In plain language — For some bonds, final maturity is not the whole story. The issuer may be allowed to redeem early, the investor may be allowed to return the bond, or underlying borrowers may repay ahead of schedule.
A call contractually benefits the issuer: when conditions make it attractive, it may redeem the security on specified dates and at specified prices. A put gives that right to the bondholder. Prepayment changes the cash-flow sequence when underlying borrowers, such as mortgage borrowers, repay early.
These rights do not say that exercise will occur. They define possibilities and incentives that valuation must consider.
Calls: when upside can stop
If rates or the issuer's funding spread fall, refinancing may become attractive. A callable bond can then rise less than an otherwise similar option-free bond because redemption at a preset price becomes more likely. The investor receives principal but must reinvest under prevailing conditions.
The contract states call dates, prices, protection periods, notice and exceptions. A make-whole call, a fixed-price call and a regulatory call do not share one profile. The word “callable” alone is insufficient.
Yield to call calculates a yield assuming one particular exercise date. Yield to worst compares contractual scenarios under a stated convention. Neither automatically includes default, costs or a sale before the event.
Puts and prepayment
A put lets the holder demand repayment at stated dates and prices. It can limit part of adverse price sensitivity, but its value still depends on the issuer's ability to pay. A contractual right does not remove credit risk.
In mortgage-backed securities, borrowers can repay when they sell, refinance or for other reasons. When rates decline, prepayments may accelerate and return principal when reinvestment yields are lower. When rates rise, repayments may slow and extend cash flows: extension risk. Behaviour depends on more than rates; frictions, loan characteristics and economic conditions matter.
Measures change when cash flows change
Modified duration and convexity based on fixed cash flows can be inadequate. Effective duration reprices after curve shocks while allowing exercise or prepayment assumptions to change. OAS also tries to separate option value from spread through a rate model.
A callable bond can display reduced or negative convexity in some regions: as yields fall, the call constrains price gains. This behaviour is not constant and depends on price, curve, volatility and terms.
A professional workflow maps every exercise date, calculates scenario cash flows, checks models against observed prices and behaviour, and stresses rates, spreads and volatility. Sensitivities are versioned with assumptions.
Read the document before the number
Before using YTC or effective duration, identify who can exercise, valid dates and prices, notice periods, redeemable amounts, special events and payment priority. For asset-backed and mortgage-backed instruments, read structure, waterfall, servicing and prepayment assumptions.
Common error — Selecting the higher of YTM and YTC as if the issuer exercised for the investor's benefit. The option and incentive belong to the party named in the contract.
Questions this page answers
Who owns the option? Which dates and prices apply? Do modelled cash flows change with rates? Which scenario produces YTC or duration? Are prepayment and extension risks present? Does credit risk remain?
Sources
- FINRA — Callable Bonds: Understanding the Basics
- Investor.gov — Bonds or Fixed Income Products
- FINRA — Bonds