A debt security is a loan you make to a government or a corporation, packaged as a financial instrument you can hold or trade. When you buy a bond, Treasury note, or similar product, the borrower commits to paying you interest on a fixed schedule and returning your principal on a specific date. That commitment is a legally enforceable contract, and if the borrower goes bankrupt, you stand ahead of stockholders in the recovery line.
That is the whole idea in one sentence. The details, though, are where investors either earn a predictable return or get an unpleasant surprise. Below is what actually matters before you buy one.
The Four Numbers That Define Every Bond
Every debt security revolves around four elements that determine what you earn and when you get paid.
Face value, also called par value, is the amount the borrower promises to repay when the security matures. Most bonds are issued in $1,000 increments, and that face value stays constant no matter what happens to the bond’s market price in the meantime.1Municipal Securities Rulemaking Board. Municipal Bond Basics
The coupon rate is the annual interest rate the borrower pays, expressed as a percentage of face value. A bond with a $1,000 face value and a 5% coupon pays $50 per year, usually split into two $25 payments every six months. That rate is locked in at issuance and doesn’t change.
The maturity date is the calendar date the borrower must return the full face value. Maturities range from a few days on short-term instruments to 30 years on long-term government bonds. Once the principal is repaid, the security is extinguished and interest stops.
Yield is where things get interesting. The coupon tells you what the borrower pays relative to face value, but yield tells you what you actually earn based on what you paid for the bond. Buy a 5% coupon bond for less than $1,000 and your yield-to-maturity runs higher than 5%, because you’re collecting the same $50 on a smaller investment. Buy it above $1,000 and your yield drops below 5%. This distinction matters because bonds trade on the open market at prices that shift constantly.
Types of Debt Securities
Debt instruments break into categories based on who’s borrowing your money and for how long. Each type carries different risks and different tax consequences, so the choice isn’t just about interest rates.
U.S. Treasury Securities
Treasuries are debt issued by the federal government through the Department of the Treasury. They’re considered among the safest investments in the world because they’re backed by the full faith and credit of the U.S. government. They come in three main flavors based on maturity:
- Treasury Bills (T-Bills) mature in one year or less. These don’t pay periodic interest. You buy them at a discount and receive the full face value at maturity, pocketing the difference.
- Treasury Notes (T-Notes) mature in two to ten years and pay interest every six months.
- Treasury Bonds (T-Bonds) are offered in 20-year and 30-year terms, with semi-annual interest payments.2TreasuryDirect. Treasury Bonds
The Treasury also issues Treasury Inflation-Protected Securities (TIPS). The principal on a TIPS adjusts based on changes in the Consumer Price Index, and interest is calculated on that adjusted principal every six months. If inflation runs at 3% and your TIPS pays a 1.5% coupon, your real return stays positive because the principal itself grows with prices.3TreasuryDirect. TIPS/CPI Data
Treasury interest is subject to federal income tax but exempt from all state and local income taxes, which can meaningfully boost your after-tax return if you live in a high-tax state.4Internal Revenue Service. Topic No. 403, Interest Received
Corporate Bonds
Corporations issue bonds to fund operations, expansions, or acquisitions. The quality of these bonds varies enormously depending on the company’s financial health. Credit rating agencies like S&P Global and Moody’s assign letter grades to help investors gauge the risk.
Bonds rated BBB- or higher by S&P (Baa3 by Moody’s) are classified as investment grade, meaning the issuer has a reasonably strong capacity to meet its obligations.5S&P Global. Understanding Credit Ratings Anything below that threshold is called high-yield or, less charitably, “junk.” High-yield bonds compensate for the added default risk by paying higher interest rates.
Interest on corporate bonds is taxable as ordinary income at both the federal and state level.4Internal Revenue Service. Topic No. 403, Interest Received
Municipal Bonds
State and local governments issue municipal bonds to fund public projects like roads, schools, and water systems. The headline appeal for investors is the tax treatment: interest on most municipal bonds is excluded from federal gross income.6Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds If you live in the state that issued the bond, the interest is often exempt from state and local taxes as well.1Municipal Securities Rulemaking Board. Municipal Bond Basics
That tax advantage means municipal issuers can offer lower coupons than comparable corporate bonds and still deliver competitive after-tax returns. To compare a muni against a taxable bond, divide the muni yield by one minus your marginal tax rate. A 3.5% muni yield is worth the equivalent of about 5.4% to someone in the 35% federal bracket. Credit quality varies by issuer, so treat munis with the same analytical rigor you’d apply to a corporate bond.
