Tax-exempt interest income is interest that federal law keeps out of gross income, so it carries no regular federal income tax. The exclusion behind the term is statutory: gross income does not include interest on any State or local bond, except as provided in subsection (b) (26 U.S.C. 103(a)). Exempt is not the same as unreported, and it is not the same as untaxed everywhere. The amount still goes on the return, it can still reach the alternative minimum tax, and the filer’s own state may tax part of it.
What Makes Interest Tax-Exempt
The test is what issued the obligation, not how large the payment was. Section 103 defines its own subject narrowly: a State or local bond is an obligation of a State or political subdivision thereof, and State includes the District of Columbia and any possession of the United States (26 U.S.C. 103(c)). Everyday practice calls those obligations municipal bonds, and State or local bond is the defined term the statute actually works with.
Three classes of bond fall outside the exclusion, each defined elsewhere in the Code. The exclusion does not reach a private activity bond that is not a qualified bond within the meaning of section 141. A bond is a private activity bond if its issue meets both the private business use test and the private security or payment test of section 141(b), or the private loan financing test of section 141(c), and the private business use test is met when more than 10 percent of the issue’s proceeds are to be used for a private business use (26 U.S.C. 141(a), (b)(1)). It does not reach an arbitrage bond within the meaning of section 148 either. And the paragraph headed bond not in registered form withholds the exclusion from any bond unless that bond meets the applicable requirements of section 149 (26 U.S.C. 103(b)).
A mutual fund reaches the same result by a different route. An exempt-interest dividend is treated by the shareholders for all purposes of the subtitle as an item of interest excludable from gross income under section 103(a), which is why fund income arrives already carrying the character (26 U.S.C. 852(b)(5)(B)).
Interest that does not come from a State or local bond never reaches section 103 at all (26 U.S.C. 103(a)). Bank interest, certificate of deposit interest and Treasury interest are ordinary taxable interest federally.
Treasury interest runs the opposite way on the state side, because stocks and obligations of the United States Government are exempt from taxation by a State or political subdivision of a State. That exemption is subject to two exceptions and no others: a nondiscriminatory franchise tax or another nonproperty tax instead of a franchise tax, imposed on a corporation, and an estate or inheritance tax (31 U.S.C. 3124(a)).
Exempt Does Not Mean Unreported
The duty to report it is in the Code, not just in a form instruction. Every person required to file a return under section 6012 for the taxable year shall include on that return the amount of interest received or accrued during the taxable year which is exempt from the tax imposed by chapter 1 (26 U.S.C. 6012(d)).
The payer reports it in box 8 of Form 1099-INT, with the portion subject to the alternative minimum tax broken out in box 9, an amount included in box 8 rather than added to it (IRS, Form 1099-INT). A mutual fund or other regulated investment company reports the same money as exempt-interest dividends in box 12 of Form 1099-DIV, with the alternative minimum tax portion in box 13, again included in box 12 (IRS, Form 1099-DIV). The filer then shows the total at line 2a of Form 1040, directly above taxable interest at line 2b (IRS, Form 1040 (2025)).
That reporting line does work elsewhere on the return. Tax-exempt interest is added back in some modified adjusted gross income computations and left out of others, provision by provision, so the same excluded amount can raise one threshold test and leave another untouched. Section 86 is the one a preparer meets most. Modified adjusted gross income there is adjusted gross income increased by the amount of interest received or accrued by the taxpayer during the taxable year which is exempt from tax, so a client’s municipal interest can push more of their Social Security benefits into gross income without being taxed itself (26 U.S.C. 86(b)(2)).
The State Layer Is a Separate Question
Federally exempt does not mean exempt in the filer’s own state, and each state writes the rule for itself. North Carolina allows a deduction for interest on its own obligations to the extent that income is already in federal taxable income and adjusted gross income, and it requires taxpayers who received interest on notes and bonds from other states to add that interest back on Form D-400 Schedule S, Part A, because it was never in the federal figure. Notes and bonds issued by Guam, Puerto Rico and the US Virgin Islands are not subject to that adjustment (North Carolina Department of Revenue, Interest Income).
