Nuveen Municipal Bond Funds: Federal, State, and AMT Rules

Nuveen municipal bond fund taxes work on a split: the interest income the fund pays you as exempt-interest dividends is generally free from federal income tax, and often free from your state’s income tax if the bonds were issued in your state, but capital gains from selling shares or from the fund’s own trading are fully taxable, and the “tax-free” interest still counts in formulas that decide how much of your Social Security is taxed and what you pay for Medicare.

Federal Tax Treatment of the Dividends

Interest on bonds issued by state and local governments is excluded from gross income under federal law.¹ Nuveen’s municipal bond funds hold portfolios of those bonds and pass the interest to shareholders as exempt-interest dividends, which keep their tax-free character in your hands.

You still have to report them. The total goes on Form 1040, Line 2a, using the figure from Box 12 of your Form 1099-DIV.² The line is informational for federal income tax purposes, but the same number gets pulled into other calculations that do affect what you owe.

State Income Tax Depends on Where the Bonds Were Issued

Most states exempt interest from bonds issued within their own borders and tax interest from out-of-state bonds at ordinary state rates. That is why Nuveen offers state-specific funds for high-tax states such as California, New York, and New Jersey: a resident holding a single-state fund can capture both the federal and state exemption on essentially all of the income.

Hold a national municipal bond fund and a portion of the income will trace back to bonds issued elsewhere, taxable on your state return. Nuveen publishes an annual tax information supplement that breaks each fund’s income down by state of origin. If 72 percent of a fund’s income came from bonds issued in your state, roughly 72 percent of your Box 12 amount is potentially exempt at the state level.

A few states have no income tax, which makes the state exemption moot. A few others tax municipal bond interest regardless of where it was issued. Check your state’s rule before paying up for the narrower diversification of a single-state fund.

AMT Exposure From Private Activity Bonds

Some bonds held inside Nuveen’s funds finance projects with a significant private component, such as airports, housing developments, and industrial facilities. Interest on private activity bonds issued after August 7, 1986, is a tax preference item for Alternative Minimum Tax purposes.³ Your share appears in Box 13 of the 1099-DIV.⁴

For tax year 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, phasing out starting at $500,000 and $1,000,000 respectively.⁵ Income above your exemption is taxed at 26 percent, rising to 28 percent above a higher threshold. Most shareholders won’t owe AMT, but a large position in a fund with heavy private activity bond exposure is worth running through the calculation.

Capital Gains Are Not Exempt

The exemption covers interest, nothing else. Sell your Nuveen fund shares for more than you paid and the gain is a taxable capital gain. Shares held longer than a year get long-term rates; a year or less means ordinary income treatment. Long-term rates for 2026:

0 percent on taxable income up to $49,450 single or $98,900 joint
15 percent from those thresholds up to $545,500 single or $613,700 joint
20 percent above those amounts

You can also owe capital gains tax without selling anything yourself. When the fund’s managers sell bonds internally at a profit, the realized gains flow through as capital gain distributions, taxable in the year paid whether you took the cash or reinvested. This trips up investors who assume “tax-free municipal bond fund” means the whole account is tax-free. The exemption is on the interest.

Losses on sales can offset gains from other investments, and net losses can offset up to $3,000 of ordinary income per year, with the rest carried forward.

The 3.8 Percent Net Investment Income Tax

A separate 3.8 percent surtax applies to net investment income when modified adjusted gross income exceeds $200,000 for single filers or $250,000 for joint filers.⁶ Those thresholds are fixed in the statute with no inflation adjustment.

Tax-exempt interest is excluded from net investment income, so your Nuveen exempt-interest dividends don’t feed the surtax.⁷ Capital gain distributions from the fund and gains on selling your shares do count. Above the MAGI threshold, those gains face both the regular capital gains rate and the 3.8 percent surtax on top.