Money Market Instruments
These are short-term debt securities maturing in one year or less, designed for liquidity rather than long-term income. Commercial paper is short-term, unsecured debt issued by large corporations, typically to cover payroll or inventory needs. It’s usually sold at a discount to face value rather than paying periodic interest. You buy it for, say, $990 and receive $1,000 at maturity a few months later. Because commercial paper is unsecured, only financially strong companies can issue it at attractive rates.
Certificates of deposit (CDs) are time deposits issued by banks. They pay a fixed rate for a set term, and early withdrawal usually triggers a penalty. CDs up to $250,000 per depositor per bank are insured by the FDIC, which makes them one of the lowest-risk options in the debt universe.
How Debt Securities Trade and How You Buy Them
Unlike stocks, most bonds don’t trade on a centralized exchange. The secondary bond market operates primarily over-the-counter, meaning buyers and sellers negotiate through broker-dealers rather than matching orders on an exchange floor. Hundreds of thousands of individual securities are outstanding, and many trade infrequently. A dealer often buys from one investor, holds the bond temporarily, and sells to another at a markup.
The practical consequence is that pricing is less transparent than in the stock market. You won’t always see a live bid-ask quote, and the spread between what a dealer pays and what they charge can eat into your return on smaller trades.
TreasuryDirect
For U.S. Treasuries, the simplest route is TreasuryDirect, the government’s online portal. You can purchase T-Bills, T-Notes, T-Bonds, and TIPS directly from the Treasury at auction with no commission or markup. The minimum purchase is just $100.7TreasuryDirect. Buying a Treasury Marketable Security Securities are held electronically in your account, and the system runs around the clock.8TreasuryDirect. Investing Directly With the U.S. Treasury (FS Publication 009)
The tradeoff is flexibility. TreasuryDirect doesn’t support selling before maturity, so if you need to exit early, you’d have to transfer the security to a brokerage account first. For Treasuries you plan to hold to maturity, it’s hard to beat on cost.
Brokerage Accounts
A standard brokerage account lets you buy Treasuries, corporate bonds, and municipal bonds on the secondary market. Most brokerages require a minimum purchase of two bonds (roughly $2,000 in face value), though this varies by firm and bond. You’ll pay a commission or markup, but you gain the ability to sell whenever you want.
Bond Funds Versus Individual Bonds
Many retail investors access debt securities through bond mutual funds or ETFs rather than buying individual bonds. A bond fund pools money from many investors and holds dozens or hundreds of bonds, giving you instant diversification for a relatively small investment. Fund shares pay income monthly rather than semi-annually, and the manager handles reinvestment and credit monitoring.
The key difference is that a bond fund has no maturity date. Individual bonds return your principal on a known date; a fund’s share price fluctuates indefinitely. If interest rates rise, a bond fund’s price drops and stays down until the underlying portfolio turns over. You can’t simply wait until maturity to get your money back. For investors who want predictable cash flow and a guaranteed return of principal at a set date, individual bonds have an edge. For investors who want diversification and professional management without needing six figures to build a proper portfolio, funds are the practical choice.
The Risks That Actually Move Bond Prices
Debt securities are generally less volatile than stocks, but less volatile doesn’t mean risk-free.
Interest Rate Risk
Bond prices and interest rates move in opposite directions. When rates rise, newly issued bonds offer better coupons, making your older, lower-coupon bond less attractive. Its market price has to fall until its yield matches what new bonds are paying. This dynamic hits hardest on long-maturity bonds because there are more future payments being discounted at the new, higher rate. Hold to maturity and you’ll still get your full face value back. Sell early in a rising-rate environment and you’ll take a loss.
Credit Risk
Credit risk is the possibility that the borrower simply can’t pay. It ranges from negligible for U.S. Treasuries to very real for high-yield corporate bonds. Rating agencies exist to quantify this risk, but ratings can lag reality. A downgrade doesn’t just signal trouble ahead; it immediately hammers the bond’s price because investors demand a wider spread to hold riskier debt.
The gap between what a corporate bond yields and what a Treasury of similar maturity yields is called the credit spread. That spread is essentially the market’s real-time pricing of default risk. When economic conditions deteriorate, spreads widen across the board, even for investment-grade issuers.9Federal Reserve Bank of St. Louis. ICE BofA US Corporate Index Option-Adjusted Spread
Inflation Risk
A fixed coupon payment buys less each year if prices are rising faster than the interest you’re earning. A bond paying 4% sounds fine until inflation hits 5%. Your principal repayment at maturity also loses purchasing power over time. Long-term bonds are most vulnerable because inflation compounds over decades. TIPS address this by tying the bond’s principal to the Consumer Price Index, but they carry lower coupons and can lose principal value during deflationary periods.3TreasuryDirect. TIPS/CPI Data
Call and Reinvestment Risk
Some bonds give the issuer the right to repay the principal early, usually after a set protection period. Municipal bonds frequently include a call option exercisable ten years after issuance. Issuers call bonds when interest rates drop because they can refinance at a lower cost.
