The Qualified Business Income deduction is a 20 percent deduction for qualifying pass-through business income, but it is limited for high earners through a combination of income thresholds, a wage and capital test, and special rules for certain professions. These limits determine whether a taxpayer takes the full statutory 20 percent deduction, a reduced amount, or none at all.
How the phase-out works
Phase-out begins once taxable income exceeds statutory threshold ranges that are adjusted for inflation. For taxpayers whose income falls below the lower threshold, the deduction is generally available without the additional limits. Once income enters the phase-in range, the deduction is gradually reduced through application of the wage and qualified property limitation, which compares the tentative 20 percent deduction to a cap equal to the greater of 50 percent of W-2 wages paid by the business or 25 percent of W-2 wages plus 2.5 percent of the unadjusted basis of qualified property. The Internal Revenue Service explains these calculation mechanics and the annual adjustment of thresholds in its published guidance Internal Revenue Service.
Specified service trades or businesses such as health, law, consulting and other professions face an additional constraint. For those service businesses, the deduction phases out more rapidly; once taxable income exceeds the upper end of the phase-in range the deduction for income attributable to the specified service business is disallowed. The Joint Committee on Taxation has summarized how the combination of income thresholds and the SSTB carve-out creates graduated access to the deduction Joint Committee on Taxation.
Causes, consequences, and practical context
The design reflects a policy trade-off: Congress intended to provide relief to small and mid-sized pass-through businesses while limiting benefits for high-income taxpayers and certain professional service providers. Consequences include higher effective marginal tax rates for affected owners, increased tax planning activity such as income timing, entity structuring, and payroll adjustments, and varied state-level outcomes because many states do not conform to the federal provision. Small business owners in service-heavy local economies, such as medical or legal practices, and high earners in high-tax regions may feel the largest practical impact. Understanding the specific application requires careful attention to filing status, taxable income, wages paid by the business, and the basis of qualifying property, as detailed in official IRS guidance.