Tax-exempt securities are debt instruments whose interest income is excluded from federal income tax, and often from state and local tax as well. The bulk of the market is municipal bonds issued by states, cities, counties, and their agencies, but the category also covers certain U.S. savings bonds used for education and qualified private activity bonds issued for public-purpose projects run by private entities. The appeal is arithmetic: for someone in the 2026 top federal bracket of 37%, a tax-exempt bond yielding 4% delivers the same after-tax return as a taxable bond paying about 6.35%.
The exemption is narrower than the label suggests. It applies to interest, not to capital gains or market discount, and even the exempt interest can raise your Social Security tax bill and your Medicare premiums. The sections below work through what qualifies, what doesn’t, and where the tax shows up anyway.
What Counts as a Tax-Exempt Security
Municipal bonds are the core of the category. They come in two structures: general obligation bonds, backed by the taxing power of the issuing government, and revenue bonds, repaid only from the income of a specific project such as a toll road, water system, or airport. Revenue bonds carry more risk because there’s no broader tax base behind them if the project underperforms.
Series EE and Series I savings bonds issued after 1989 can generate tax-exempt interest under the Education Savings Bond Program. If you redeem the bonds and use the proceeds for qualified higher education expenses in the same year, you can exclude some or all of the interest from federal income tax. You must have been at least 24 years old when the bond was issued, and the exclusion phases out at income levels the IRS updates each year.1Bureau of the Fiscal Service. Using Savings Bonds for Education This benefit is aimed at middle-income families paying for college; high earners are usually phased out entirely.
Qualified private activity bonds fund projects managed by private entities but serving a public purpose, such as affordable housing, nonprofit hospitals, and certain industrial facilities. They qualify for tax-exempt treatment only if they satisfy specific tests in the Internal Revenue Code governing how much of the bond proceeds benefit private parties.2Internal Revenue Service. Publication 4078 – Tax-Exempt Private Activity Bonds Even when they qualify, many of them trigger the alternative minimum tax, which is covered further down.
When the Federal Exemption Doesn’t Apply
Federal law excludes from gross income the interest on any state or local bond that meets certain requirements.3Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds A “state or local bond” means a debt obligation of a state, the District of Columbia, a U.S. territory, or any political subdivision of those entities: counties, cities, school districts, port authorities, and similar bodies.
Three categories of bonds lose the exemption. First, private activity bonds that fail the qualifying tests in the Code. Second, arbitrage bonds, where the issuer invests the borrowed proceeds in higher-yielding securities instead of using them for the stated public purpose.4Office of the Law Revision Counsel. 26 USC 148 – Arbitrage Bonds Third, bonds not issued in registered form, a compliance rule aimed at preventing anonymous bearer bonds.
The arbitrage rule matters to investors because violations can reach back to hurt bondholders. If a city borrows at 4% and parks the proceeds in a 5% investment, that spread is arbitrage profit the federal government prohibits. Issuers must spend the money within a reasonable temporary period or rebate the excess to the U.S. Treasury. When issuers fail to comply, the IRS can reclassify the bonds as taxable from the date of issuance, and investors end up owing tax on interest they believed was exempt.
State and Local Tax Treatment
Most states exempt interest on bonds issued within their own borders from state income tax. When a bond is exempt from federal, state, and local income tax at the same time, investors call it triple tax-exempt. That’s the incentive state legislatures intend, and it’s why in-state buyers dominate many state issues.
Out-of-state bonds are treated differently. The federal exemption still applies, but many states tax the interest as ordinary income. A few states have no income tax, and a handful exempt all municipal bond interest regardless of the issuer’s location. Two investors holding the same bond can see materially different after-tax returns based only on where they live. Check your state’s rule before assuming an out-of-state municipal bond is fully tax-free.
Reporting Tax-Exempt Interest on Your Return
Tax-exempt interest doesn’t raise your regular federal income tax, but you still have to report it. The total goes on Line 2a of Form 1040.5Internal Revenue Service. 2025 Instructions for Form 1040 Your broker or bank reports the amount to you in Box 8 of Form 1099-INT, with any specified private activity bond interest broken out in Box 9.6Internal Revenue Service. Instructions for Forms 1099-INT and 1099-OID If you own a mutual fund holding municipal bonds, the exempt-interest dividends appear in Box 12 of Form 1099-DIV.
