A Specified Service Trade or Business (SSTB) is a category of professional service businesses defined by tax law that face limitations on certain tax deductions, particularly the Section 199A qualified business income deduction.

SSTBs include fields like healthcare, law, accounting, consulting, financial services, and businesses where the principal asset is the reputation or skill of employees. If your business falls into this category and your income exceeds certain thresholds, you may not qualify for the full 20% business income deduction that other business owners enjoy.

This isn't about punishment—it's the tax code's way of distinguishing between businesses that rely primarily on personal expertise versus those with significant capital investments. Understanding whether your business is an SSTB helps you plan your tax strategy and set realistic expectations for your effective tax rate.