Why a big business-loss year no longer erases your other income

You ran your S-corp at a real loss this year, say $900,000 of deductions flowing through to your personal return. Common sense says a loss that size should wipe out your other income and maybe generate a refund. Common sense is now wrong, and as of this year it is more wrong than it used to be.

The reason is a rule called the excess business loss limitation. It caps how much of a business loss you can use against your non-business income in a single year. Two things just changed, and both cut against you. The rule was scheduled to expire, and the new law made it permanent going forward. And separately, the way the cap is adjusted for inflation changed starting in 2026, which pulls it lower than the normal math would.

What the rule actually does

The limitation is the last hurdle your loss has to clear, not the first. Before you reach it, your loss already runs a gauntlet: your basis in the business, the at-risk rules, and the passive activity rules. Only the loss that survives all three gets tested here.

The test is simple to state. Add up your business deductions, subtract your business income, then subtract the threshold. Whatever is left over is your excess business loss, and it is disallowed this year.

The part most owners get wrong is what counts as income for this test. Only business income raises the cap. Your spouse's salary does not. Your portfolio dividends do not. A stock sale does not. So the large W-2 or the big capital gain you were counting on to soak up the loss does not help here.

One more thing for S-corp owners: this test applies at your level as the shareholder, not at the company level. Your other business income and activities are part of the same calculation.

The disallowed piece is not gone. It carries forward as a net operating loss you can use in future years. But future use is capped at 80% of that year's income, so you cannot fully recover it in one shot, and you have lost the use of that money in the meantime. At a 37% rate, the extra $114,000 trapped in 2026 is roughly $42,000 of tax benefit pushed out of this year.

Why the cap dropped in 2026

This cap is still adjusted for inflation, but the new law changed the base year used for that adjustment starting in 2026. The practical effect is a lower cap than the normal inflation math would have produced. For a joint filer it fell from $626,000 in 2025 to $512,000 in 2026, even as prices kept climbing.

Where it goes wrong

• Assuming a salary or a stock sale absorbs the loss. Only business income counts. Non-business income sits outside the cap.
• Maxing depreciation on autopilot. A giant first-year bonus depreciation deduction can push more of your loss over the cap and into a carryforward. Sometimes a smaller, smoothed deduction gives a better cash result.
• Forgetting the QBI hit. A big loss year produces negative qualified business income, so your §199A deduction is generally zero and the negative amount follows you into next year.
• Assuming your state follows along. Many states decouple from this rule, so a loss trapped on your federal return may behave differently on your state return.

What to model before year-end

• Project your business income and loss for the year. Is the loss large enough to cross the threshold at all?
• Could you time business income, like a gain on selling business property, into the same year? Business gains raise the cap dollar for dollar.
• Should you smooth depreciation instead of front-loading it, so more of the loss stays usable now?
• Run this before your September 15 estimated payment, not after. A miscalculation there costs you interest.

If you are heading into a loss year, the Calibration Plan models your loss against the current threshold and the multi-year carryforward drag before the estimated-payment clock runs out. Start yours at start.gnomontax.com.