Foundation — What an interest rate really is, and what a fixed income security really is

Chapter 1 — Interest rate, interest rate instruments and the fixed income market

This is the longest chapter in the whole NISM Series-IV workbook and it carries 10% weightage. Everything that comes later — futures, options, strategies, trading, clearing — sits on top of this chapter. If bond pricing and duration are shaky here, Chapters 3, 4 and 5 will feel impossible. So take your time with this one.

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1. Debt is just "I owe you", written down

Forget formulas for a minute. Debt is the oldest arrangement in the world.

Suppose Ramesh borrows Rs 1,00,000 from his neighbour Suresh for 3 months and promises to return Rs 1,01,500. In workbook language:

• Ramesh is the borrower, Suresh is the lender
• Rs 1,00,000 is the principal (call it X)
• Rs 1,500 is the extra (call it Δ)
• The rate is worked out as Δ = X × R% × 3/12, so R = 6% per annum

Now there are two ways to record this.

Way one — a Loan. They sign an agreement. Suresh cannot easily pass this agreement to a third person. A loan is generally non-tradable. Suresh is stuck with Ramesh's risk until the money comes back.

Way two — a Note. Ramesh writes out: "I will repay Rs 1,00,000 with interest at 6% p.a. after 3 months, to whoever holds this note." Now Suresh can sell that note to Mahesh next month if he needs cash. That note is a debt instrument / debt security — a tradable promise.

That single difference — tradability — is the whole reason a debt market exists. In market vocabulary the same people get new names: Ramesh is the Issuer, Suresh is the Investor, and R is the yield on the date of the deal.

Assets borrowed need not be money alone — vehicles, property, consumer goods all carry an implicit interest cost. And rates are almost always quoted per annum, which the market calls the nominal annual interest rate.

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2. "Interest rate is 6%" tells you nothing

The workbook makes a sharp point here and the exam loves it: interest rate is subjective. Look at this list of real-life Indian quotes:

Change the tenor, the rate changes. Change the amount, the rate changes. Change the borrower's credit quality, the rate changes. Change the security backing it, the rate changes.

Simple rule the exam wants: the lower the perceived risk of the borrower, the lower the rate charged. The higher the risk, the higher the rate.

2.1 Macro factors that move rates in the whole economy

1. Demand for money. Economy doing well → businesses want funds for projects → demand for funds rises → cost of money (interest rate) rises. In recession, demand collapses and rates sag.
2. Supply of money. Controlled mainly by the central bank. When inflation kicks in, RBI tightens money supply and raises the policy rate to make funds costlier.
3. Fiscal deficit and government borrowing. When the government must borrow heavily, traders demand a higher rate to absorb that supply, and corporates find funds constrained. This is the classic "crowding out".
4. Inflation. If prices rise, the real value of a saver's money falls. Savers demand compensation, so nominal rates must rise. When inflation cools, nominal rates come down.
5. Global interest rates and forex rates. Global investors arbitrage between countries. If rates rise abroad, money leaves India — so domestic rates have to move up to stay attractive.
6. Central bank actions. A rise in the Repo rate feeds into money market rates, which in turn feeds into bond market yields.

2.2 Micro factors specific to one bond

1. Maturity / tenor — generally positively correlated with rate. Longer tenor, higher rate.
2. Credit risk — higher perceived default risk, higher rate.
3. Seniority — where you stand in the repayment queue if the issuer goes bankrupt. Lower seniority, higher rate.
4. Security — secured bonds are backed by specific assets; unsecured bonds pay more to compensate.
5. Liquidity — how easily the bond can be bought or sold without moving its price. Investors pay a premium for easily traded bonds (i.e. accept a lower yield).
6. Investor sentiment — when mood turns negative, money rushes to safe assets like government securities.

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3. Three rates that sound the same but are not

3.1 Effective rate (compounding effect)

A bond pays 6% annually but compounds semi-annually. Invest Rs 1,000:

• After 6 months: Rs 1,000 × 3% = Rs 30
• Reinvest that Rs 30 in the same bond. After the next 6 months: Rs 1,030 × 3% = Rs 30.90
• Total for the year: Rs 60.90 on Rs 1,000 = 6.09%

So the nominal rate is 6% but the effective rate is 6.09%.

$$\text{Effective rate} = \left(1 + \frac{\text{annual rate}}{n}\right)^n - 1$$

where n = number of compounding periods per year. Here (1 + 6%/2)² − 1 = 6.09%.

