Best Muni National Intermediate Mutual Funds

Municipal bond funds invest in debt securities issued by state and local governments, their agencies, and related entities. The defining feature of municipal bonds is that their interest income is exempt from federal income tax, and in many cases from state and local taxes as well. This tax advantage makes muni bond funds a cornerstone of taxable account investing for investors in higher tax brackets.

National intermediate municipal bond funds specifically invest in munis from across all 50 states with intermediate maturities (typically 3–10 years). The "national" designation means the fund diversifies across many states rather than concentrating in a single state's bonds. The intermediate duration balances yield against interest rate sensitivity.

These funds invest primarily in investment-grade municipal bonds—those rated BBB or higher by major rating agencies. The issuers include states, cities, counties, school districts, water authorities, transportation agencies, and hospitals. Default rates on investment-grade municipal bonds have historically been extremely low, making this one of the safer segments of the fixed-income market.

Vanguard dominates this category with two excellent low-cost options:

Vanguard Intermediate-Term Tax-Exempt (VWITX) — The Category Leader - 1-Year Return: +3.68% - Expense Ratio: 0.17% - Tax-Exempt Yield: 3.38% - AUM: $87.2B

VWITX is a massive $87.2B fund that has served as the go-to muni bond holding for millions of taxable-account investors. Its 3.38% tax-exempt yield is equivalent to a taxable yield of approximately 5.2–5.7% for investors in the 32–37% federal tax bracket. The 0.17% expense ratio is excellent for a muni bond fund.

Vanguard Tax-Exempt Bond (VTEBX) — The Ultra-Low-Cost Alternative - 1-Year Return: +3.43% - Expense Ratio: 0.05% - Tax-Exempt Yield: 3.09% - AUM: $34.9B

VTEBX offers even lower costs at just 0.05%, making it one of the cheapest muni bond funds available. Its slightly lower yield (3.09% vs. 3.38%) and return (+3.43% vs. +3.68%) reflect its broader index approach compared to VWITX's actively managed strategy. For cost-minimizing investors, VTEBX is compelling.

The tax-exempt status of municipal bond interest creates significant value for investors in higher tax brackets. Here's how the math works:

Tax-equivalent yield calculation: Tax-Equivalent Yield = Muni Yield ÷ (1 − Marginal Tax Rate)

For VWITX with a 3.38% yield: - At the 24% bracket: 3.38% ÷ 0.76 = 4.45% equivalent - At the 32% bracket: 3.38% ÷ 0.68 = 4.97% equivalent - At the 37% bracket: 3.38% ÷ 0.63 = 5.37% equivalent

This means a taxpayer in the 37% bracket would need a taxable bond yielding over 5.37% to match the after-tax income from VWITX. Compare this to intermediate-term bond funds like VBMFX yielding 3.16%—after taxes at 37%, that yields just 1.99%, far below the muni fund's 3.38%.

When munis make sense: Generally, investors in the 24% federal tax bracket and above benefit from municipal bonds in taxable accounts. Those in lower brackets may find that taxable bonds offer better after-tax returns. If investing in a tax-advantaged account (IRA, 401k), always use taxable bonds instead—there's no benefit to tax-exempt income in an already tax-sheltered account.

Both Vanguard funds are excellent choices, but they differ in meaningful ways:

VWITX — Active Management (0.17%) - Managed by Vanguard's experienced municipal bond team - Can select individual bonds for credit quality and relative value - Higher yield (3.38%) suggests more targeted security selection - Larger asset base ($87.2B) provides stability and liquidity - Slightly higher return (+3.68% vs. +3.43%) over the past year

VTEBX — Index Approach (0.05%) - Tracks a broad municipal bond index - Ultra-low 0.05% expense ratio—just $5 per $10,000 invested - More diversified across thousands of municipal bonds - Lower yield reflects broader, less selective approach - Ideal for investors who prioritize cost above all else

The 0.12% fee difference between the two funds is modest in absolute terms, but in the low-return world of municipal bonds, it represents roughly 3–4% of annual income. If VWITX's active management consistently adds more than 0.12% in value—which recent results suggest it does—the slightly higher fee is justified.

Municipal bond funds are a critical component of tax-efficient portfolio construction. Here's how to use them effectively:

Asset location strategy: Hold muni bond funds in taxable brokerage accounts where their tax exemption provides maximum benefit. Keep taxable bonds (like VBMFX or PIMIX) in tax-advantaged accounts like IRAs. This simple asset location decision can add meaningful after-tax value over time.

Complement to equity holdings: Pair muni bonds with tax-efficient equity index funds in your taxable account. A combination of a large blend index fund, an international stock fund, and VWITX or VTEBX creates a highly tax-efficient taxable portfolio.

Income planning in retirement: For retirees in higher tax brackets, muni bond funds provide income that doesn't increase your adjusted gross income, which can have cascading benefits: lower Medicare premiums, reduced Social Security taxation, and eligibility for certain tax credits.

State tax considerations: National muni funds hold bonds from many states. If you live in a high-tax state (California, New York, New Jersey), you may benefit from a state-specific muni fund that provides both federal and state tax exemption. However, state-specific funds sacrifice geographic diversification.

For more on building tax-efficient portfolios, see our comprehensive guide on the best mutual funds for taxable accounts.