Is municipal bond interest tax-free? Do I owe federal or state tax on muni bond income?

Municipal bond interest occupies a unique position in the tax code — it's partially tax-advantaged, but with important caveats many investors don't fully understand.

Federal income tax:

Interest income from most municipal bonds issued by U.S. states, cities, counties, and local governments is exempt from federal income tax. This is the primary appeal of munis for high-income investors. You'll see the tax-exempt interest reported in Box 8 of your 1099-INT, and it flows to Schedule B but is excluded from your taxable income.

State income tax — it depends:

State tax treatment varies significantly:

• Your own state's bonds: Most states exempt interest on bonds issued by their own government (intra-state bonds). So if you're a California resident holding California muni bonds, you generally pay no California state income tax on the interest.
• Out-of-state bonds: Most states do tax interest from bonds issued by other states. A New York resident holding Texas municipal bonds will likely owe New York state tax on that interest.
• Exceptions: A handful of states (like Illinois, Wisconsin, and Iowa at various times) have taxed all municipal bond interest, including in-state bonds. Check your specific state's rules.
• U.S. territories: Interest from bonds issued by Puerto Rico, Guam, and the U.S. Virgin Islands is triple-tax-exempt (federal + state + local) for all U.S. investors, regardless of where they live.

Alternative Minimum Tax (AMT):

Some municipal bonds — specifically "private activity bonds" used to fund projects like airports, certain housing, or industrial facilities — are subject to the federal AMT. These bonds pay slightly higher yields to compensate. If you're subject to AMT (Form 6251), this interest could increase your AMT liability. Look for "specified private activity bond interest" in Box 9 of your 1099-INT.

Capital gains:

If you sell a muni bond at a gain, that capital gain is fully taxable at ordinary capital gain rates. The tax exemption only applies to the interest income, not appreciation in the bond's market value.