Tax-free municipal bonds are loans you make to a state or local government that pay you interest exempt from federal income tax under 26 U.S.C. § 103.1Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds That exemption can make a bond paying 4% worth more after taxes than a corporate bond paying 5% or 6%, depending on your bracket. But “tax-free” is a narrower label than it sounds: capital gains on munis are fully taxable, some bonds trigger the Alternative Minimum Tax, and the interest counts toward the income figures that decide how much of your Social Security is taxed and what you pay for Medicare.
What You’re Actually Buying
When you buy a municipal bond, you’re lending money to a government entity. That entity promises to pay you interest on a set schedule and return your principal at maturity. Issuers include states, cities, counties, school districts, and special-purpose authorities. The proceeds fund roads, schools, water systems, hospitals, and similar public projects.
Two structures dominate the market. General obligation bonds are backed by the issuer’s full taxing power; if the city needs to raise property taxes to make the payments, it can, and voters usually have to approve the issuance. That broad taxing authority makes general obligation bonds among the safest municipal debt available. Revenue bonds are repaid from a specific income stream tied to what the bond financed: tolls from a highway, fees from a water utility, charges from a public hospital. If that project doesn’t generate enough money, the issuer typically has no obligation to tap general tax revenue to cover bondholders. Revenue bonds carry more risk than general obligation bonds and usually pay slightly higher interest to compensate.
What the Federal Exemption Covers
Section 103 of the Internal Revenue Code says gross income does not include interest on any state or local bond, with limited exceptions.1Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds The exemption is automatic. You don’t file a form or make an election; the interest simply doesn’t enter your taxable income for federal purposes.
The exemption covers only interest. Any profit from selling a bond before maturity is a capital gain and is taxed like any other investment gain. Bonds held longer than a year qualify for long-term rates of 0%, 15%, or 20%. Bonds held a year or less are taxed at ordinary rates, up to 37% for 2026.
The State Tax Layer
Most states also exempt interest on bonds issued within their own borders from state income tax, producing what the industry calls “double-exempt” income. A New York resident buying a New York authority bond generally owes no federal or state tax on the interest. A few cities with their own income taxes extend the treatment further, making the interest “triple-exempt.”
Buy an out-of-state bond and your home state usually taxes the interest at its regular income rate. State rates run from zero in no-income-tax states up to over 13% in the highest-tax states, so residents of high-tax states often tilt heavily toward in-state issues.
Comparing a Muni Yield to a Taxable Yield
A 4% muni and a 4% corporate bond are not the same deal. To compare them honestly, calculate the tax-equivalent yield:
Tax-Equivalent Yield = Tax-Exempt Yield ÷ (1 − Your Marginal Tax Rate)
In the 32% federal bracket, a 4% muni equals 4% ÷ (1 − 0.32) = 5.88% taxable. A corporate bond would need to pay nearly 6% to leave you with the same after-tax return. In the 24% bracket, the same muni equals about 5.26% taxable. The higher your bracket, the more valuable the exemption, which is why munis are most attractive to higher-income investors.
If your state also exempts the interest, use your combined federal-plus-state marginal rate. Someone in the 37% federal bracket living in a state with a 10% income tax could see a tax-equivalent yield well above 7% on that same 4% muni.
When “Tax-Free” Isn’t Fully Tax-Free
Several situations pull muni income back into your tax return even though the bond itself is tax-exempt.
Market Discount
Buy a bond on the secondary market for less than face value and the discount can be taxed as ordinary income, not capital gain, when you sell or redeem. The de minimis threshold is 0.25% of face value multiplied by the number of full years to maturity. For a $1,000 bond with 10 years left, that cutoff is $25. Buy it for $960 and the $40 discount is taxed as ordinary income at redemption. Stay above the threshold and the gain is treated as capital gain instead.
Bond Premium
If you pay more than face value for a tax-exempt bond, you must amortize that premium over the remaining life of the bond, reducing your cost basis each year.2Office of the Law Revision Counsel. 26 USC 171 – Amortizable Bond Premium Unlike taxable bonds, where amortization gives you an annual deduction, the IRS does not allow any deduction for the amortized premium on tax-exempts. You still track it, because it adjusts basis and determines the gain or loss when you sell or the bond matures. Brokers typically handle the math and report it on your statement.
Original Issue Discount
Some munis are issued below face value. For tax-exempt bonds, you generally don’t include the accruing discount in income, but you do add it to your cost basis over time.3Internal Revenue Service. Guide to Original Issue Discount (OID) Instruments Getting the basis right matters when you sell.
Private Activity Bonds and the AMT
Some munis are classified as private activity bonds because a significant share of the proceeds finances projects with private business involvement, like an airport terminal leased to airlines or a stadium used by a professional sports team. The Internal Revenue Code defines the category through tests measuring how much of the bond’s proceeds flow to private use and private payments.4Office of the Law Revision Counsel. 26 USC 141 – Private Activity Bond, Qualified Bond
Interest on most private activity bonds is still exempt from regular federal income tax, but it counts as a preference item for the Alternative Minimum Tax under 26 U.S.C. § 57(a)(5).5Office of the Law Revision Counsel. 26 USC 57 – Items of Tax Preference If your AMT calculation pushes you above the exemption threshold, that “tax-free” interest becomes partially taxable. For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, with phaseouts beginning at $500,000 and $1,000,000.6Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Those amounts are high enough that most investors won’t trigger the AMT, but people with large private activity holdings should run the numbers. Certain categories are carved out from AMT treatment entirely, including qualified 501(c)(3) bonds used by nonprofit hospitals and universities and bonds financing qualified residential rental projects. Your brokerage statement or the offering document will say whether a bond is subject to AMT.