That is one state’s answer, so a preparer reads the client’s own state instruction rather than carrying North Carolina’s treatment across. The practical consequence is that a single box 8 total has to be split by issuing state before a state return that requires the adjustment can be prepared, and Form 1099-INT does not carry that split. Box 14 is the tax-exempt and tax credit bond CUSIP number, and boxes 15 through 17 are the state withholding boxes, carrying the state, the state identification number and the state tax withheld (IRS, Form 1099-INT).
The AMT Preference on Specified Private Activity Bonds
Interest on specified private activity bonds is an item of tax preference, reduced by any deduction, not allowable in computing the regular tax, which would have been allowable if the interest were includible in gross income (26 U.S.C. 57(a)(5)(A)).
The defined term is narrower than private activity bond. A specified private activity bond is any private activity bond as defined in section 141, issued after August 7, 1986, whose interest is not includible in gross income under section 103. The definition then excludes a qualified 501(c)(3) bond as defined in section 145, certain housing bonds, and a refunding bond where the refunded bond was issued before August 8, 1986 (26 U.S.C. 57(a)(5)(C)). An exempt-interest dividend is pulled into the same treatment to the extent of its proportionate share of the interest on those bonds received by the company paying the dividend (26 U.S.C. 57(a)(5)(B)).
On the return the preference lands at line 2g of Form 6251, headed interest from specified private activity bonds exempt from the regular tax (IRS, Form 6251 (2025)).
Interest Paid to Carry Exempt Bonds Is Not Deductible
No deduction is allowed for interest on indebtedness incurred or continued to purchase or carry obligations the interest on which is wholly exempt from the taxes imposed by the subtitle (26 U.S.C. 265(a)(2)). The paragraph beside it denies expenses allocable to wholly exempt income, and a later paragraph reaches interest on debt incurred to carry shares in a regulated investment company that pays exempt-interest dividends (26 U.S.C. 265(a)).
The trap is that the disallowance follows purpose, and the information returns report the interest received rather than the borrowing behind the holding. It surfaces only when someone sets the client’s debt beside the client’s portfolio.
How the Numbers Move Through the Forms
Say a North Carolina client’s Form 1099-INT shows a tax-exempt interest total for the year, part of it from specified private activity bonds, and part of it on bonds issued by states other than North Carolina, with none of that part from Guam, Puerto Rico or the US Virgin Islands.
Form 1099-INT box 8 tax-exempt interest 9,000
Form 1099-INT box 9 specified private activity bond interest 1,500 (inside box 8)
Form 1040 line 2a tax-exempt interest 9,000
Form 1040 line 2b taxable interest 0
Form 6251 line 2g specified private activity bond interest 1,500
Form D-400 Sch S Pt A other states' obligations 4,000Nothing is counted twice. The box 9 figure is a slice of box 8, so it appears once on the reporting line and then once more only as a preference. The state add-back is a different slice of the same box 8 total, cut by who issued the bond rather than by what kind of bond it is, so the two slices can overlap and neither one is added to the other.
What It Is Commonly Confused With
Tax-exempt interest income is not tax-deferred income. A deferral moves recognition to a later period, so the tax arrives later. The exclusion removes the amount from gross income, so regular federal income tax on it never arrives (26 U.S.C. 103(a)).
Common Questions
Line 2a is a reporting line rather than a taxable one. The amount shown there is excluded from gross income for regular tax, so it does not feed taxable income, and it sits directly above taxable interest at line 2b so the two are never merged (IRS, Form 1040 (2025)).
Read it off the information returns rather than the account statements. Box 8 of Form 1099-INT carries interest paid on qualifying obligations (IRS, Form 1099-INT), and box 12 of Form 1099-DIV carries exempt-interest dividends paid by a mutual fund or other regulated investment company (IRS, Form 1099-DIV).
Interest a Code provision keeps out of gross income, so no regular federal income tax is charged on it. The provision that produces it is section 103, which excludes interest on a State or local bond, and the income can reach the filer straight from the bond or through a fund that passes the character on (26 U.S.C. 103(a), 26 U.S.C. 852(b)(5)).
No dollar amount makes interest tax-free. The exclusion attaches to the obligation and not to the size of the payment, so a large payment on a qualifying State or local bond is excluded while a small payment on a bank account or a Treasury is not (26 U.S.C. 103(a)). The reporting floors on the information returns are filing triggers for the payer, and they never make an amount tax-free.
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