (the square root of variance) directly, while a variance swap pays based on variance itself, which gives it a more convex payoff and makes it easier to replicate using a static portfolio of options.

Why would a bank use a basis swap instead of just accepting the mismatch?
Leaving a floating-rate mismatch unmanaged exposes the bank to basis risk that can widen unpredictably, particularly during periods of market stress, so hedging it with a basis swap converts an open risk into a known, managed cost.

Can a corporate treasury use these instruments, or are they only for trading desks?
Basis swaps are commonly used by corporate treasuries with genuine cross-currency or cross-tenor exposure; variance swaps are far less common outside specialist funds and trading desks given their complexity and payoff profile.

Understanding the full range of swap-based derivatives is covered across Learnsignal's CPD course content for finance professionals working in treasury, risk, and trading roles.