3.2 Nominal versus real interest rate

The nominal rate is the stated rate — the coupon the issuer pays. But inflation quietly eats purchasing power. Adjust the nominal rate for inflation and you get the real interest rate.

Exact relation: (1 + r) × (1 + i) = (1 + R), where r = real, i = inflation, R = nominal.

For small numbers this simplifies beautifully to:

• Nominal 9%, inflation 6% → real rate ≈ 3%. You are actually getting richer.
• Nominal 7%, inflation 9% → real rate ≈ −2%. You are getting poorer while feeling richer.

Many Indian savers lived through exactly this in 2020–2022: bank FDs at 5.5% while CPI inflation ran near 7%. The passbook balance grew; the shopping power shrank. That negative real rate is precisely why household money began shifting into equity, gold and debt funds in those years.

3.3 Quick recap box

• Interest rate is the amount charged on top of principal for use of an asset
• Expressed as a percentage of principal
• Noted on an annual basis
• Interest rate is subjective
• Decided by many factors
• Interest rate risk = uncertainty in the movement of interest rates
• Movement both ways hurts somebody — it is never one-sided

That last point matters more than students expect. A borrower planning to borrow next year fears rates going up. A lender planning to lend next year fears rates going down. Banks and NBFCs have exposure on both the asset and liability side, at different tenors — so they can be hurt by either direction. This two-sided nature is the entire commercial reason interest rate derivatives exist.

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4. What makes a security "fixed income"

Fixed income securities are debt instruments that pay a fixed amount of interest as coupon at periodic intervals, and return the principal at maturity. Bonds and debentures are the most common form.

They are called "fixed income" because of these fixed features:

• Their life is fixed — they get redeemed on a specified future date, because every borrow-lend deal is for a fixed period. The workbook's charming exception: a Dutch perpetual bond issued in 1648 that still pays. In India, some banks and corporates issue perpetual bonds — but these are not strictly perpetual, because the issuer holds a call option.
• In most cases the cash flows are fixed too — timing and size known in advance. In floating-rate bonds the timing is known but the size is not, because the amount is linked to a prevailing rate.

4.1 The key components — learn these cold

A worked-out specimen: Security with FV Rs 1,000 issued 01-Apr-2021 for 10 years at Rs 1,000, coupon 7% p.a. paid every 6 months.

• Issue price = Rs 1,000 · Face value = Rs 1,000 · Coupon = 7%
• Frequency = half-yearly · Interest payment dates = 1 April and 1 October
• Maturity date = 01-Apr-2031 · Put = N.A. · Call = N.A. · Redemption value = Rs 1,000

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5. The family tree of bonds

A bond is a security issued by a legal entity to raise funds, promising to return the principal and pay the promised coupon. It is like a loan — except it is tradable.

That difference has a consequence students often miss: the value of a loan does not change, but the value of a bond changes continuously with future interest rate expectations and with the borrower's credit worthiness. A lender with a loan carries permanent risk till repayment; a bondholder can transfer that risk to another risk-taker through the pricing mechanism.

Bonds are classified by: issuer, maturity, coupon, currency, embedded options, security, priority of claims, purpose of issue, underlying, and taxation.

5.1 By type of issuer

Government / Sovereign / Gilt-edged bonds. Issued by government, typically in domestic currency. Considered risk-free in local currency because a sovereign can print currency to repay. But the European debt crisis (2008–2012) showed governments can default in emergencies. Low risk → lower rates than other issuers. In India, G-secs are the largest segment of the fixed income market, and include:

• Central Government dated securities
• State Development Loans (SDLs) issued by State Governments and Union Territories
• Special securities issued for subsidies — oil, fertiliser, bank recapitalisation

Municipal bonds ("muni bonds"). Issued by local authorities for infrastructure, libraries, parks. Categorised by the source of interest and principal payments. In India very few municipal bodies have issued so far, but the market is picking up — Pune, Ahmedabad, Indore, Lucknow and Vadodara have all done municipal bond issues in recent years, and Indore's 2023 green municipal bond was even opened to retail investors. SEBI has a separate regulation for issuance and listing of municipal bonds.

Corporate bonds / NCDs. Issued by companies to raise capital. Performance depends on the company's future revenue and profit. Debt is cheaper than equity and does not dilute ownership. Physical assets may be pledged as collateral. Riskier than G-secs → investors demand higher rates. For short-term needs, corporates issue Commercial Papers (CPs). Issued through public issuance or private placement. Creditworthiness is assessed periodically by one or more credit rating agencies. Highest quality = "AAA"; high-risk = "junk" or "high-yield". The gap between corporate bond yields and government bond yields is the credit spread.

