Many corporate bonds (and some Indian NCDs) carry an embedded call option: the issuer may redeem the bond early, at a specified call price, on or after a specified call date, often a whole schedule of call dates, each with its own call price (frequently starting at a premium and stepping down toward par over time). From the bondholder's side, this is a bet they did not choose to make: if rates fall, the issuer calls the bond away and reinvests the proceeds at the new, lower rate, precisely when the bondholder least wants their income stream cut short.
Yield to call (YTC) is computed with the identical IRR machinery as YTM, substituting the call price and call date for the face value and maturity date: solve for the rate that discounts the coupons up to the call date, plus the call price at the call date, back to the current market price. A callable bond with n call dates in its schedule therefore has n distinct YTCs, plus its ordinary YTM to maturity, and yield to worst (YTW) is defined as the minimum across every one of those computed yields. The name is precise: an issuer holds the call option and will exercise it in whichever way is worst for the bondholder, so a disciplined analyst prices, and reports, the worst case, never the case they'd prefer.
Advertisement
Is the nearest call date always the worst case?
The single most common mistake here (drilled in the Common Mistakes section and in Worked Example 3's counter-example) is assuming YTW is automatically the yield to the nearest call date, on the intuition that an early call always hurts a premium bondholder most. That intuition is directionally common but not guaranteed, a call schedule with an unusually rich near-term call price (a "make-whole"-style premium) can make an early call the best outcome for the holder, with the true worst case sitting at a later, cheaper call date. There is no substitute for computing every date in the schedule; Worked Example 3 constructs exactly this counter-example with real, Python-verified numbers so you see it happen once, rather than merely being told it can.
What is yield to put for a puttable bond?
A puttable bond is the mirror image, the bondholder holds the option to redeem early at a specified put price, so a full yield-to-worst analysis for a puttable bond would also compute a yield to put (YTP) and, being an option the bondholder would only exercise in their own favor, would generally be looking for the maximum practical outcome rather than the minimum (the put floors the downside rather than capping the upside). This module does not build a worked YTP case, the full apparatus for valuing an embedded option properly (rather than the static, yield-based approximation YTC/YTW gives you) is a binomial-tree exercise, and that rigorous treatment, along with negative convexity and mortgage-backed prepayment behavior, is explicitly FI1.04's job. Treat YTC/YTW as the fast, static, "what if it happens on this exact date" approximation; FI1.04 replaces it with the real thing.