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Municipal Bonds

AMT and Private-Activity Bonds

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AMT and Private-Activity Bonds

Some municipal bonds are classified as private-activity bonds (PABs) and generate interest income subject to the Alternative Minimum Tax. For investors subject to AMT, buying PABs can result in unexpected tax bills despite the "tax-exempt" label.

Key takeaways​

  • Private-activity bonds finance projects where a private business or individual benefits significantly, not just the public
  • Interest on PABs is tax-exempt from regular income tax, but the interest is included in Alternative Minimum Taxable Income (AMTI)
  • Investors subject to AMT pay tax on PAB interest at their AMT rate (often 26% or 28%), negating much of the tax benefit
  • High-income earners with large deductions or significant state income taxes are most likely to be subject to AMT
  • The solution is to avoid PABs (or carefully model the tax impact) and focus on non-AMT bonds

What is a private-activity bond?​

A private-activity bond is a municipal bond where a substantial portion of the proceeds directly benefits a private business or individual, not primarily the general public. The Internal Revenue Service monitors whether a bond qualifies as a PAB.

Examples of PABs:

  • Bonds financing a sports arena or stadium for a professional sports team: the team is a private entity that benefits substantially
  • Bonds financing an industrial facility leased to a manufacturing company: the company benefits directly
  • Bonds financing a parking garage or hotel for a private developer: the private owner operates and profits from it
  • Bonds financing certain housing projects where private developers benefit
  • Bonds financing charter schools: the charter school operator (a private nonprofit) is the substantial beneficiary

Examples of non-PABs (regular tax-exempt munis):

  • Bonds financing a public high school: the public school system benefits, and the public has access
  • Bonds financing a water treatment plant: all public customers benefit equally
  • Bonds financing a courthouse, fire station, or city hall: these are purely governmental
  • Bonds financing public roads and highways: the public benefits
  • Bonds financing hospitals and healthcare facilities: even if privately operated, they serve the public

The distinction is sometimes subtle. The IRS has complex rules about what percentage of the project's benefits can accrue to private parties before the bond is classified as a PAB.

The Alternative Minimum Tax primer​

The Alternative Minimum Tax (AMT) is a parallel tax system that runs alongside the regular income tax. The idea (from 1969) was to prevent high-income earners from reducing their tax bills to near-zero through deductions and tax-exempt income.

You calculate AMT by:

  1. Taking your regular taxable income
  2. Adding back certain items that are deductions under the regular tax (state and local taxes, mortgage interest over certain limits, certain other deductions)
  3. Adding AMT preferences (including PAB interest)
  4. Subtracting the AMT exemption (roughly $85,900 for married filers in 2024, phase out above certain income)
  5. Multiplying by the AMT rate (26% or 28%)
  6. Comparing to your regular tax liability
  7. Paying whichever is higher

If your AMT exceeds your regular tax, you owe AMT instead.

The issue with PABs is that the interest (which is not taxable under regular income tax rules) is added back as a preference item in the AMT calculation. So you get no tax benefit from the PAB interest at all — or you get only a partial benefit if the AMT is lower than your regular tax rate.

Who is subject to AMT?​

The AMT primarily affects:

  1. High-income earners: Those earning over $200,000 (single) or $250,000 (married) are far more likely to be subject to AMT. The higher your income, the more likely AMT will apply.

  2. Residents of high-tax states: State and local taxes (SALT) are added back in the AMT calculation. A resident of California with $300,000 income, paying 13.3% state income tax, gets back $39,900 in state taxes as an adjustment. This increases AMTI dramatically, pushing them into AMT territory.

  3. Those with large itemized deductions: Mortgage interest, charitable donations, and other deductions can be added back (with limits) in AMT calculations, increasing AMTI.

  4. Those with concentrated stock positions: Appreciated securities and incentive stock options generate tax-preference income that is included in AMT.

The AMT was never indexed for inflation, so even middle-income earners face it now. In 2024, rough estimates suggest 5-6 million taxpayers face AMT, though many are high-income.

To know if you are subject to AMT, you need to calculate (or have a tax preparer calculate) your AMT liability each year. It is not something you can eyeball; tax software is necessary.

The PAB interest surprise​

Here is where PABs create a nasty surprise: you might buy a "tax-exempt" bond thinking you will avoid federal income tax on the interest, only to discover that the interest is subject to AMT.