How the “Tax-Free” Interest Affects Social Security Taxation

This is where the exemption quietly costs retirees money. Exempt-interest dividends don’t add to taxable income, but federal law adds them back when calculating how much of your Social Security benefit is taxable. The statute defines the calculation to include tax-exempt interest.⁸

The formula: take your adjusted gross income, add your tax-exempt interest, add half of your Social Security benefits. If the total exceeds $25,000 single or $32,000 joint, up to 50 percent of benefits are taxable. At higher levels, up to 85 percent.⁸ Those thresholds have never been adjusted for inflation, so most retirees with meaningful investment income cross them.

A large municipal bond fund position can push you from the 50 percent tier into the 85 percent tier. The exempt-interest dividends stay untaxed, but they indirectly cause a bigger slice of your Social Security to become taxable.

Impact on Medicare Premiums

Medicare Part B and Part D premiums include an income-related surcharge, IRMAA, that uses the same modified adjusted gross income calculation, which counts tax-exempt interest.⁹ The surcharge is set from the tax return filed two years earlier, so your 2024 return governs your 2026 premiums.

In 2026, married couples filing jointly with MAGI at or below $218,000 pay the standard Part B premium of $202.90 a month. Above that, surcharges rise in five tiers, from $1,148 per year at the first tier to $6,936 per year at joint MAGI of $750,000 and above. Single filers hit the same surcharge amounts at roughly half the income thresholds, starting at $109,000.⁹ Because Nuveen’s exempt-interest dividends count in MAGI, a sizable position can bump you into a higher tier. If your total MAGI sits near a boundary, check before adding to the position.

Wash Sales When Harvesting Losses

Sell shares at a loss and you can generally deduct that loss, but the wash sale rule disallows it if you buy substantially identical securities within 30 days before or after the sale.¹⁰ The disallowed loss shifts into the cost basis of the replacement shares, so the benefit is deferred, not lost.

The IRS has never drawn a bright line for what makes two mutual funds “substantially identical.” Swapping one Nuveen national municipal fund for another Nuveen national fund with nearly identical holdings would likely trigger the rule. Moving to a state-specific fund, or to a competitor’s fund with meaningfully different holdings, is less likely to cause a problem, but it is a judgment call. Talk to a tax professional before rebuying similar exposure inside the 30-day window.

Forms, Boxes, and What to Keep

Two documents drive the filing. The first is Form 1099-DIV.¹¹ The boxes that matter for a municipal bond fund holder:

Box 12, total exempt-interest dividends⁴
Box 13, the portion of Box 12 attributable to private activity bonds, used for AMT
Box 2a, capital gain distributions from the fund’s internal trading

The second is Nuveen’s annual tax information supplement, which breaks each fund’s interest income down by the state where the bonds were issued. Use it to figure how much of your Box 12 amount qualifies for your home state’s exemption.

On the federal return, Box 12 goes on Form 1040, Line 2a.² Capital gain distributions go on Schedule D or directly on the 1040 depending on whether you have other gains or losses. If your total taxable interest or ordinary dividends across all accounts exceeded $1,500, file Schedule B as well.¹² Keep the 1099-DIV and the Nuveen supplement together; state auditors ask about the state breakdown.

1
Office of the Law Revision Counsel. 26 US Code 103 – Interest on State and Local Bonds
2
Internal Revenue Service. Instructions for Form 1040
3
Office of the Law Revision Counsel. 26 USC 57 – Items of Tax Preference
4
Internal Revenue Service. Form 1099-DIV – Dividends and Distributions
5
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
6
Office of the Law Revision Counsel. 26 USC 1411 – Imposition of Tax
7
Internal Revenue Service. Topic No 559 Net Investment Income Tax
8
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
9
Social Security Administration. Modified Adjusted Gross Income (MAGI)
10
Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities
11
Internal Revenue Service. About Form 1099-DIV Dividends and Distributions
12
Internal Revenue Service. Instructions for Schedule B Form 1040