Tax-Equivalent Yield: Comparing Municipal vs Taxable Bonds
When comparing municipal bonds to taxable alternatives, the stated yields can be misleading. A 3.5% tax-exempt muni and a 5% corporate bond aren’t directly comparable — one is taxed, the other isn’t. Tax-equivalent yield (TEY) solves this problem by converting tax-exempt municipal bond yields into their taxable equivalents, enabling apples-to-apples comparison.
Whether you’re deciding between a California GO muni and a corporate bond, or comparing an in-state muni to a Treasury, understanding TEY helps you make the right fixed income allocation decision for your tax situation.
What Is Tax-Equivalent Yield?
Tax-equivalent yield is the yield a taxable bond must offer to provide the same after-tax return as a tax-exempt municipal bond. It answers a simple question: “How much would a taxable bond need to yield to match the after-tax income from this tax-exempt muni?”
TEY converts tax-exempt yields to taxable equivalents. A 3.5% tax-exempt muni for an investor in the 37% federal bracket has a TEY of 5.56% — meaning a taxable bond would need to yield at least 5.56% to match the muni’s after-tax return.
The higher your marginal tax bracket, the more valuable tax-exempt income becomes. For investors in top brackets, municipal bonds often provide superior after-tax returns compared to higher-yielding taxable alternatives.
The Tax-Equivalent Yield Formula
The TEY formula is straightforward:
Where:
- Tax-Exempt Yield — the municipal bond’s yield to maturity (YTM), not the coupon rate
- Marginal Tax Rate — your highest tax bracket rate, including federal, state, and local taxes where applicable
An investor in the 37% federal bracket is considering a tax-exempt municipal bond yielding 3.50% YTM.
TEY = 3.50% / (1 – 0.37) = 3.50% / 0.63 = 5.56%
A taxable bond would need to yield at least 5.56% to match the muni’s after-tax return.
Which Tax Rate Should You Use?
Choosing the correct tax rate is the most critical — and most commonly misunderstood — part of the TEY calculation.
Marginal vs. Average Tax Rate
Always use your marginal tax rate, not your average or effective tax rate. Your marginal rate is the tax on the next dollar of income — which is exactly what bond interest represents. Using your average rate will understate the true TEY.
Federal Rate
Your federal marginal tax bracket depends on your taxable income and filing status. The top federal bracket is 37% for high earners. Additionally, the Net Investment Income Tax (NIIT) adds 3.8% to investment income for taxpayers above certain thresholds ($200,000 single / $250,000 married filing jointly). Municipal bond interest is exempt from NIIT, so high-income investors effectively face a 40.8% combined federal rate when comparing munis to taxable bonds.
State and Local Rates
For in-state municipal bonds, add your state (and local, if applicable) marginal tax rate. Most states exempt interest from bonds issued within their state. For out-of-state munis, the state exemption typically does not apply — the out-of-state muni interest is usually taxable at the state level.
Out-of-state munis complicate the comparison. Since they’re federally exempt but often state-taxable, while Treasuries are federally taxable but state-exempt, you can’t simply apply the TEY formula. Compare after-tax yields directly: calculate the after-tax income from each bond given your specific tax situation.
Combined Tax Rate Calculation
For in-state municipal bonds compared to corporate bonds, calculate your combined marginal tax rate:
If you itemize deductions and benefit from the state/local tax (SALT) deduction, the calculation is slightly different because state taxes paid reduce federal taxable income:
A California resident in the 37% federal bracket with a 9.3% California state rate:
Simplified (no SALT benefit): 37% + 9.3% = 46.3%
With SALT benefit: 37% + 9.3% × (1 – 0.37) = 37% + 5.86% = 42.86%
Most high earners hit the SALT cap and should use the simplified method.
The state and local tax (SALT) deduction is capped, limiting the benefit of state tax deductibility. Check current IRS guidance for applicable limits, as these have changed over time and may change again.
When Municipal Bonds Make Sense
TEY tells you whether a muni’s tax-exempt yield justifies choosing it over a taxable alternative. The decision rule is simple: if the TEY exceeds the taxable bond’s yield, the muni wins.
Breakeven Tax Rate
You can also work backward to find the breakeven tax rate — the minimum marginal rate at which the muni becomes attractive:
Compare a 3.50% AA-rated municipal bond to a 5.00% AA-rated corporate bond:
Breakeven Rate = 1 – (3.50% / 5.00%) = 1 – 0.70 = 30%
Any investor with a marginal tax rate above 30% would prefer the muni. At the 37% federal bracket, the muni is clearly superior even before considering state taxes.
High-Yield Municipal Bonds
High-yield municipal bonds (rated BB+ or lower) offer higher stated yields than investment-grade munis, translating to even higher tax-equivalent yields. However, the enhanced TEY comes with meaningful credit risk.
