The § 199A QBI Deduction: Thresholds, SSTB Limits, and the Wage / UBIA Test

§ 199A permits a deduction equal to the lesser of (i) 20% of qualified business income plus 20% of qualified REIT/PTP income, or (ii) 20% of (taxable income less net capital gains). Mechanics live in the § 1.199A-1 through § 1.199A-5 regulations. The deduction was scheduled to sunset 12/31/2025 under TCJA; the One Big Beautiful Bill Act (P.L. 119-21) made it permanent.

What is QBI

QBI is the net of qualified items of income, gain, deduction, and loss from any qualified trade or business effectively connected with U.S. operations and included in taxable income (§ 1.199A-3). It excludes investment items (capital gains, dividends, interest not allocable to a trade or business), reasonable compensation from an S corporation, and guaranteed payments under § 707(c)-type arrangements. SE-tax deduction, self-employed health, and qualified retirement plan deductions reduce QBI to the extent attributable to the trade or business.

The threshold mechanics

The cliff sits at the § 199A(e)(2) threshold (inflation-indexed; $383,900 MFJ / $191,950 single for 2024). Below it, the full 20% applies and the SSTB and W-2 / UBIA limitations do not. Inside the phase-in range (the next $100,000 MFJ / $50,000 single), the limitations apply on a prorated basis. Above the upper bound, the limitations apply in full.

The W-2 wages / UBIA limit

For non-SSTB businesses above the threshold, the deduction per qualified trade or business is capped at the greater of:

1. 50% of W-2 wages paid by the qualified trade or business, or
2. 25% of W-2 wages plus 2.5% of unadjusted basis immediately after acquisition (UBIA) of qualified property.

"W-2 wages" is the Box 1 / Box 5 reporting per § 1.199A-2; UBIA is original cost (no § 1016 adjustments) for property still within its MACRS recovery period (or 10 years if longer).

SSTBs

Treas. Reg. § 1.199A-5 defines specified service trades or businesses (health, law, accounting, actuarial, performing arts, consulting, athletics, financial services, brokerage, investing/investment management, trading, dealing in certain assets) and the catch-all for any business where the principal asset is the reputation or skill of one or more employees or owners. Above the upper threshold, an SSTB receives no § 199A deduction.

Aggregation and the rental safe harbor

Treas. Reg. § 1.199A-4 permits aggregation of commonly controlled qualified trades or businesses to combine W-2 wages and UBIA across the group, preserving the deduction where one entity is wage-rich and another property-rich. Rental real estate qualifies as a § 162 trade or business under the facts-and-circumstances test or the Rev. Proc. 2019-38 safe harbor (250 hours of rental services, separate books, contemporaneous records).