Securitised debt. Securitisation converts illiquid loan assets of a lender (say a bank's pool of car loans) into a liquid pool of tradable assets. Done by creating a Special Purpose Vehicle (SPV) and structuring the loan pool into tradable bonds. Ownership of the loans and receivables is transferred to the SPV.

5.2 By maturity

⚠️ Exam trap: the workbook explicitly says there is no specific guideline for what counts as short, medium or long. And note that mutual funds classify debt funds by "duration", not by maturity tenor.

Staggered maturities. Some issues are packaged as a series of bonds maturing at different times. Every few years a portion matures and is paid off. This lets the issuer retire debt in an orderly way instead of facing one giant cash need. Serial payments follow this staggered schedule.

Perpetual bonds (Consol bonds). No maturity date; keep paying coupons through the life of the company. Banks are the primary issuers, using them to meet Tier-I capital requirements under Basel III.

5.3 By coupon

• Plain vanilla bond — simplest form: fixed coupon, defined maturity, issued and redeemed at face value. Also called straight bond or bullet bond.
• Zero coupon bond (ZCB) — pays no interest; issued at a discount, redeemed at face value. The difference is the return. Single cash flow at maturity. Indian examples: Treasury Bills, Cash Management Bills, and STRIPS (created by stripping off coupons from the principal and trading them separately). ZCBs are highly sensitive to interest rate changes because there are no intervening cash flows — which is exactly why pension funds and insurance companies use them to offset the interest rate risk of long-term liabilities.
• Floating rate bonds (FRBs) — no pre-fixed coupon; linked to a benchmark (in India often the 182-day T-bill rate). Coupon resets on each coupon payment date. Rates rise → coupon rises. FRBs trade very close to face value because of regular resets, so they are largely immune to interest rate risk and are considered conservative.
• Caps and floors — a cap limits the issuer's interest obligation if rates rise; a floor protects the investor from rates falling too far. A bond with both a cap and a floor is called a "Collar".
• Inverse floater — coupon moves opposite to the benchmark. Benchmark up → coupon down. In India usually structured as a negative spread over a fixed rate, a few percentage points over the MIBOR benchmark. Mostly used by NBFCs to raise funds, with mutual funds as primary investors.
• Inflation indexed bonds — a type of FRB protecting investors from rising prices, indexed to WPI or CPI. Either the face value alone, or both face value and coupons, may be indexed.
• Step up bonds — lower coupon in early years, higher near maturity. Preferred by issuers like start-ups expecting cash flows to balloon later. Investors take higher risk, so demand a higher rate. Generally risky.
• Step down bonds — exact opposite: high coupon early, dropping towards maturity. Issued where revenues are expected to decline in a phased way — e.g. leasing, where machinery wears out. Both step up and step down help with cash flow planning.
• Deferred coupon bonds — a mix of coupon bond and ZCB. No interest in the initial years, then very high interest a few years before maturity. Preferred by corporates with long gestation periods.
• Deep discount bonds — a ZCB issued at a high discount to face value. Typically a discount of 20% or more with relatively long maturity. Issued by infrastructure companies with very long gestation. Carry high risk.

5.4 By embedded options

An embedded-option bond carries callability by the issuer and/or puttability by the investor. Optionality changes the price because the risk profile changes. Such bonds are valued using option premia.

• Straight bond — no option; regular coupon, principal at maturity. Most basic form.
• Bond with a call option — the issuer may call the bond back before maturity at a pre-fixed call date. The issuer will do this when market rates have fallen below the bond's coupon (refinancing gets cheaper). Callable bonds usually require a premium at redemption when called.
• Bond with a put option — the investor may seek redemption before maturity at a pre-fixed put date. The investor will do this when market rates have risen above the bond's coupon. Such bonds generally require a discount at the time of early redemption.
• Bond with both call and put — either side can trigger early redemption.

Memory hook: Call is the issuer's escape when rates fall. Put is the investor's escape when rates rise. Each side runs when the market moves against them.

5.5 By security

• Secured debt — backed by specific assets, with collateral ranking. Paid first out of the assigned assets. Higher recovery rate than unsecured bonds if the company defaults.
• Unsecured debt — no specific collateral allocated. Companies issue on the strength of their name and reputation.
• Credit enhanced bonds — the issuer improves the credit worthiness of the offering through additional collateral, insurance, or a third-party guarantee. This lowers the borrowing cost, improves the rating grade and reduces investor risk.