The problem for you is twofold. You lose a bond that was paying above-market interest, and you get your principal back in exactly the environment where reinvesting it at a comparable rate is difficult. Reinvestment risk also applies in a milder form whenever you receive coupon payments during falling-rate periods and can’t put that cash to work at the same yield.
Taxes on Debt Securities
Tax rules vary significantly depending on what you own and how you dispose of it. Getting this wrong can cost you real money, especially with municipal bonds where the tax advantage is the whole point.
Interest on corporate bonds and CDs is taxed as ordinary income at the federal and state level. Treasury interest is taxable federally but exempt from state and local income taxes.4Internal Revenue Service. Topic No. 403, Interest Received Municipal bond interest is generally excluded from federal gross income, with exceptions for certain private activity bonds and arbitrage bonds.6Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds
Zero-coupon bonds and other instruments sold below face value at issuance create what the IRS calls original issue discount (OID). OID is treated as a form of interest, and you must include it in income as it accrues each year, even though you don’t receive any cash until maturity. This catches many investors off guard. You owe tax annually on income you haven’t actually received yet.10Internal Revenue Service. Publication 1212 – Guide to Original Issue Discount (OID)
Selling before maturity is different from holding to maturity. Any gain on a bond purchased at a market discount is treated as ordinary income to the extent of the accrued discount, not as a capital gain.11Office of the Law Revision Counsel. 26 USC Subtitle A, Chapter 1, Subchapter P – Capital Gains and Losses Gains above the accrued discount receive capital gains treatment, with the rate depending on how long you held the bond.
What Happens If the Issuer Defaults
Default is the scenario every bond investor dreads, but the process is more structured than most people realize. Federal law provides a framework designed to protect creditors when things go wrong.
Any publicly offered corporate bond issue must appoint an independent trustee under the Trust Indenture Act. That trustee, usually a large bank, acts as a watchdog on behalf of all bondholders. Once default occurs, the trustee must exercise its powers with the same care and skill a prudent person would use in managing their own affairs.12Office of the Law Revision Counsel. 15 USC 77ooo – Duties and Responsibility of the Trustee The issuer, or any entity it controls, cannot serve as trustee.
When a corporate issuer files for Chapter 11 bankruptcy, the goal is reorganization rather than liquidation. The company files a plan of reorganization that classifies all claims and specifies how each class will be treated.13United States Courts. Chapter 11 – Bankruptcy Basics Bondholders whose claims are impaired, meaning they’ll receive less than the full value owed, get to vote on whether to accept the plan.
Recovery varies widely. Secured bondholders, whose bonds are backed by specific assets, typically recover more than unsecured bondholders. In many corporate defaults, unsecured bondholders receive a combination of new debt, equity in the reorganized company, or cash at a fraction of the original face value. Recovery rates for investment-grade bonds that default tend to be higher than for high-yield bonds, but nothing is guaranteed. The process can take months or years, and the bond’s market price during bankruptcy often trades at steep discounts.
Debt Securities Versus Equity Securities
It’s worth being clear on what a debt security is not. The difference between a debt security and an equity security comes down to one question: are you a lender or an owner? A bondholder lends money and expects repayment on a schedule. A stockholder buys a piece of the company and hopes it grows in value.
Debt holders receive fixed interest payments regardless of how well the company performs. Stockholders receive dividends only if the board of directors declares them, and the value of their shares depends entirely on the company’s earnings and market sentiment. In a good year, equity holders can earn far more than bondholders. In a bad year, equity holders can lose everything while bondholders keep collecting interest as long as the company stays solvent.
In bankruptcy, this distinction becomes starkly real. Secured creditors are paid first, then unsecured creditors, then equity holders get whatever remains. In practice, stockholders in a bankrupt company often receive nothing. That priority structure is the single biggest reason debt securities are considered lower risk than equity.
Stockholders typically get voting rights and a say in corporate governance. Bondholders get no vote and no management influence. A bondholder’s protections come from the bond indenture, a legal contract that can restrict the issuer from taking on excessive additional debt, selling key assets, or making distributions to shareholders that would jeopardize the company’s ability to repay its bonds. Those covenants function as guardrails, giving bondholders a kind of indirect control over the issuer’s riskier impulses.