Tax loss deduction rules determine whether an individual taxpayer can actually use a loss from a partnership, S corporation, or other flow-through entity on a personal tax return. Many business owners assume that any loss flowing through to their Schedule K-1 is automatically deductible, but the IRS imposes a series of tests that must be satisfied first. Understanding these hurdles is essential for anyone involved in pass-through businesses, real estate partnerships, or startup ventures that generate early-year losses.
The Tax Cuts and Jobs Act of 2017, effective for tax years beginning in 2018, made deducting losses on individual returns significantly more difficult by adding a fourth limitation on top of the three that already existed. Before 2018, individuals had to clear three hurdles, basis limitations, at-risk limitations, and passive activity loss rules, before claiming a tax loss deduction. Today, a fourth test called the excess business loss limitation applies even after a loss passes the first three.
This article answers one central question: when can you actually deduct a flow-through business loss on your individual return? The answer depends on clearing all four tests in sequence, and a loss that fails any one of them is suspended rather than allowed. Working through each test in order is the only reliable way to know how much of a loss you can claim this year.
How the basis limitation affects your deduction
The basis limitation is the first test every flow-through loss must pass. You cannot deduct losses in excess of your tax basis in the entity. Basis represents your economic investment, and the IRS requires that you have enough of it to absorb any losses before they reach your return.
For partnerships, basis includes your share of income or loss, capital contributions, and your proportionate share of partnership liabilities. Distributions reduce basis, while additional contributions and allocated income increase it. One important distinction is that partnership basis does include a partner’s share of the entity’s liabilities, which can meaningfully increase the amount of losses a partner can deduct.
S corporation basis works differently in a critical way. A shareholder’s basis includes their share of income or loss, capital contributions, and direct loans the shareholder makes to the S corporation. Unlike partnerships, S corporation basis does not include the entity’s liabilities. This means S corporation shareholders may run into basis limitations more quickly than their partnership counterparts, especially in businesses that carry significant debt.
If your basis is reduced to zero, any excess loss is suspended and carried forward to future years when additional basis becomes available. The IRS describes these mechanics in Publication 541 on partnerships and in the S corporation guidance for Form 1120-S shareholders. Tracking basis annually, rather than reconstructing it years later, is the practice that prevents most disputes on audit.
Understanding the at-risk rules for business losses
Once a loss passes the basis limitation, it must clear the at-risk rules. These rules further restrict your allowable deduction to the amount you actually have at economic risk in the activity. The purpose is to prevent taxpayers from deducting losses financed entirely by nonrecourse borrowing where they face no real financial exposure.
For partnerships, amounts at risk include cash and property contributions plus any amounts borrowed for which the partner is personally liable. Nonrecourse financing is generally excluded from the at-risk calculation unless it qualifies as qualified nonrecourse financing secured by real property used in the activity. This exception is significant for real estate investors, as it allows certain mortgage debt to count toward the at-risk amount.
For S corporations, the at-risk amount includes contributions of cash or property and direct loans from the shareholder to the corporation. Bank loans guaranteed by the shareholder, or loans from third parties, do not increase the at-risk amount for S corporation purposes. This narrower definition catches many S corporation shareholders off guard, particularly those who personally guarantee business debts but cannot include those guarantees in their at-risk calculation.
If your loss exceeds your at-risk amount, the excess is suspended and carried forward. It becomes deductible in a future year when your at-risk amount increases, for example through additional capital contributions or direct shareholder loans. Owners of leveraged property businesses should review these rules with real estate accounting specialists before assuming guaranteed debt will support a current deduction.
Passive activity loss rules and material participation
The passive activity loss rules represent the third hurdle for any business loss from a flow-through entity. Congress enacted these rules as anti-tax-shelter provisions to ensure that passive losses can only offset passive income, not wages, portfolio income, or other non-passive earnings.
A passive activity is any trade or business in which the taxpayer does not materially participate. Material participation generally requires involvement in the business on a regular, continuous, and substantial basis. The IRS provides seven tests for material participation, the most common being participation of more than 500 hours during the tax year, as detailed in the instructions for Form 8582.
Rental real estate activities are generally classified as passive regardless of the taxpayer’s level of participation, with one important exception. Taxpayers who qualify as real estate professionals, meaning they spend more than 750 hours per year in real property trades or businesses and more than half their working time in those activities, can treat rental losses as non-passive. This exception is highly valuable for full-time real estate investors, but it requires careful documentation of hours spent.
If a loss is classified as passive, it can only offset passive income from other activities. Any excess passive loss is suspended and carried forward indefinitely. The suspended losses become fully deductible when the taxpayer disposes of the entire interest in the passive activity in a taxable transaction.
Taxpayers can also make elections to aggregate multiple business activities for both at-risk and passive activity loss purposes. Aggregation can sometimes help satisfy material participation requirements or allow losses from one activity to offset income from another related activity. The election is binding in later years, so it deserves analysis before it is filed rather than after.