The IRS collects this figure because it feeds into other calculations that can increase what you owe. Skipping the entry or misreporting the amount can trigger a notice or cause you to understate the tax on Social Security benefits and your Medicare premiums.
Where the “Tax-Free” Label Breaks Down
The exemption applies to the interest on qualifying bonds. It doesn’t shield the rest of your tax picture from that interest, and it doesn’t shield other kinds of income the same bonds can produce.
Social Security Benefits
Whether your Social Security benefits are taxed depends on your combined income, defined as adjusted gross income plus one-half of your Social Security benefits plus your tax-exempt interest.7Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits If the total exceeds the base amount for your filing status, up to 50% or 85% of your benefits become taxable.8Internal Revenue Service. Social Security Income A large municipal portfolio can push you across the threshold even though the bond interest itself isn’t taxed. It acts as phantom income that makes other income taxable.
Medicare IRMAA Surcharges
Medicare Part B and Part D premiums include an Income-Related Monthly Adjustment Amount for higher-income beneficiaries. The Social Security Administration calculates it using modified adjusted gross income, which is AGI from Line 11 plus tax-exempt interest from Line 2a.9Social Security Administration. HI 01101.010 – Modified Adjusted Gross Income (MAGI) The income counted is from two years earlier, so your 2024 return sets your 2026 premiums. For 2026, IRMAA begins when single filers exceed $109,000 and joint filers exceed $218,000, and the top-tier surcharge runs close to $7,000 per person per year.
Alternative Minimum Tax on Private Activity Bonds
The AMT runs a parallel calculation alongside the regular tax. If it produces a higher liability, you pay the difference. Interest on specified private activity bonds is added back in the AMT calculation.10Office of the Law Revision Counsel. 26 USC 57 – Items of Tax Preference The term generally covers private activity bonds issued after August 7, 1986, whose interest is otherwise excluded from gross income, with carve-outs for certain housing bonds, qualified 501(c)(3) bonds, and qualified veterans’ mortgage bonds. Box 9 of Form 1099-INT tells you how much of your interest is in this category. If the amount is meaningful and you’re near AMT territory, run Form 6251 before buying more.
Capital Gains and Market Discount
The exemption covers interest, not gains. If you sell a municipal bond for more than you paid, the profit is a capital gain and is taxable at the usual rates. Bonds bought on the secondary market below par create an additional wrinkle. The difference between purchase price and face value is market discount, and the IRS generally taxes gain attributable to that discount as ordinary income rather than capital gain when you sell or the bond matures.11Internal Revenue Service. Publication 550 – Investment Income and Expenses A de minimis rule lets small discounts through: if the discount is less than 0.25% of face value multiplied by the years remaining to maturity, the discount is treated as zero and any gain is a capital gain.
Original issue discount, where the issuer sold the bond below face value at issuance, follows different rules. For tax-exempt OID bonds, the discount accretes over the life of the bond and is generally treated as additional tax-exempt interest. Your broker reports tax-exempt OID in Box 11 of Form 1099-OID.
One Place It Really Doesn’t Count
The 3.8% Net Investment Income Tax that applies to higher-income taxpayers explicitly excludes tax-exempt interest from net investment income.12Internal Revenue Service. Questions and Answers on the Net Investment Income Tax That’s a genuine break, not a hidden hit.
Comparing Yields to Taxable Bonds
A municipal bond at 3.5% and a corporate bond at 5% aren’t directly comparable because the corporate interest is taxed. The tax-equivalent yield formula puts them on the same footing:
Tax-equivalent yield = Tax-exempt yield ÷ (1 − your marginal tax rate)
At the 37% federal bracket for 2026, a 3.5% municipal bond has a tax-equivalent yield of 3.5% ÷ 0.63, or about 5.56%.13Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 That beats the 5% corporate bond after tax. At the 24% bracket, the same municipal bond’s tax-equivalent yield drops to roughly 4.61%, and the corporate bond wins.
If you’re also skipping state and local tax on an in-state bond, add those rates to the denominator; the advantage widens for residents of high-tax states. The formula ignores AMT exposure, so if you hold specified private activity bonds and are subject to the AMT, your real after-tax yield is lower than the number the formula produces.