Specified service trade or business
Law, health, consulting and similar fields. Above the Section 199A income threshold, their QBI deduction phases out.
An SSTB, or specified service trade or business, is any business in a field named in Section 199A(d)(2). Health and law are on the list. So are accounting, actuarial science, performing arts, consulting, athletics, financial services, brokerage services, investing and investment management, and trading. Dealing in securities, partnership interests or commodities counts as well. The catch-all at the end takes in any business whose main asset is the reputation or skill of its employees or owners.
Engineers and architects show up on the related Section 1202 list. This one carves them out.
Under the threshold, being an SSTB changes nothing. For 2026, Rev. Proc. 2025-32 puts the threshold at $201,750 of taxable income, $403,500 on a joint return. Go over and the deduction shrinks across a $75,000 range ($150,000 joint). By $276,750 single or $553,500 joint, an SSTB's QBI deduction is gone.
The StructureCost calculator has a checkbox for it. Tick it when your business is on the list and your income is close to the threshold or past it.