Example:

You are a resident of California with $400,000 income, married filing jointly. Your federal marginal tax rate is 35%, but you also face California state income tax (13.3%). You are likely subject to AMT.

You buy a municipal bond yielding 3.5%, which you believe is tax-exempt. But the broker did not clearly disclose that it is a PAB. You receive $3,500 in annual interest.

Under regular income tax rules, the $3,500 is not taxable. You pay no federal income tax on it.

But in your AMT calculation, the $3,500 PAB interest is added as a tax preference. Combined with your state taxes, concentrated deductions, or other preferences, your AMT may exceed your regular tax. You now owe 26% or 28% AMT on the PAB interest — or on a portion of it.

Your effective tax rate on the PAB interest becomes 26-28%, not 0%. The tax-exempt advantage has evaporated.

Compare this to a regular (non-AMT) muni yielding 3.4% (slightly lower yield because it is less attractive to AMT-subject investors). The 3.4% is truly tax-free for you. The regular muni is actually superior despite the lower stated yield.

How to identify PABs​

Before buying a municipal bond, ask the broker whether it is a PAB. The term should be disclosed clearly. You can also check the EMMA (Electronic Municipal Market Access) database, maintained by the Financial Industry Regulatory Authority (FINRA), where most munis are registered and details (including PAB status) are disclosed.

If you are unsure, avoid the bond. There are plenty of non-AMT munis available; there is no reason to buy a PAB if you are subject to AMT.

Deciding whether to buy a PAB (for those subject to AMT)​

If you are subject to AMT, the analysis changes:

For a regular (non-AMT) muni yielding 3.5% with 35% federal + 8% state = 43% marginal rate:

  • TEY = 3.5% ÷ (1 − 0.43) = 6.14% (assuming true tax exemption)

For a PAB yielding 3.8% (higher to compensate) with the same 43% marginal rate, but 26% AMT rate:

  • Your effective rate on PAB interest is 26% AMT (not 43%)
  • After-tax yield = 3.8% × (1 − 0.26) = 2.81%

The PAB, despite its higher coupon, has a lower after-tax yield (2.81%) than the regular muni (3.5% true tax-exempt = 3.5% after-tax). The PAB is inferior.

This is why sophisticated investors avoid PABs entirely if subject to AMT: the tax consequences eliminate the advantage.

Estimating your AMT exposure​

To know whether you face AMT, you need to run a calculation. Here is a rough heuristic:

  1. If your income is >$400,000 (married): You are likely to face AMT or be close
  2. If your income is $250,000–$400,000 and you live in a high-tax state (CA, NY, NJ, IL): You likely face AMT
  3. If your income is <$250,000: You probably do not face AMT (though you could, with large deductions or concentrated stock)
  4. If you have never filed an AMT return: You still might be subject; have a tax professional calculate it

The ONLY way to know for sure is to calculate your AMT liability (or have a CPA do so). Tax software can do this easily.

Beyond PABs: other AMT preferences​

Even if you avoid PABs, AMT can catch you through other mechanisms:

  • State and local tax deductions: These are added back in AMT (subject to limits), increasing AMTI
  • Depreciation on rental properties: Added back in AMT
  • Incentive stock options: Treated preferentially for regular tax but less so for AMT
  • Charitable donations of appreciated securities: Can create preferences

The interaction of multiple preferences is complex. A tax professional is invaluable.

Tax-aware bond selection strategy​

If you are subject to AMT:

  1. Focus exclusively on non-PAB municipal bonds
  2. Avoid bonds in sectors known for PABs (sports, industrial development, some housing)
  3. Ask brokers explicitly: "Is this a PAB?"
  4. Check the EMMA database disclosure
  5. If uncertain, skip it and buy a regular muni or taxable bond

If you are not subject to AMT:

  1. You can buy both PABs and non-PABs on a yield basis
  2. PABs may offer slightly higher yields (compensating for AMT investors' avoidance)
  3. Calculate TEY to decide whether munis (PAB or not) versus taxable bonds

Flowchart: muni selection with AMT considerations​

Next​

Private-activity bonds and the Alternative Minimum Tax are advanced nuances that catch many investors by surprise. But there is another type of municipal bond that was created specifically as an experiment to appeal to investors who do not benefit from tax exemption: Build America Bonds. In the next article, we'll explore this temporary program and the handful of BABs that remain outstanding.