Your client clears the passive activity hurdle. Material participation is documented, the study is engineering-based, and the K-1 shows a $900,000 non-passive loss. Then §461(l) caps the deduction at $512,000 and converts the rest into a carryforward that can only ever shelter 80 cents on the dollar. Most clients have never heard of the provision until the return is in draft, and for 2026 the ceiling is lower than it was in 2025.
Key takeaways
- IRC §461(l) limits the aggregate net business loss a non-corporate taxpayer may deduct, and it applies after §469 has already been cleared.
- 2026 thresholds: $256,000 single and married filing separately, $512,000 married filing jointly.
- Those figures reset downward from 2025's $313,000 / $626,000. OBBBA made the limitation permanent and changed the indexing base, so joint filers have $114,000 less headroom than last year.
- Disallowed amounts become an NOL carryforward, and post-2017 NOLs offset only 80% of future taxable income, so a deferred dollar is worth materially less than a deducted one.
- An unmodeled study on a large property produces a headline number the client will never fully use. Model the limitation before the engagement, not at the return.
What §461(l) Actually Limits
Sum the taxpayer's trade or business deductions, sum the trade or business gross income and gains, and if deductions exceed income by more than the threshold, the excess is an excess business loss, disallowed for the year and carried forward as a net operating loss.
Three points practitioners misstate. It is an aggregate test, not a per-activity test, so all of the taxpayer's businesses net against one another first, which is why the same $900,000 loss produces very different answers for two clients with identical real estate. It applies after §469, in the ordering basis, at-risk, passive activity, then excess business loss, so a loss that is still passive never reaches §461(l); everything in our discussion of the passive activity loss rules happens first. And it applies at the individual level, so partnerships and S corporations compute nothing here.
The 2026 Thresholds, and Why They Went Down
OBBBA made §461(l) permanent, removing the sunset practitioners planned around. It also changed the indexing base, and the 2026 effect is a reduction.
| Filing status | 2025 threshold | 2026 threshold | Change |
|---|---|---|---|
| Single, married filing separately | $313,000 | $256,000 | ($57,000) |
| Married filing jointly | $626,000 | $512,000 | ($114,000) |
Read that as a planning fact. A joint filer who ran a large study in 2025 and modeled a second acquisition on the same assumptions is now $114,000 short, moving roughly $42,000 of tax at a 37% rate into a carryforward. The reset belongs in front of clients in the first quarter.
A Worked Example: A $900,000 Loss, Married Filing Jointly
Example: married joint filers, 2026 One spouse operates a consulting S corporation. The other materially participates in a short-term rental portfolio where a cost segregation study, paired with permanent 100% bonus depreciation, produced a large non-passive loss.
| Item | Amount |
|---|---|
| Non-passive loss from the real estate activity | ($900,000) |
| Trade or business income from the consulting S corporation | $260,000 |
| Aggregate net business loss | ($640,000) |
| §461(l) threshold, MFJ 2026 | $512,000 |
| Excess business loss disallowed | ($128,000) |
| Business loss deductible in 2026 | ($512,000) |
The $128,000 does not disappear. It becomes a net operating loss carried to 2027, where it can offset no more than 80% of that year's taxable income, so the client needs $160,000 of 2027 taxable income to absorb it in one year.
Notice the sensitivity. Strip out the consulting income and the disallowed amount jumps to $388,000; add a second profitable practice and it may drop to zero. The limitation is a function of the whole return, which is why it cannot be evaluated from the study alone. Your result depends on the client's full business income picture and filing status.
Why a Deferred Dollar Is Worth Less Than a Deducted Dollar
Practitioners reassure clients that nothing is lost. That is not quite true, and the difference is measurable.
Take the $128,000 above. Deducted in 2026 at a 37% marginal rate it is worth $47,360 today. Absorbed instead in 2027, about $43,900 discounted at 8%. Stretched across 2027 through 2029 by the 80% cap and modest income, roughly $40,700.
