The QBI Deduction Phaseout: Why Earning One More Dollar Can Cost You $10,000

The 20% Qualified Business Income (QBI) deduction is the centerpiece of the 2017 TCJA for self-employed and small-business owners. It looks simple: take 20% of your business income off your taxable income. But for "specified service trades or businesses" (SSTBs) — consultants, lawyers, doctors, accountants, financial advisors — the deduction phases out completely above certain income thresholds, in a way that's so abrupt that earning $1,000 of additional income can cost $10,000+ in taxes.

This article explains the phaseout mechanics, who's an SSTB, and how to plan around it.

The basics: who gets QBI

QBI is a 20% deduction on income from pass-through businesses: sole proprietorships (Schedule C), partnerships (K-1), S-corporations (K-1), and most LLCs. It's NOT available on W-2 wages or C-corporation distributions.

For 2025, the phaseout begins at:

• $241,950 taxable income for single filers (was $232,000 in 2024)
• $483,900 taxable income for married filing jointly (was $464,200)

Below those thresholds, every pass-through business gets the full 20% deduction with no complications. Above them, two things happen depending on your business type:

1. For "specified service trades or businesses" (SSTBs), the deduction phases out completely over a $50,000 single / $100,000 married range.
2. For non-SSTBs (most other businesses), the deduction starts being limited by the W-2 wages your business pays + qualified property basis.

The first one is the cliff that makes earning more income actively costly.

What's an SSTB?

The IRS lists specific service businesses where the deduction phases out. The list includes:

• Health — doctors, dentists, veterinarians, therapists, pharmacists
• Law — attorneys
• Accounting — CPAs, bookkeepers, enrolled agents
• Actuarial science
• Performing arts — actors, musicians (NOT broadcasters or producers)
• Consulting — broadly defined; includes management consulting, IT consulting, marketing consulting, etc.
• Athletics
• Financial services — financial advisors, wealth managers
• Brokerage services — securities brokers, real estate brokers (only some)
• Investing and investment management
• Trading or dealing in securities
• Any business where the principal asset is the reputation or skill of one or more employees / owners — the catch-all that pulls in many "personal brand" businesses (influencers, coaches, etc.)

Notably not SSTB: software engineering, manufacturing, real estate (with some exceptions), retail, restaurants, most trades, architecture, engineering. Architecture and engineering were originally on the SSTB list but lobbied successfully to be removed.

The phaseout math, exactly

For an SSTB, the QBI deduction is reduced linearly across the phaseout range. For 2025:

• Single filer: deduction starts phasing at $241,950 taxable income, fully gone at $291,950 (a $50,000 range).
• Married filing jointly: deduction starts phasing at $483,900, fully gone at $583,900 ($100,000 range).

The reduction is proportional to how far you are into the phaseout range. At $266,950 taxable income (halfway through for single), you get half the QBI deduction. At $291,950, zero.

The "cliff effect" example

Suppose you're a single consultant with $250,000 of taxable income, all from your consulting LLC. You're $8,050 into the phaseout. Your QBI is reduced by 8,050/50,000 = 16.1%. So instead of getting the full 20% × $250,000 = $50,000 deduction, you get $50,000 × (1 - 0.161) = $41,950.

Now imagine you do one extra project that bumps your taxable income to $260,000 (an extra $10,000 earned). Your QBI reduction grows to 18,050/50,000 = 36.1%. New QBI deduction: 20% × $260,000 × (1 - 0.361) = $33,228. So you earned an extra $10,000, but your QBI deduction shrank by $8,722. Combined with regular tax on the new income, you keep maybe $4,000 of the $10,000 you earned. Your effective marginal rate on that incremental dollar is ~60%.

Planning around the phaseout

1. Increase pre-tax retirement contributions

Pre-tax retirement contributions reduce taxable income, which is what QBI uses for the phaseout. A $23,500 401(k) contribution moves you $23,500 down on the phaseout scale. For SSTB owners hovering above the threshold, this can be the difference between losing 50% of QBI and keeping the full deduction.

A defined benefit plan can shelter $100k-$300k+ for older high-earning SSTBs and reset the QBI math entirely.

2. Defer income across years

For solo consultants, billing on December 30 vs. January 5 can move income across tax years. If one year you'd be deep in the phaseout and next year you'd be below, slide the income downward. (This works for cash-basis businesses, which most solos are.)

3. Accelerate deductions

Section 179 (full expensing of equipment), bonus depreciation on real estate, charitable bunching — all reduce taxable income and reset the QBI calculation. If you were going to buy $30,000 of equipment in January 2026, buy it in December 2025 to potentially preserve QBI on 2025 income.

4. The S-Corp / W-2 wage trick (limited)

For non-SSTB businesses above the threshold, the QBI deduction is capped at the greater of (a) 50% of W-2 wages paid by the business, or (b) 25% of W-2 wages plus 2.5% of qualified property basis. So for a non-SSTB, paying W-2 wages (including to yourself via S-Corp) can increase the QBI deduction. For an SSTB above the threshold, this doesn't help — once SSTB phaseout completes, no QBI regardless of wages.

5. C-Corp election (rare, but real)

C-Corp tax rate is a flat 21% — sometimes lower than what you'd pay personally, especially if QBI is gone and your marginal rate is 32-37%. For high-earning SSTB founders who don't need to take all profits as personal income, the C-Corp can be cheaper if you can leave money in the business. Real estate, professional practices where the owner can drive a salary plus retain earnings in the company. This is a once-a-decade decision and requires real planning — talk to a CPA.

Practical: what should an SSTB owner do?

For a single SSTB owner near the threshold:

• Below $241,950 taxable income: full QBI. No urgency. Just take it.
• $241,950 - $291,950: planning matters. Max retirement contributions; defer or accelerate income across years; consider charitable bunching.
• Above $291,950: QBI is gone. Focus shifts to entity choice (C-Corp consideration), defined benefit plans for old-age sheltering, and standard high-income optimizations (NIIT awareness, donor-advised funds).

The bottom line

For SSTB owners, the QBI phaseout is the most important income threshold of your tax year. Crossing it without planning can cost more than $10,000 from a single project. The fix is mostly retirement contribution math: push enough income below the phaseout via 401(k) / defined benefit / charitable contributions to land below $241,950 (single) or $483,900 (married joint) on the taxable income line.

Run your own numbers in the full optimizer — it factors QBI in the calculation. If you're near the threshold and it shows you above, the recommendations card will surface retirement contributions and deferred-comp strategies that pull you back below.