Yes, SCMB is tax exempt at the federal level: the Schwab Municipal Bond ETF pays “exempt-interest dividends” that are excluded from federal gross income under Internal Revenue Code Section 103.1Office of the Law Revision Counsel. 26 US Code 103 – Interest on State and Local Bonds The exemption is narrower than the label suggests. It covers the interest income only. It does not cover capital gains when you sell shares, it applies only partially at the state level, and the “tax-exempt” interest still gets counted in formulas that decide how much of your Social Security is taxed, whether you owe a Medicare surcharge, and whether the Alternative Minimum Tax reaches you.
Federal Income Tax
This is the clean part of the answer. Section 103 excludes interest on state and local bonds from gross income, and that treatment flows through to exempt-interest dividends distributed by a regulated investment company like SCMB.1Office of the Law Revision Counsel. 26 US Code 103 – Interest on State and Local Bonds No federal income tax is due on the dividends themselves.
You still have to report them. Tax-exempt interest goes on Line 2a of Form 1040.2Internal Revenue Service. 1040 (2025) Instructions – Line 2a Your broker sends the IRS the same figure on Form 1099-DIV, so a missing entry can trigger a notice even when no tax is owed.
State Income Tax
SCMB is a nationally diversified fund, holding investment-grade municipal bonds from state and local governments across the country.3Schwab Asset Management. SCMB – Schwab Municipal Bond ETF Most states that levy an income tax exempt interest on bonds issued within the state and tax the rest. So only the slice of SCMB’s dividends attributable to bonds from your home state qualifies for your state’s exemption.
Your brokerage or Schwab publishes a year-end state-by-state allocation showing that percentage. If you live in a no-income-tax state, ignore this section. If you live in a high-tax state and your home-state allocation is a few percent, the state benefit is thin, and a single-state fund or a direct bond may compare better on an after-tax basis. Run the numbers before you buy.
Effect on Social Security Benefit Taxation
This is the surprise for retirees. Under IRC Section 86, tax-exempt interest is added back to your adjusted gross income when the IRS decides how much of your Social Security benefits are taxable.4Office of the Law Revision Counsel. 26 US Code 86 – Social Security and Tier 1 Railroad Retirement Benefits The dividends stay federally untaxed, but they still lift the “provisional income” figure that decides how much of your benefits are taxed.
The thresholds are fixed by statute and are not indexed for inflation:
- Single filers: provisional income between $25,000 and $34,000 makes up to 50% of benefits taxable. Above $34,000, up to 85%.
- Married filing jointly: the 50% band runs from $32,000 to $44,000; above $44,000, up to 85%.
A retiree who assumes SCMB dividends can’t push them across a threshold because the income is “tax-exempt” has the mechanics wrong. The dividends count for this calculation. The exemption on the interest itself is real, but part of it can be offset by newly taxable Social Security benefits.
Medicare IRMAA Surcharges
Medicare uses the same add-back. The Income-Related Monthly Adjustment Amount adds surcharges to Part B and Part D premiums when your modified adjusted gross income (AGI plus tax-exempt interest) crosses set thresholds. For 2026, surcharges begin above $109,000 for single filers and $218,000 for joint filers, and IRMAA looks at your tax return from two years earlier, so SCMB dividends earned in 2024 flow into your 2026 premiums.
The dollars matter. Monthly Part B surcharges for 2026 run roughly from $81 to $487 per person on top of the standard premium, and Part D surcharges from about $15 to $91. For a married couple both on Medicare at the highest tier, the added annual cost can exceed $13,000. That number belongs in any yield comparison between SCMB and a taxable alternative.
Alternative Minimum Tax and Private Activity Bonds
A portion of SCMB’s holdings may be classified as private activity bonds, meaning more than 10% of the bond’s proceeds benefit a private business rather than the general public.5Office of the Law Revision Counsel. 26 US Code 141 – Private Activity Bond; Qualified Bond Interest on “specified” private activity bonds is a tax preference item under IRC Section 57 and gets added back when calculating the Alternative Minimum Tax. Certain housing bonds, veterans’ mortgage bonds, and bonds issued by 501(c)(3) organizations are excluded from this treatment.6Office of the Law Revision Counsel. 26 USC 57 – Items of Tax Preference
For 2026, AMT exemptions are $90,100 for single filers and $140,200 for married joint filers, phasing out at $500,000 and $1,000,000 respectively.7Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Schwab publishes the percentage of SCMB’s income attributable to private activity bonds in its annual tax supplement. For most investors that percentage is small and the AMT impact minimal. If you already carry other preference items and sit near the exemption, check.
Capital Gains When You Sell Shares
The exemption is on interest, not on price appreciation. If you sell SCMB shares for more than you paid, the profit is a capital gain taxed like any other investment sale. Long-term rates for 2026, on shares held more than a year, are 0%, 15%, or 20% depending on taxable income.8Internal Revenue Service. Topic No. 409, Capital Gains and Losses Shares held a year or less are taxed at your ordinary rate.
The 3.8% Net Investment Income Tax can also apply if your MAGI exceeds $200,000 (single) or $250,000 (joint). Tax-exempt muni bond interest is excluded from net investment income, but capital gains are not.9Internal Revenue Service. Topic No. 559, Net Investment Income Tax Selling at a profit can therefore be taxed at a combined federal rate up to 23.8%. If you reinvest dividends, keep track of the separate tax lots at different cost bases.
Margin Interest Is Not Deductible
If you buy SCMB with margin or any other borrowed money, the interest on that debt is not deductible. IRC Section 265 disallows deductions for interest on debt incurred to purchase or carry investments producing tax-exempt income.10Office of the Law Revision Counsel. 26 US Code 265 – Expenses and Interest Relating to Tax-Exempt Income The rule applies to individual investors, and the IRS does not require a direct tracing between the loan and the purchase. Carry margin debt and hold tax-exempt funds, and the IRS may allocate a portion of your margin interest as nondeductible.
How SCMB Income Shows Up at Filing Time
Because SCMB is an ETF, its tax-exempt income reaches you as exempt-interest dividends, not as bond interest. Your broker reports them on Form 1099-DIV Box 12, not on Form 1099-INT.2Internal Revenue Service. 1040 (2025) Instructions – Line 2a Put the Box 12 total on Line 2a of Form 1040. If part of the income came from private activity bonds, that amount is in Box 13 and belongs on Form 6251 for AMT.
On the state return, if your state exempts home-state muni interest, subtract the qualifying portion of the dividends on the appropriate line using the fund’s state-by-state allocation. Match the totals on your return to what the broker reported; the IRS receives the same forms and flags mismatches automatically.