A haircut of 7% to 14%, before three further risks: the marginal rate could fall, state conformity to the federal NOL rules varies, and a client who sells the property may wait years to use the carryforward.
Six Planning Responses, in the Order to Consider Them
1. Model before you engage. Run projected aggregate business income against the threshold before the study is ordered. It takes an hour and changes the recommendation more often than anything else on this list.
2. Elect out of bonus for a class. Electing out for 5-year property while keeping bonus on 15-year, or the reverse, is a coarse but effective dial. Those assets recover under regular MACRS, spreading the deduction into later years by design rather than by disallowance, and avoiding the 80% NOL haircut.
3. Use the transition election where it is still live. For property placed in service in the taxpayer's first tax year ending after January 19, 2025, a reduced first-year rate of 40% or 60% may be elected instead of 100%. For calendar-year taxpayers that is the 2025 return, so it is a lever for extended 2025 filings and fiscal-year clients, not a 2026 placement.
4. Sequence §179 ahead of bonus. §179 is limited to business taxable income and cannot create a loss, so it does not feed an excess business loss, and disallowed amounts carry forward free of the 80% cap. For 2026 the cap is $2,560,000, phasing out from $4,090,000, and it reaches roofs, HVAC, and fire and security systems on nonresidential property. See our comparison of §179 and bonus depreciation.
5. Time the study across two tax years. A look-back study delivers its catch-up through the §481(a) adjustment in a single year of change, and choosing which year is one of the few free levers available.
6. Spread acquisitions. Two closings in two years produce two thresholds. And because §461(l) reaches only non-corporate taxpayers, entity choice matters at the margins.
Why an Unmodeled Study Can Backfire on the Client
This is a client-relationship problem before it is a tax problem.
A provider quotes a $1.4M first-year deduction on a large property. The client hears $1.4M, mentally spends the savings, and signs. At filing, §461(l) allows $512,000, the balance becomes a carryforward, and the actual first-year cash benefit is a fraction of what the proposal implied. Nobody lied. Nobody modeled, either.
The disciplined version is unglamorous: project aggregate business income, apply the threshold, and show two numbers side by side, the deduction generated and the deduction usable. Sometimes the answer is to proceed at full bonus because a known event absorbs the carryforward next year; sometimes to elect out on a class; occasionally to wait a year. All three beat the conversation that starts in March. See our guide for CPAs and the current state of bonus depreciation for 2026.
Frequently Asked Questions
Does the limitation apply to passive losses?
No. §469 suspends them first, and only losses already allowed as non-passive enter the computation. A limited partner with a suspended K-1 loss has no §461(l) issue on it at all, a common point of confusion on syndicated deals.
Is the disallowed amount lost permanently?
No. It converts to a net operating loss carried forward indefinitely. The constraint is the 80% limitation on post-2017 NOLs, so absorption may take more than one year and the deduction loses time value along the way.
How does this interact with 100% bonus depreciation?
Directly. Permanent 100% bonus under §168(k) makes it far easier to generate a loss large enough to breach the threshold, which is why the limitation matters more now than during the phase-down years.
A Cost Seg Partner Your Firm Can Stand Behind
Precision Cost Segregation works alongside CPA firms, not around them. We deliver the engineering, the asset detail schedule, the §481(a) computation, and the Form 3115 workpapers your team needs, in a format that drops straight into your fixed asset system. Your client relationship stays yours.
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This article is provided by Precision Cost Segregation for general educational purposes and does not constitute tax, legal, or accounting advice. Tax outcomes depend on your specific facts, your tax rate, your passive activity position, and your entity structure. Figures shown are illustrative. Consult your CPA or tax advisor before acting, and engage a qualified professional to perform any cost segregation study. Information is current as of publication.
This article is general information, not tax or legal advice. Depreciation outcomes depend on your facts, elections, and current law — consult your CPA before acting. © 2026 Precision Cost Segregation.