The excess business loss limitation explained
Even after clearing the basis, at-risk, and passive activity hurdles, a deductible business loss may still be capped by the excess business loss limitation. This fourth test was created by the Tax Cuts and Jobs Act and applies at the individual taxpayer level across all business activities.
The excess business loss limitation caps the total net business loss an individual can deduct in a single tax year. For tax years beginning in 2026, the limit is $512,000 for married filing jointly or $256,000 for single filers, according to the IRS guidance on excess business losses. For 2025 the thresholds were higher, at $626,000 and $313,000, so the inflation-adjusted figures move from year to year and should always be checked against the current Form 461 instructions. Any business loss exceeding the applicable threshold is not permanently lost. It is treated as part of the taxpayer’s net operating loss carryforward and is subject to the 80 percent of taxable income limitation that applies to NOLs.
The calculation aggregates all of a taxpayer’s business income and losses, including self-employment income, partnership and S corporation income or losses that have already passed the first three tests, and business-related capital gains and losses. The IRS explains these mechanics and the current threshold amounts on its excess business losses page. If the net result is a loss exceeding the annual threshold, the excess becomes an NOL carryforward.
The CARES Act temporarily suspended the excess business loss limitation for tax years 2020 and 2021, but it was reinstated for 2022 and subsequent years. The Inflation Reduction Act of 2022 originally extended the provision through 2028, and the One Big Beautiful Bill Act enacted in 2025 went further by making the limitation permanent and adjusting how the inflation indexing is calculated. Taxpayers should plan for this limitation to remain a permanent fixture of the tax code rather than a temporary rule with a sunset date.
Strategies to maximize your business loss deductions
Understanding each limitation is the first step toward planning around them. Taxpayers who anticipate losses from flow-through entities should consider several proactive strategies, ideally with input from a tax advisory team before the year closes.
Increasing basis before year-end through capital contributions or shareholder loans, in the case of S corporations, can unlock suspended losses. For partnership interests, reviewing your share of entity liabilities and understanding how recourse versus nonrecourse debt affects your basis can reveal additional deduction capacity. Both moves must be real and documented, not paper transactions reversed shortly after year-end.
Tracking hours of material participation is critical for avoiding passive classification. Keep a contemporaneous log throughout the year rather than trying to reconstruct hours at tax time. For taxpayers with multiple business activities, evaluate whether aggregation elections could help satisfy material participation or allow more favorable netting of income and losses.
For the excess business loss limitation, planning the timing of income recognition and loss realization across tax years can help stay within the annual threshold. Taxpayers who expect large losses should also model the impact of the NOL carryforward rules, including the 80 percent of taxable income limitation, on their multi-year tax picture. Coordinating that modeling with broader accounting services keeps the loss strategy consistent with cash flow and entity structure decisions.
Consulting a tax adviser before year-end is the most effective way to work through these overlapping rules and ensure you capture every available deduction. Because the four tests apply in sequence, a single planning move can free a loss under one rule while leaving it trapped under another, which is why coordinated review matters.
Frequently Asked Questions
Can I deduct a business loss on my personal tax return?
Yes, but only if the loss clears four separate tests: basis limitation, at-risk limitation, passive activity loss rules, and the excess business loss limitation. Each test can reduce or suspend the amount you are allowed to deduct. Losses that fail any test are carried forward to future tax years rather than lost permanently.
What is the excess business loss limitation for 2026?
For tax years beginning in 2026, the excess business loss limitation caps deductible business losses at $512,000 for married filing jointly or $256,000 for single filers. The thresholds are adjusted for inflation, so the 2025 figures were higher at $626,000 and $313,000. Any net business loss exceeding the applicable threshold is converted into a net operating loss carryforward, which is subject to the 80 percent of taxable income limitation in future years.
How do passive activity loss rules affect my deduction?
Passive activity loss rules prevent you from using losses from a business in which you do not materially participate to offset non-passive income like wages or investment earnings. Passive losses can only offset passive income. Suspended passive losses carry forward and become fully deductible when you sell your entire interest in the activity.
What is the difference between basis limitations for partnerships and S corporations?
Partnership basis includes a partner’s share of entity liabilities, while S corporation basis does not. This means partners can often sustain larger tax loss deductions because their basis is increased by their share of partnership debt. S corporation shareholders can only increase basis through capital contributions and direct loans to the corporation.
Do at-risk rules apply differently to real estate investments?
Real estate benefits from an exception under the at-risk rules: qualified nonrecourse financing secured by real property counts toward your at-risk amount, even though you are not personally liable for the debt. This exception does not apply to other types of business activities, where only recourse debt and personal contributions increase your at-risk amount.
Will the excess business loss limitation expire?
No. The Inflation Reduction Act of 2022 had extended the limitation through 2028, but the One Big Beautiful Bill Act enacted in 2025 made the excess business loss limitation permanent and removed the prior sunset date. Taxpayers should plan with the assumption that this limitation is now a permanent part of the tax code, subject to annual inflation adjustments rather than expiration.