5.6 By seniority (priority of claims)

• Senior debt — higher priority in the repayment queue on bankruptcy or liquidation. Paid before subordinated debt holders and shareholders. Lower risk → lower interest rate.
• Subordinated debt — higher coupon but riskier; paid just before equity holders at liquidation. In India, banks issue subordinated bonds to shore up Tier II capital under capital adequacy rules.

5.7 Other instruments you should recognise by name

• Annuities — financial products paying monthly amounts over a period. Treated as a fixed income asset class, but cannot be traded in the secondary market like a bond. You invest lump-sum or over time and receive regular payments. Most consumer loans and housing loans are structured as annuities.
• AT1 (Additional Tier-1) bonds — under Basel III, bank regulatory capital splits into Tier 1 and Tier 2; Tier 1 splits into CET1 (equity capital) and AT-1. Perpetual bonds satisfying RBI conditions are classified as AT-1. Unsecured, perpetual, non-convertible. Indian investors learned about these the hard way in the YES Bank rescue of March 2020, when AT-1 bonds worth about Rs 8,400 crore were written down to zero while equity holders retained something — a reminder that AT-1 is capital, not a safe deposit.
• AT2 (Tier 2) bonds — debt instruments forming Tier 2 capital, mainly for banks. No ownership or voting rights, only interest. Minimum 5 years at issue. Unsecured and subordinated to depositors, unsecured creditors and senior bonds. No put option — only a call option, exercisable after a minimum of 5 years and after RBI approval.
• Convertible bonds — convert into equity shares at a specified time at a pre-fixed conversion price. The bondholder has the right to convert and the issuing company cannot refuse, because it was agreed at issuance.
• REITs — trusts registered with SEBI investing in commercial real estate. Raise funds through an initial offer and later through follow-on offers, rights issues and institutional placements.
• InvITs — trusts registered with SEBI investing in the infrastructure sector. Raise funds from the public through an initial offer of units; the cash flow generated is distributed to investors.
• Green bonds — fixed income instruments earmarked to raise money for climate and environmental projects. Typically asset-linked and backed by the issuer's balance sheet, so they usually carry the same credit rating as the issuer's other debt.
• ESG Debt Securities — SEBI, by circular dated June 05, 2025, provided a framework for Environment, Social and Governance debt securities other than green debt securities. The definition covers green debt securities, social bonds, sustainability bonds, sustainability-linked bonds, or any other bonds issued in accordance with international frameworks adapted to Indian requirements as specified by SEBI.
• Tax-free bonds — issued by a government enterprise for a particular purpose; interest is fully exempt under Section 10 of the Income Tax Act, 1961.
• Tax saving bonds — offer a tax benefit and come with a minimum lock-in. Careful: the interest earned on these is taxable.
• Asset linked bonds — linked to some asset, giving better credit enhancement; repayment capacity depends on the underlying asset's performance.
• Masala bonds — rupee-denominated bonds issued outside India by Indian entities, helping raise money in local currency from foreign investors.

⚠️ Classic exam trap: tax-free bonds → interest exempt. Tax-saving bonds → the investment gets a benefit but the interest is taxable. Students mix these two up every single time.

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6. Equity versus debt

6.1 Advantages of debt compared to equity

• Debt is a long term source of capital
• Borrowing does not reduce control of the company for the owner; lenders rank above equity holders in bankruptcy
• The lender gets the promised rate and principal — indifferent to the company's profit
• Future obligations are mostly known, so cash flow and repayment planning is possible
• Interest is tax-deductible as an expense, which reduces the weighted average cost of capital. The higher the company's marginal tax rate, the bigger this saving
• Raising large debt through private placement is less complicated — sold to qualified institutional buyers, avoiding the complex regulations of a public equity issue
• No periodic mailings to large numbers of investors, no periodic shareholder meetings, no shareholder vote before certain actions
• Lenders tend to be more committed than equity holders
• In the long run debt is cheaper than equity, because the eventual return equity holders demand exceeds the interest on debt

6.2 Disadvantages of debt compared to equity

• Some debt instruments restrict the company's core activities; exclusivity clauses can hurt
• Unlike equity, debt must be repaid — a liquidity outflow
• Repayment causes cash flow risk; the company may fail to refinance if markets turn bad
• Debt is leverage — high leverage can jeopardise growth plans and raise default risk. Historically many good companies went bankrupt under the burden of huge debt
• Obligations are fixed at issuance and must be repaid irrespective of market conditions
• Poorly planned repayment can disrupt working capital, production plans and operations
• The larger the debt-equity ratio, the riskier the company looks — so there is a limit to how much debt a business can carry
• Secured debentures may require a lien on assets or a sinking fund out of operating cash flows — burdensome in times of market stress

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7. The risk-free rate — and why "fixed income" ≠ "fixed return"

Here is one of the most quoted lines in the workbook, and a favourite exam sentence:

Take a 7-year corporate bond paying 9% p.a. Why is 9% not guaranteed?

