Tax-equivalent yield converts a tax-exempt yield into the pretax yield a taxable investment would need to provide the same simplified after-tax income.
Tax-equivalent yield (TEY) is the pretax yield a fully taxable investment would need to provide the same simplified after-tax income as a tax-exempt investment. Investors most often use it to compare municipal bonds with taxable bonds in a taxable account.
This taxable-versus-exempt comparison is also described as yield equivalence. An equivalent yield is a calculated comparison, not an additional payment from the tax-exempt investment.
TEY adjusts for tax treatment, not investment risk. A municipal bond with a higher tax-equivalent yield is not necessarily preferable if its credit quality, call exposure, maturity, liquidity, or price differs from the taxable alternative.
When the bond’s interest is fully exempt from the tax represented by marginal rate (t), expressed as a decimal with (0\leq t<1):
The matching after-tax yield on a taxable bond is:
These formulas assume the stated yield is income subject to the selected tax rate and omit capital gains, losses, deductions, premiums, discounts, and transaction costs.
Assume a municipal bond is purchased at par, pays an annual coupon of 4.00%, and its interest is exempt from the tax represented by a hypothetical 35% marginal rate. Principal is repaid at par as scheduled; fees and other taxes are excluded.
Under those assumptions, a fully taxable bond would need a yield of approximately 6.15% to produce the same simplified after-tax income.
Now compare a taxable bond also purchased and repaid at par, with a 6.00% annual coupon subject to that rate:
| Bond | Quoted yield | Simplified after-tax yield |
|---|---|---|
| Tax-exempt municipal bond | 4.00% | 4.00% |
| Fully taxable bond | 6.00% | 3.90% |
The municipal bond leads by 0.10 percentage point on this tax-only comparison. That small difference can be outweighed by price, default risk, call terms, trading costs, or a change in the tax assumption.
The formula can be rearranged to find the marginal tax rate at which a tax-exempt yield equals a taxable yield:
For a 4.00% tax-exempt yield and a 6.00% taxable yield:
Above the simplified 33.33% break-even rate, the tax-exempt bond produces more after-tax income; below it, the taxable bond does. This remains a tax-only result and assumes matched risk and yield measures.
The most common TEY error is using a headline bracket that does not apply to the bond interest. The rate should reflect the incremental tax on that income.
Interest on many state and local government obligations is exempt from regular federal income tax. Some municipal interest is taxable, and interest from certain private activity bonds can be an alternative minimum tax preference item.
A state may exempt interest from in-state municipal bonds while taxing interest from out-of-state bonds. Rules vary, and local income taxes can add another layer.
If taxable interest is subject to federal and state tax while municipal interest is exempt from both, use a combined effective marginal rate that reflects how those taxes actually interact. Simply adding statutory rates can overstate the result because federal deductibility, caps, and state rules may alter the combined burden.
Net investment income tax, corporate rules, trust brackets, and state-specific adjustments can change the incremental rate. Do not use an individual’s ordinary bracket for a corporation, retirement account, trust, or tax-exempt entity.
When municipal interest is exempt federally but taxable by the state, first calculate the municipal bond’s own after-tax yield:
where (t_m) is the effective marginal tax rate that actually applies to the municipal interest. Then compare that amount with the taxable bond after all taxes applicable to taxable interest.
Assume a 4.00% out-of-state municipal yield faces a hypothetical 5% state tax but remains federally exempt:
Using 4.00% as fully exempt would overstate its after-tax yield by 0.20 percentage point.
To express the partially exempt yield on a taxable-equivalent basis:
Here (y_m) is the municipal income yield and (t_b) is the effective marginal rate on the taxable alternative’s interest. Both rates must reflect the taxes actually being modeled, rather than a mechanical sum of statutory brackets.
If the taxable alternative faces a hypothetical combined rate of 35%, the 3.80% after-tax municipal income yield requires:
A taxable income yield of about 5.8462% leaves 3.80% after the assumed tax. Treating the municipal interest as fully exempt would instead give 6.1538%, overstating the equivalent taxable yield by approximately 30.77 basis points. These are simplified income comparisons, not statements about any investor’s actual tax liability.
TEY is only as consistent as the yield input. Avoid comparing:
For callable bonds, yield to worst often provides a more conservative common measure because it considers the lowest specified yield among relevant call and maturity outcomes. It still is not a forecast or guarantee.
Even matched YTM or YTW inputs do not make the tax shortcut exact. Those yields can incorporate a redemption gain or loss as well as coupon income, with different tax treatment and timing. For a full after-tax yield calculation, model the separately taxed cash flows and solve for their discount rate. The IRS’s investment-income guidance explains why coupon interest, premium, market discount, and disposition proceeds cannot always receive one uniform adjustment.
The phrase “tax-exempt bond” generally refers to qualifying interest. Other returns can have different treatment:
| Return component | Possible treatment |
|---|---|
| Qualifying stated interest | May be exempt from regular federal income tax |
| Original issue discount on a qualifying tax-exempt bond | Generally accrues as tax-exempt interest, subject to the applicable rules |
| Market discount | Can produce taxable income on sale or redemption |
| Gain from selling above adjusted basis | Generally subject to capital-gain rules |
| Loss on sale | Subject to capital-loss and bond-specific rules |
| Private activity bond interest | May be an AMT preference item |
Read the official statement and tax disclosure for the specific security. Issuer type alone does not prove every payment is exempt.
Tax-equivalent yield focuses on income. Total return also reflects:
This is a simplified dollar calculation before investor-level tax, assuming income is not already included in ending value. Expressing it as a percentage requires a consistent invested-value denominator and appropriate treatment of external cash flows.
A bond can generate the expected tax-exempt interest and still lose market value because rates rise, credit quality weakens, liquidity deteriorates, or the market expects a call outcome different from the purchase assumption.
For a bond held to maturity, default, call, premium amortization, reinvestment, and inflation still affect realized results.
Before using TEY to choose between bonds, align:
Only after these are reasonably matched does TEY isolate the tax difference usefully.
TEY is most relevant in a taxable account where interest tax differs between investments. Inside many retirement accounts, current bond interest is already deferred or exempt at the account level. A bond’s interest exemption may therefore add no current tax benefit within the account; its yield and other investment features still need evaluation.
Account withdrawals may later be taxable under separate rules. That treatment should be modeled at the account level rather than inserted into the simple annual TEY formula.
TEY is a one-variable normalization. It does not predict default, price change, call timing, reinvestment rates, liquidity, inflation, or tax-law changes. The investor’s actual rate can also differ from the assumed marginal rate because of income changes, deductions, surtaxes, entity status, or state residence.
A security with attractive tax treatment can still be unsuitable or overpriced. Use current tax guidance and security disclosures rather than relying on an advertised TEY alone.
This page provides general U.S. financial and tax education. It is not individualized tax, legal, fixed-income, portfolio, or investment advice.