A bond is a loan you make to a government or company in exchange for regular interest payments and the return of your principal when the bond matures. Bonds and other fixed-income investments play a specific role in a portfolio: they provide income, reduce volatility, and tend to hold value better than stocks when markets fall. Understanding how bonds work — and why their prices move opposite to interest rates — is foundational to building a balanced portfolio.
How Bonds Work
When you buy a bond, you are lending money to the issuer — a government, municipality, or corporation. In return, the issuer promises to pay you a fixed interest rate (the coupon) at regular intervals, typically twice a year, and to return the face value (the principal) when the bond reaches its maturity date. A 10-year Treasury bond with a face value of $10,000 and a 4% coupon, for example, pays $400 per year in interest and returns $10,000 at the end of 10 years.
The Inverse Relationship Between Bonds and Interest Rates
The most important — and most counterintuitive — fact about bonds is that their prices move opposite to interest rates. When rates rise, existing bond prices fall. When rates fall, existing bond prices rise. The reason: if you hold a bond paying 3% and new bonds are being issued at 5%, your 3% bond is less attractive and must sell at a discount to compete. This inverse relationship matters most if you plan to sell bonds before maturity. If you hold a bond to maturity, you receive exactly the coupon payments and face value you were promised, regardless of what interest rates do in between.
Duration and Interest Rate Risk
Duration measures how sensitive a bond’s price is to interest rate changes. A bond with a duration of 10 means its price will fall roughly 10% if interest rates rise by 1 percentage point. Longer-maturity bonds have higher duration and more price sensitivity. Short-term bonds and bond funds (duration under 3 years) have much less price risk. This is why bond funds lost significant value in 2022 when the Federal Reserve raised rates sharply — long-duration bond funds fell 20% or more while short-term bond funds fell only a few percent. Understanding the duration of a bond fund before you buy it is more important than most investors realize.
Yield and Yield to Maturity
A bond’s yield is its annual interest payment divided by its current market price. When a bond trades at par (its face value), the yield equals the coupon rate. When it trades at a discount (below face value), the yield is higher than the coupon rate. When it trades at a premium (above face value), the yield is lower. Yield to maturity (YTM) accounts for not just the coupon payments but also the gain or loss you’ll experience if the bond price is currently above or below face value. YTM is the more complete measure of what a bond will actually return if held to maturity.
Types of Bonds
Different bond types carry different levels of credit risk, offer different tax treatment, and serve different purposes in a portfolio.
U.S. Treasury Bonds and Bills
Treasury securities are issued by the federal government and are considered the safest bonds available — backed by the full faith and credit of the U.S. government. Treasury bills mature in under a year, Treasury notes mature in 2 to 10 years, and Treasury bonds mature in 20 to 30 years. Interest from Treasuries is exempt from state and local income tax. I Bonds — inflation-indexed savings bonds sold directly by TreasuryDirect — gained attention in 2022 when their rate briefly exceeded 9%. They are limited to $10,000 per person per year but carry zero default risk and have no interest rate risk if held for the full term.
Municipal Bonds
Municipal bonds (munis) are issued by state and local governments to fund infrastructure, schools, and other public projects. Their key advantage: interest is generally exempt from federal income tax and often exempt from state taxes for residents of the issuing state. This tax exemption makes munis most valuable for investors in high federal and state tax brackets. The after-tax yield of a muni can exceed that of a taxable bond with a higher stated rate. Credit quality varies — some municipal issuers are very strong (large states, major cities) while others carry real default risk (smaller districts, financially stressed cities).
Corporate Bonds and Bond Funds
Corporate bonds are issued by companies to raise capital. They pay higher yields than Treasuries to compensate for credit risk — the risk that the company might default. Investment-grade corporate bonds (rated BBB or higher) carry modest default risk; high-yield bonds (also called junk bonds) carry substantially more. For most individual investors, bond funds and ETFs are a more practical way to own corporate bonds than buying individual bonds, because they provide diversification across many issuers. The iShares Core U.S. Aggregate Bond ETF (AGG) and similar funds hold a mix of Treasuries, mortgage-backed securities, and investment-grade corporate bonds.
Individual Bonds vs. Bond Funds
Buying individual bonds guarantees a specific return if held to maturity — you know exactly what you will receive and when. Bond funds, by contrast, have no maturity date and can lose value indefinitely if rates keep rising. The tradeoff: individual bonds require larger minimum investments (often $1,000 to $10,000 per bond) and are harder to diversify across many issuers without significant capital. Bond funds are more accessible and automatically reinvest income, but their price fluctuates with interest rates and they never “mature” back to a fixed value. CD ladders and Treasury ladders are a practical alternative for investors who want the certainty of individual bonds without requiring a brokerage account.
The Role of Bonds in a Portfolio
Bonds serve two main purposes in a diversified portfolio: they generate income, and they reduce volatility. When stocks fall sharply, high-quality bonds often hold their value or rise (in risk-off environments, investors move money into Treasuries, driving prices up). This negative correlation — stocks and bonds moving in opposite directions — is not perfect and has broken down in some periods (notably 2022, when both fell simultaneously as inflation spiked). But over long periods, holding bonds alongside stocks has historically smoothed portfolio volatility significantly, which matters especially for investors who are spending from their portfolio and cannot afford to sell stocks at a 40% loss to meet expenses.
Bonds and Taxes
Interest from most bonds is taxed as ordinary income — the same rate as wages or Social Security — not at the lower capital gains rates that apply to stock dividends. This makes bonds less tax-efficient than stocks in taxable brokerage accounts. For this reason, many financial advisors recommend holding bonds inside tax-deferred accounts (traditional IRAs and 401(k)s) and holding stocks in taxable accounts where qualified dividends and long-term capital gains receive preferential tax treatment. Municipal bonds are the exception — their tax-exempt interest makes them suitable for taxable accounts, particularly for higher-income investors.
Who This Page Is For
- People approaching or in retirement who are adding bonds to their portfolio but are not sure how they work
- Anyone who owned a bond fund in 2022, saw it lose 10% to 20%, and wants to understand why
- Investors trying to decide between individual bonds, CDs, and bond funds for the fixed-income portion of their portfolio
- People who have heard about I Bonds or Treasury bills and want to understand whether they make sense
- Anyone building a retirement income strategy who wants to understand the role bonds play in generating reliable cash flow
What to Do Next
- Look up the duration of any bond funds you currently own — this tells you how much price risk you are carrying and whether the level is appropriate for your time horizon
- Compare the after-tax yield of municipal bonds to taxable bonds if you are in a high tax bracket — the calculator at many brokerage sites can do this automatically
- Consider a CD ladder or Treasury ladder at TreasuryDirect.gov as a way to get bond-like certainty without interest rate risk if you plan to hold to maturity
- Read the Asset Allocation page to understand what percentage of bonds makes sense for your age and risk tolerance
- Review whether your bond holdings are inside tax-advantaged accounts or taxable accounts — bonds are generally more tax-efficient inside an IRA or 401(k)
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