The Retiree Traps: Social Security and Medicare
Muni interest doesn’t hit your taxable income line, but two federal programs treat it as if it does. This is where the “tax-free” label costs some retirees real money.
Social Security Taxation
The IRS calculates a figure called combined income to decide how much of your Social Security is taxable: half your benefits, plus all other income, plus tax-exempt interest. If combined income exceeds $25,000 for single filers or $32,000 for married couples filing jointly, up to 50% of benefits become taxable. Above $34,000 or $44,000, up to 85% are taxable.7Internal Revenue Service. Publication 915 – Social Security and Equivalent Railroad Retirement Benefits Those thresholds have never been adjusted for inflation, so they catch more retirees every year. A retiree assuming muni interest was invisible to the IRS can find thousands in benefits newly taxed.
Medicare Part B and Part D Surcharges
Medicare uses modified adjusted gross income, which includes tax-exempt interest, to determine whether you pay an Income-Related Monthly Adjustment Amount on top of the standard Part B premium. For 2026, the standard Part B premium is $202.90 per month. Once MAGI crosses $109,000 (single) or $218,000 (joint), surcharges kick in and can push the monthly premium as high as $689.90.8Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles At the highest bracket, a couple with MAGI of $750,000 or more pays $487.00 per person per month in surcharges alone. A large muni portfolio can push a retiree into a higher IRMAA bracket even though the interest itself isn’t taxed.
Reporting the Interest on Your Return
Your broker reports tax-exempt interest on Form 1099-INT, Box 8, if the total is $10 or more for the year.9Internal Revenue Service. Instructions for Forms 1099-INT and 1099-OID You won’t owe federal tax on this amount, but the IRS still requires you to report it on Line 2a of Form 1040.10Internal Revenue Service. Instructions for Form 1040 Skipping this line is one of the most common muni errors. The IRS already knows what your broker reported, and a missing entry can generate a notice even though no tax is due.
For state returns, you’ll need to know where each bond was issued. In-state interest is usually exempt; out-of-state interest usually gets added to state taxable income. Year-end brokerage statements break this out, and muni fund companies publish a state-by-state allocation each year so shareholders can calculate the taxable portion. If any of your bonds are private activity bonds subject to AMT, that interest appears in Box 9 of Form 1099-INT and feeds Form 6251 if you’re required to file it.
Risks Worth Understanding
Munis are among the safest fixed-income investments, but they carry real risks.
Credit risk. Defaults are rare and recovery rates on defaulted munis have historically been much higher than on corporates. “Rare” isn’t “never,” though; Detroit and Puerto Rico are the standing reminders. Sticking to investment-grade bonds, rated BBB− or higher by S&P (Baa3 or higher by Moody’s), keeps you in the safest segment of an already safe asset class.
Interest rate risk. When prevailing rates rise, existing bond prices fall, and the longer the remaining term, the larger the swing. A 20-year bond loses considerably more market value from a 1% rate increase than a 5-year bond. Holding to maturity avoids the price hit, since you get face value back, but selling early in a rising-rate environment can produce a loss.
Call risk. Many munis include a call provision letting the issuer redeem the bond before maturity, typically after 10 years.11Investor.gov. Callable or Redeemable Bonds Issuers call when rates drop so they can refinance cheaper. That’s the wrong time for you as the holder: the high-interest bond disappears and you reinvest at lower rates. Check the call date and call price before buying. Sinking fund provisions can also retire portions of an issue on a set schedule.
Liquidity risk. The muni market is enormous but fragmented across roughly a million outstanding issues, and many trade infrequently. Bid-ask spreads can be wide for smaller or less-known issuers, and selling a thinly traded bond in a hurry usually means accepting a worse price.
How to Buy Them
Three routes cover most investors.
Individual Bonds
Individual munis are typically sold in minimum increments of $5,000 face value.12FINRA. Municipal Securities New issues come through brokers participating in the underwriting; secondary market bonds trade at prices driven by interest rates, credit, and time to maturity. The MSRB’s Electronic Municipal Market Access system (EMMA, at emma.msrb.org) is a free tool worth bookmarking. It shows real-time trade prices, official disclosure documents, credit ratings, and upcoming new issues for virtually every outstanding muni.13MSRB. About EMMA Checking recent trades on EMMA before placing an order helps you avoid overpaying on the secondary market, where pricing transparency has historically been weaker than in stocks.
Municipal Bond Funds and ETFs
Mutual funds and ETFs holding muni portfolios let you invest with less capital and get instant diversification across dozens or hundreds of issuers. You give up the ability to hold a specific bond to maturity, and share prices fluctuate daily. Expense ratios typically run from around 0.05% for passive index ETFs to 0.50% or more for actively managed funds. If you live in a high-tax state, check whether the fund holds in-state bonds for state exemption; many companies offer state-specific funds for California, New York, and New Jersey residents. National funds diversify more broadly but include out-of-state interest that your state may tax.
Separately Managed Accounts
For larger portfolios, separately managed accounts build a custom set of individual bonds around your state, bracket, maturity needs, and credit preferences. You own the bonds directly, which allows tax-loss harvesting and lets you hold specific bonds to maturity. Fees usually run 0.20% to 0.50% of assets annually.