Section 199A QBI Deduction Calculator: Does the Phase-In Range Cost You Real Money?

The 20% deduction that isn't always 20%

We ran $200,000 of qualified business income through the calculator at a taxable income of $428,600 (married filing jointly) — $34,000 into the phase-in range above the 2025 threshold. The headline "20% deduction" would suggest $40,000. The actual number, once the W-2 wage limitation partially phases in, comes out to $36,600 for a non-SSTB business — and meaningfully less for a specified service business (SSTB) at the same income, since SSTBs lose the deduction entirely by the top of the range, not just partially.

How the math works

Below the income threshold, everyone gets the full 20% of QBI, no restrictions. Above the phase-in ceiling, non-SSTB businesses are capped at the greater of 50% of W-2 wages paid, or 25% of W-2 wages plus 2.5% of the unadjusted basis of qualified property (UBIA) — while SSTBs get nothing at all. In between, both effects phase in gradually and proportionally, using the reduction-amount formula published in the IRS's own worked examples.

There's also a second, separate cap: the deduction can never exceed 20% of (taxable income minus net capital gain) — a limit that matters most for lower-income years with unusually large QBI relative to total income.

What this tool doesn't model: aggregation rules for taxpayers with multiple businesses (which can sometimes combine W-2 wages/UBIA across entities to your benefit), REIT dividends and PTP income (which get the 20% deduction without any of the wage/SSTB limitations at all), and state tax treatment, which often diverges from federal.

Math runs locally. Inputs never leave your browser.Source on github.

Where this estimate needs a second look

• Whether your business is an SSTB isn't always obvious.The line between a "specified service" and an ordinary business can be genuinely ambiguous for hybrid businesses — a consulting-adjacent tech company, for instance. Get a professional opinion if this classification meaningfully changes your outcome.
• You have multiple pass-through businesses.Aggregation rules can let you combine W-2 wages and UBIA across commonly-controlled businesses, potentially increasing your deduction — this tool models a single business only.
• Your S-Corp reasonable salary interacts with this deduction.QBI excludes reasonable compensation paid to an S-Corp owner — a higher salary (see the S-Corp Election calculator) reduces QBI itself, a real interaction between two of this site's tax tools worth modeling together.
• You hold REIT dividends or PTP income.These get the 20% deduction through an entirely separate calculation, without the SSTB or wage limitations that apply to QBI from an active trade or business.

What to actually do with this number

1. Confirm your business's SSTB status with a tax professional if it's not clearly one or the other.
2. If you're near the phase-in range and run an S-Corp, model the tradeoff between a higher reasonable salary (which reduces QBI but may reduce SE/payroll tax elsewhere) and a lower one (which preserves more QBI).
3. If you have multiple businesses, ask your tax preparer about aggregation — it can meaningfully change the W-2/UBIA-limited amount.
4. Track W-2 wages and UBIA precisely if you're anywhere near the phase-in range — small changes there have real dollar impact once you're in it.
5. Re-run this every year — the thresholds are inflation-indexed and change annually.