1. Credit risk. The company may fail to pay interest or principal on schedule.
2. Price risk (interest rate risk / market risk). The 9% is guaranteed only if you hold to maturity. Want your money at the end of 5 years? You cannot demand prepayment from the issuer — you must sell in the secondary market, at a price that may be higher or lower than what you paid. That capital gain or loss is not known in advance.
3. Reinvestment risk. If your horizon is 7 years, ideally there should be no interim payments. But there are — the annual coupons. Each must be reinvested at unknown future rates: year 1's coupon for 6 more years, year 2's for 5 more years, and so on. Since those rates are unknown today, this is reinvestment risk.

Plus liquidity risk (a thin market with few buyers and sellers, causing price volatility and hurting your realised return on sale), call risk and inflation risk.

7.1 The most important table in the chapter

Price risk and reinvestment risk always work in opposite directions:

And the timing differs: the price change is instant after a rate move, whereas the effect on reinvestment income is slow, spread over the remaining life.

7.2 So where does "risk-free" come from?

If the borrower is a sovereign government and the borrowing is in its home currency, there is no possibility of default — the sovereign can always print money. No credit risk. The rate applicable to such transactions is the "risk-free" rate, the risk in question being credit risk.

Everyone else may default, so their rate must be higher. The gap is the credit spread. In practice all borrowers are grouped by credit rating and the rate is quoted as a spread over the risk-free rate:

• Risk-free rate 8.25%, AAA credit spread 0.10% → AAA borrower pays 8.35%
• Risk-free rate 8.25%, AA credit spread 0.25% → AA borrower pays 8.50%

7.3 When does each risk actually disappear?

• Market (price) risk disappears if the investor holds till maturity, when the issuer redeems at face value
• Reinvestment risk disappears if the instrument is a zero coupon instrument — nothing to reinvest in the interim
• Credit risk disappears if the issuer is a sovereign borrowing in its home currency

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8. Why the debt market matters to the country

Financial markets group into three super asset classes: underlying, derivative and structured finance. Besides these there are collective investment schemes (mutual funds), physical assets (real estate, commodities, art, antiques, wine) and alternative assets (ETFs, managed futures, hedge funds, private equity).

The underlying super asset class has four fundamental asset classes — money, bond, equity and forex. They are called fundamental because they are independent, and traditional because savers have always parked money in them.

• Money market + bond market together = fixed income securities (FIS) market
• Debt market + equity market together = capital market (they are the two parts of a corporate body's capital)
• A capital market deals in long-term (over a year) debt or equity-backed securities; a money market deals in short-term fixed income securities
• The derivative class is not independent — it is derived from the underlying. There can be no derivative without an underlying.

Economic roles:

Forex traditionally serves production-consumption in international trade, but can also be used for financing when one borrows or lends foreign currency instead of home currency.

8.1 Importance of a developed debt market

• The Government is usually the largest issuer; a developed market helps it raise debt at reasonable cost
• A liquid market lowers borrowing cost for everyone and gives greater pricing efficiency
• A corporate bond market lets economic entities raise funds cheaper than bank loans
• It brings together many buyers and sellers, so debt is priced efficiently
• It reduces the degree of banking support needed by the economy, as risk gets distributed among many investors
• It helps the banking system with better Asset-Liability Management
• It channels collective investment schemes into the market and brings retail investors in directly
• It helps long-term investors like pension funds and insurance companies match and immunise their liabilities

Primary market lets governments and corporates sell securities directly to investors — governments typically through auctions, corporates typically through private placement. The secondary market provides an exit route and generates information through price discovery — credit risk appetite, spreads, default probability.

But issuance is a multi-level process: underwriting, credit rating, listing, coordinating with issue managers, liquidity, banking support. A well-functioning debt market needs a sustainable legal framework with clear bankruptcy codes. The regulatory cost can be prohibitive for smaller borrowers — which is why small and medium firms usually prefer bank borrowing over debt issuance.