At-Risk Rules and Basis Limitations: The Tax Traps That Can Block Pass-Through Business Losses

Pass-through losses from an S-Corp or partnership flow through to your personal return on Schedule K-1. But a K-1 loss doesn't automatically translate into a deduction. Multiple limitation systems — including basis, at-risk, and passive activity loss rules — can block or defer that deduction, sometimes for years. Understanding how these work prevents surprises on your return and helps you plan around them.

Basis Limitations

In an S-Corp or partnership, your ability to deduct a loss is limited to your tax basis in the entity. Basis is essentially your economic investment in the entity, tracked on paper. It goes up when you contribute capital or the entity earns income allocated to you, and down when you take distributions or the entity has losses allocated to you.

For S-Corps: Your basis consists of stock basis (contributions plus income minus distributions) and loan basis from direct loans you personally made to the corporation. Third-party loans to the S-Corp do not increase a shareholder's basis. This is a critical distinction—if the bank loaned your S-Corp $200,000, that doesn't give you $200,000 of basis to absorb losses.

For partnerships: Basis generally includes your capital contributions plus your allocable share of partnership liabilities, including certain third-party debt. But basis and at-risk are not the same thing, and not every liability that increases basis increases the amount you are considered at-risk for. This is why partnerships are often more tax-favorable for leveraged real estate—the debt creates basis that allows more loss to flow through to partners currently.

If your K-1 shows a $60,000 loss but your basis is only $25,000, you can only deduct $25,000 this year. The remaining $35,000 is suspended until you have sufficient basis—which you build through future contributions or income allocations.

At-Risk Rules

At-risk rules under IRC §465 operate separately from and in addition to basis limitations. They restrict losses to the amount you actually have at economic risk in the activity. At-risk includes cash contributed, the basis of property you contributed, and amounts you personally borrowed for which you're personally liable. It does not include loans where the lender—or another party—has protected you against loss.

Passive Activity Loss Rules: The Third Filter

Once a loss clears both basis and at-risk limitations, it still faces the passive activity loss rules under IRC §469. Passive losses can only offset passive income—they cannot offset wages, interest, dividends, or active business income. One common material participation test is more than 500 hours, but that is not the only test. If you do not materially participate under the applicable rules, the activity is generally passive. If your only investment in the S-Corp is as a passive investor-shareholder, your losses are passive and can only be used against passive income from other sources.

These Limitations Stack—In Order

The practical point is this: a K-1 loss generally has to clear basis, at-risk, and passive activity rules before it becomes currently deductible. A suspended loss at any level carries forward until the constraint is satisfied, or until another event allows the loss to be used. For passive losses, a fully taxable disposition of the entire activity to an unrelated party may release suspended passive losses, but the exact result depends on which limitation created the suspension. If you're an investor in multiple pass-through entities and you're not tracking your basis and at-risk amounts, you may be leaving deductions on the table or taking deductions you're not entitled to. Both create problems.