While the TEY calculation works identically, investors must weigh the tax benefit against the possibility of principal loss. Notable municipal defaults — including Detroit (2013) and Puerto Rico (2015-2022) — demonstrate that munis are not risk-free. Higher TEY means little if the issuer defaults.
Compare high-yield munis to high-yield corporates of similar credit quality, not to investment-grade bonds. The appropriate comparison is risk-adjusted, not just yield-adjusted.
How to Calculate Tax-Equivalent Yield
Here’s a complete example incorporating federal, state, and NIIT considerations:
Bond: California State GO municipal bond, 3.75% YTM, AA rating
Investor: California resident, $500,000 income (single filer)
Tax situation:
- Federal marginal rate: 37%
- NIIT: 3.8% (above threshold)
- California state rate: 11.3% (top bracket for income above ~$446K)
- SALT benefit: exhausted (use simplified combined rate)
Combined rate: 37% + 3.8% + 11.3% = 52.1%
TEY = 3.75% / (1 – 0.521) = 3.75% / 0.479 = 7.83%
A taxable corporate bond would need to yield 7.83% to match this California muni’s after-tax return. For an AA-rated credit, this is an extremely high hurdle — the muni is likely the better choice.
Municipal Bonds vs Taxable Bonds
When comparing munis to taxable alternatives, recognize that “taxable bonds” is not a monolithic category. Treasuries and corporates have different state tax treatment.
Municipal Bonds
- Interest exempt from federal income tax
- In-state bonds often exempt from state/local tax
- Lower stated yields vs. taxable bonds
- Capital gains remain taxable
- Best in taxable brokerage accounts
Corporate Bonds
- Interest fully taxable at federal level
- Interest fully taxable at state/local level
- Higher stated yields vs. munis
- Wide range of credit qualities
- Better suited for tax-advantaged accounts
Treasury Securities
- Interest taxable at federal level
- Interest exempt from state/local tax
- Yields typically between munis and corporates
- No credit risk (full faith and credit)
- Compare to munis using federal-only rate
For in-state munis: when comparing to a Treasury, use only your federal rate (both are state-exempt). When comparing to a corporate, use your full combined rate. For out-of-state munis: the simple TEY formula doesn’t apply cleanly since the muni may be state-taxable — calculate after-tax yields directly.
Limitations of Tax-Equivalent Yield
TEY is a useful comparison tool, but it has several limitations that can affect investment decisions:
AMT Exposure — Certain private activity municipal bonds are subject to the Alternative Minimum Tax (AMT). If you’re an AMT taxpayer, these bonds lose some or all of their tax exemption. Check whether a muni is AMT-free before calculating TEY.
Capital Gains Are Taxable — Only the interest income is tax-exempt. If you buy a muni at a discount and sell at a gain, or if the bond appreciates before you sell, the gain is taxable. Market discount on tax-exempt bonds can be taxed as ordinary income.
Tax Rates Change — Future tax legislation can raise or lower marginal rates, changing the attractiveness of tax-exempt income. A muni that looks attractive today may be less so if rates decrease.
Credit Risk Still Exists — Tax benefits are irrelevant if the issuer defaults. High TEY on a distressed muni is not a free lunch — it reflects meaningful credit risk.
Liquidity Differences — The municipal bond market is less liquid than the Treasury market. Wider bid-ask spreads can erode the TEY advantage when trading.
Common Mistakes
Avoid these frequent errors when calculating and applying tax-equivalent yield:
Using Average Tax Rate Instead of Marginal Rate — Your effective tax rate understates the benefit of tax-exempt income. Always use your marginal rate — the tax on the next dollar of income.
Ignoring State Tax When It Applies — For in-state munis compared to corporates, you must include state tax. Omitting it understates the TEY significantly for residents of high-tax states.
Treating Treasuries Like Corporates — Treasury interest is exempt from state tax, while corporate interest is not. When comparing an in-state muni (which is also state-exempt) to a Treasury, use only the federal rate. The TEY formula works cleanly for in-state munis versus Treasuries or corporates, but out-of-state munis require direct after-tax yield comparison.
Comparing Coupon Rates Instead of YTM — A bond trading at a discount or premium has a yield to maturity different from its coupon. Use YTM for both the muni and the taxable alternative to ensure an accurate comparison.
Ignoring AMT on Private Activity Bonds — If you’re subject to AMT, interest from certain private activity munis becomes taxable. The stated TEY overstates the benefit for these bonds.
Assuming All Munis Are Risk-Free — Credit quality varies widely. Compare munis to taxable bonds of similar credit quality, not just on yield alone.
Frequently Asked Questions
Disclaimer
This article is for educational and informational purposes only and does not constitute tax or investment advice. Tax rates, brackets, and deduction limits change periodically. Consult a qualified tax professional and financial advisor before making investment decisions based on tax considerations.
