Yield to Maturity (YTM)

Definition

Yield to Maturity (YTM) is the single discount rate that equates the present value of all future cash flows from a bond — periodic coupon payments plus the face-value repayment at maturity — to the bond's current market price (plus accrued interest). Mathematically it is the Internal Rate of Return (IRR) of the bond's cash-flow stream. The formula for a bond with n semi-annual periods, coupon C, face value F, and price P is:

P = Σ [C / (1 + y/2)^t] + F / (1 + y/2)^n

where y is the annual YTM and the sum runs from t = 1 to n. YTM is the fixed-income analogue of an equity's expected return — it tells investors how much they earn annually if every assumption holds. On NSE and BSE bond platforms, YTM is the primary quoted metric for secondary-market G-Secs and corporate bonds.

How it is computed

YTM has no closed-form algebraic solution; it is solved iteratively (Newton-Raphson or bisection). The inputs are: (a) current dirty price (clean price + accrued interest), (b) coupon rate and frequency, (c) face value, and (d) exact days to each cash-flow date. Indian G-Secs follow the Actual/Actual (ISDA) day-count convention; most corporate bonds use Actual/365. RBI's Negotiated Dealing System — Order Matching (NDS-OM) computes and displays YTM in real time on every trade. SEBI's ILDS Regulations 2008 require listed corporate bonds to disclose YTM in offer documents and on exchange platforms. A bond trading below par (market price < face value) will show a YTM higher than its coupon rate; above par, YTM < coupon rate; at par, YTM = coupon rate.

Why it matters for investors

YTM enables apples-to-apples comparison across bonds with different coupons, maturities, and prices. A 10-year G-Sec at 7.25% YTM and a 5-year AAA corporate bond at 7.90% YTM are immediately comparable after adjusting for credit spread and duration. YTM is also the basis for: (1) calculating current yield (annual coupon ÷ price — a cruder metric that ignores capital gain/loss to maturity); (2) deriving the G-Sec yield curve used by RBI for monetary policy signalling; and (3) pricing debt mutual fund NAVs daily via mark-to-market under SEBI's mutual fund regulations. However, YTM is a promised return, not a realised return — it assumes zero default and perfect reinvestment of every coupon at the same YTM, which rarely holds in practice.

Worked example

Consider the GOI 7.26% 2033 G-Sec (ISIN IN0020190042). On a hypothetical settlement date, the bond trades at a clean price of ₹99.60 with 180 days of accrued interest on a ₹100 face value. The dirty price = ₹99.60 + (7.26% × 180/365 × 100) = ₹99.60 + ₹3.578 = ₹103.178. Semi-annual coupon = ₹3.63 (half of 7.26%). With 9.5 years to maturity (19 semi-annual periods remain), solving iteratively:

₹103.178 = Σ [3.63 / (1 + y/2)^t] + 100 / (1 + y/2)^19

The YTM solves to approximately 6.98% per annum — below the coupon rate because the bond is trading above par. A NABARD AAA bond of similar tenor might quote YTM of 7.45%, implying a credit spread of ~47 bps over the G-Sec benchmark.

Caveats

Reinvestment assumption: YTM assumes coupons are reinvested at the same YTM — unrealistic if rates fall significantly after purchase. Realised yield (also called total return) will differ. Price sensitivity: YTM is inversely related to price; a 100 bps rise in yields on a 10-year bond causes roughly an 8–9% fall in price (quantified by modified duration). Credit events: If the issuer defaults, actual cash flows fall short of the YTM assumption. Tax drag: Post-Finance Act 2023, gains from debt MFs and bonds are taxed at slab rates (§50AA) for units acquired after 1 April 2023, reducing after-tax yield vs. the headline YTM figure. Always compare after-tax YTMs for personal finance decisions.

See also

• Modified Duration
• Credit Spread
• Yield Curve
• Debt Funds in India — Complete Guide
• Tax on Investments in India

Primary source

• RBI NDS-OM trading platform: rbi.org.in/scripts/nds.aspx
• SEBI ILDS Regulations 2008: sebi.gov.in — NCS Regulations 2021
• Finance Act 2023, Section 50AA (debt fund taxation)

MintByte is registered with AMFI (ARN-314872) and APMI (APRN-01658). This glossary entry is for educational purposes only and does not constitute investment advice or a recommendation to buy or sell any security.