Swaption
Also known as: Swap option, Payer / receiver swaption
An option to enter a swap — the instrument through which the market prices interest-rate uncertainty itself.
- Asset class
- Rates derivatives
- Instrument type
- Option on a swap
- Traded
- OTC
- Typical users
- Mortgage hedgers, insurers, vol traders
BeginnerWhat is it, really?
A swaption is an option whose underlying is an interest rate swap. A payer swaption gives the right to enter a swap paying a fixed rate agreed today; it pays off if rates rise. A receiver swaption is the right to receive that fixed rate; it pays off if rates fall.
Names follow a "period into period" convention: a "1y into 10y" swaption expires in one year, on a swap that then runs ten more.
Who needs this? Anyone whose future depends on future rates: a company planning to borrow in a year buys a payer swaption as a rate ceiling that still lets it enjoy lower rates; insurers and pension funds buy receivers to protect against rate collapses that balloon their liabilities.
IntermediateHow it works in practice
Settlement and structure
- Physical: exercise into the actual swap; cash-settled: receive the swap's value at expiry (conventions differ by currency).
- Premium: paid upfront, quoted either in cash or — the trader's native unit — in implied volatility.
- The grid: quotes span expiry × swap tenor (1m into 2y … 10y into 30y), forming the volatility surface ("vol cube" with strike as the third axis).
Who drives the flows
- MBS hedgers: US mortgage books are short vol (homeowners' prepayment options); hedging them makes desks structural swaption buyers.
- Insurers/LDI: long-dated receivers hedge guarantees written to policyholders.
- Callable debt: every callable bond issued embeds a swaption; issuers/dealers recycle that vol into the market.
- Exotic desks: swaptions are calibration targets for anything Bermudan or path-dependent.
Straddles: trading pure uncertainty
Buying payer + receiver at the same strike (a straddle) profits from large moves either way — the standard vehicle for "rates will get wild" views around elections, inflation prints and policy pivots.
AdvancedPricing & valuation
Pricing in the annuity measure
The swap rate \(S_t\) is a martingale under the measure whose numéraire is the annuity \(A_t = \sum \delta_i P(t, T_i)\). A payer swaption struck at \(K\) is then a call on \(S_T\):
With normal (Bachelier) dynamics \(dS = \sigma_N\, dW\) — the market standard since rates went to zero and below:
Quotes are in normal vol (bp/year); lognormal (Black) quoting survives in some corners.
The smile and its models
Across strikes, implied vol forms a smile; the workhorse parameterisation is SABR (\(\beta\) controlling backbone, \(\rho\) skew, \(\nu\) smile curvature), fitted per expiry-tenor point. For products depending on the joint dynamics of many rates (Bermudans, callables), desks calibrate term-structure models — LMM (Libor/forward market models) or cheaper Hull–White/LGM — to the swaption grid.
Greeks with a twist
Vega splits by expiry-tenor bucket; delta is an annuity-weighted swap DV01; and cash-settled vs. physical conventions create measurable convexity differences (the famous CMS-linked corrections). Vol itself has term structure and its own risk premium — systematically selling rate vol has been a documented (and occasionally catastrophic) carry trade.