Qualified Business Income (QBI) Deduction

Section 199A deduction for pass-through business income (20% deduction)

How it works

The QBI deduction allows eligible taxpayers to deduct up to 20% of qualified business income from pass-through entities (sole proprietorships, partnerships, S-corps). This is a below-the-line deduction that reduces taxable income after standard/itemized deductions. For high-income taxpayers, the deduction phases out linearly over a $100,000 (MFJ) or $50,000 (all other filers) income range. A manual QBI entry from a prior-year tax return always takes precedence over the auto-calculated amount.

  1. 1. Identify Qualifying Income

    Determine which income types qualify for the QBI deduction

    Qualifying Income Types:
- Schedule C (Business Income)
- Schedule E (Rental/Royalty Income)
- Schedule F (Farm Income)
- K-1 (Partnership/S-Corp Income)

Not Qualifying:
- W-2 wages, interest, dividends, capital gains

Only positive income qualifies; business losses do not generate a deduction.
    Example: Schedule C income $100k + K-1 income $50k = $150k qualifying business income

  2. 2. Calculate Base QBI Deduction

    Take 20% of qualifying business income. If a manual QBI amount has been entered (e.g., from a prior-year tax return), that amount is used directly and the income-source calculation is skipped.

    Auto-calc: Base QBI = Qualifying Business Income × 20%
Manual override: Base QBI = entered amount (bypasses income-source step)
    Example: $150k qualifying income × 20% = $30k base QBI deduction

  3. 3. Apply Taxable Income Limitation

    The QBI deduction cannot exceed 20% of taxable income before the QBI deduction itself. This cap applies in all income ranges.

    Taxable Income Before QBI = AGI − Standard or Itemized Deductions
Taxable Income Cap = Taxable Income Before QBI × 20%
Limited QBI = min(Base QBI, Taxable Income Cap)
    Example: Taxable income before QBI = $200k → cap = $40k Base QBI = $30k → Limited QBI = $30k (under cap)

  4. 4. Apply High-Income Phaseout

    For taxpayers whose taxable income before QBI exceeds the phaseout threshold, the deduction is reduced linearly. At or below the start threshold, the full limited QBI applies. At or above the end threshold, the deduction is $0. Within the range, the deduction is reduced proportionally. Phaseout thresholds (taxable income before QBI): • 2024: Single/HOH/MFS $191,950–$241,950; MFJ $383,900–$483,900 • 2025: Single/HOH/MFS $197,300–$247,300; MFJ $394,600–$494,600 Above the end threshold, the model returns $0 rather than attempting the W-2 wage or UBIA property limitation that IRC §199A provides for non-SSTB businesses.

    If income ≤ start threshold: Final QBI = Limited QBI (full deduction)
If income ≥ end threshold: Final QBI = $0
If start < income < end:
  Phaseout Ratio = (income − start) / (end − start)
  Final QBI = Limited QBI × (1 − Phaseout Ratio)
    Example: MFJ taxable income = $433,900 (midpoint of 2024 range) Phaseout ratio = ($433,900 − $383,900) / $100,000 = 50% Final QBI = $30,000 × (1 − 0.50) = $15,000

Real-world context

Tax Cuts and Jobs Act (TCJA)

The QBI deduction was introduced in the 2017 Tax Cuts and Jobs Act (Section 199A) to provide tax relief to pass-through businesses, putting them on more equal footing with C-corporations that received a rate reduction. The deduction is currently set to expire after 2025 unless extended.

IRS reference: IRS Publication 535 - Business Expenses

Income Thresholds and Phaseout

The full 20% QBI deduction is available to taxpayers whose taxable income falls below the phaseout start threshold: $383,900 (MFJ) or $191,950 (Single/HOH/MFS) for 2024. Above these amounts, the deduction phases out linearly over a $100,000 range (MFJ) or $50,000 range (all other filers). At the end of the phaseout range — $483,900 (MFJ) or $241,950 (Single) for 2024 — the deduction is eliminated entirely. Taxpayers above this range with non-SSTB businesses may still claim a deduction based on W-2 wages and UBIA property, but that limitation is not modeled.

Sunset Provision

The QBI deduction is currently scheduled to expire after 2025 unless Congress acts to extend the relevant TCJA provisions. Advisors should monitor legislative developments.

What drives the result

Schedule C Income
Base Data → Income

Business income directly qualifies for 20% QBI deduction

$100k Schedule C income → $20k QBI deduction → saves ~$4,400-7,400 in taxes

K-1 Income
Base Data → Income

Partnership/S-corp income qualifies for QBI deduction

$50k K-1 income → $10k QBI deduction

Manual QBI Entry
Base Data → Deductions

Manually entered QBI (from tax return) overrides auto-calculation for that year

Extracted $18k QBI from prior year return takes precedence over auto-calc

Assumptions

  • Manual QBI entries from a prior-year tax return take precedence over auto-calculation
  • Only positive qualifying income is included; losses do not generate a deduction
  • W-2 wage and UBIA property limitations (IRC §199A(b)(2)) are not modeled above the end threshold; the deduction is conservatively set to $0 rather than applying the limitation formula
  • SSTB income restrictions are not enforced; all qualifying income types receive equal treatment regardless of business type

Limitations

  • W-2 wage and UBIA property limitations not modeled (affects high-income non-SSTB businesses above the phaseout end threshold)
  • SSTB restrictions not applied (may overstate deduction for specified service businesses above the phaseout range)
  • Simplified calculation is accurate for most small businesses and all taxpayers below the phaseout threshold

Related

This page explains how Stratum models this calculation. It is educational material for financial professionals, not tax or legal advice, and tax law changes. Verify current figures against primary IRS sources before relying on them with a client.