The link between a Roth conversion and the QBI deduction runs through a single number: your taxable income relative to the 2026 Section 199A threshold. The same conversion dollar can free up a deduction that the “20% of taxable income” cap was holding back, or it can push a pass-through owner into the phaseout and shrink the 20% deduction. This guide maps that pivot so a business owner can locate the right zone before converting.
A Roth conversion does not change your qualified business income, but it raises taxable income, the figure that drives the second half of the Section 199A limit. If your “20% of taxable income” cap is currently binding, conversion income can enlarge the deduction. If you sit near or above the 2026 threshold, the same dollars can phase it down or, for a specified service business, erase it.
Does a Roth conversion reduce my QBI deduction?
A Roth conversion reduces the QBI deduction only when it lands on the wrong side of your taxable-income threshold. The conversion moves taxable income, not qualified business income itself. Below the 2026 line ($201,750 single, $403,500 married filing jointly) added income often frees up deduction; inside the phase-in range it shrinks the deduction; for a specified service business above the range it can zero it out.
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The reason is structural. Converting existing IRA dollars produces ordinary income that lifts taxable income, one of the two limits inside Section 199A, and never touches the qualified business income figure. The interaction is a question of geography: where your taxable income starts, and where the conversion moves it.
One separation matters up front. This page is about converting an existing IRA. Roth employer contributions to a solo 401(k) are a different lever, because a business-level retirement contribution reduces QBI directly. An IRA conversion does not. Sizing belongs in the same conversation as how much to convert to Roth and your broader Roth conversion strategy.
The two-limit rule behind every QBI outcome
Every Section 199A outcome traces to one formula: the QBI deduction equals the lesser of 20% of qualified business income or 20% of taxable income minus net capital gain. When taxable income is low, the second limit binds and caps the deduction. When taxable income is high, the wage, UBIA, and specified-service limits inside the first limit take over.
Written out, the rule is: QBI deduction = lesser of (20% of QBI) OR (20% of taxable income minus net capital gain). The “minus net capital gain” piece removes long-term capital gains and qualified dividends from the income side of the cap, because those already receive preferential rates. What remains is the ordinary-income base, and a Roth conversion adds squarely to it.
Because a conversion feeds only the taxable-income side of that formula, its effect flips depending on which limit is binding. Where 20% of taxable income is the smaller number, more income lifts the ceiling. Where the phaseout has engaged, more income invites the wage test or, for a specified service business, the specified-service reduction.
The 2026 Section 199A thresholds that decide everything
For 2026, IRS Revenue Procedure 2025-32 sets the full-deduction taxable-income line at $201,750 for single filers and $403,500 for married filing jointly. Above those lines the wage and specified-service limits phase in across ranges the One Big Beautiful Bill Act widened. Roth conversion income stacks on your other taxable income and pushes you rightward across every one of these lines.
2026 full-deduction lines: $201,750 single / $403,500 MFJ (Rev. Proc. 2025-32)
Below $201,750 single or $403,500 joint in 2026, the full 20% QBI deduction applies with no W-2 wage test and no specified-service restriction. This is the zone where a Roth conversion is most likely to help rather than hurt, because the only active limit is 20% of taxable income minus net capital gain.
The OBBBA-widened phase-in ranges: $75k single / $150k joint
The One Big Beautiful Bill Act (P.L. 119-21) widened the 2026 phase-in range to $75,000 for single filers (from $201,750 to $276,750) and $150,000 for joint filers (from $403,500 to $553,500). A wider range removes the deduction more gradually per dollar of income than the prior $50,000 single and $100,000 joint ranges, giving owners a longer runway before the limit fully bites.
| 2026 Section 199A | Single / HOH | Married filing jointly |
|---|---|---|
| Full 20% deduction up to | $201,750 | $403,500 |
| Phase-in range width (OBBBA) | $75,000 | $150,000 |
| Deduction fully limited above | $276,750 | $553,500 |
| Minimum deduction (QBI at least $1,000 + material participation) | $400 | $400 |
SSTB vs non-SSTB: total loss vs a W-2 wage / UBIA haircut
The threshold means two different things depending on the business. A specified service trade or business (SSTB: health, law, accounting, consulting, financial services, and similar fields) loses the deduction entirely above the top of the range. A non-SSTB does not vanish; above the threshold it becomes subject to the W-2 wage and 2.5% UBIA (unadjusted basis of qualified property) limit instead, which can leave a partial deduction rather than a total loss.
When a Roth conversion helps: freeing a taxable-income-capped deduction
When taxable income sits below your qualified business income, the 20% of taxable income limit is the smaller number and caps the QBI deduction below its full value. Adding ordinary income through a measured Roth conversion lifts that cap toward 20% of QBI and can restore deduction otherwise left unused, as long as you stop short of the 2026 threshold.
This case appears when other deductions, a soft business year for a spouse, or large itemized deductions have compressed taxable income below QBI. The 20% of QBI number looks generous, but the 20% of taxable income number is smaller, and the smaller number wins. Deduction is being surrendered simply because taxable income is low.
Worked example: filling taxable income up to your QBI limit
Consider Steve, single, with $200,000 of qualified business income but only $140,000 of taxable income and no net capital gain. His deduction is the lesser of $40,000 (20% of QBI) and $28,000 (20% of taxable income), so $28,000. A $60,000 Roth conversion lifts taxable income to $200,000, just under the $201,750 line, restoring the full $40,000. Figures are illustrative.
The conversion added $12,000 of QBI deduction ($40,000 minus $28,000) that the taxable-income cap had been suppressing. That restored deduction offsets part of the ordinary tax on the converted dollars, which is why an owner whose cap is binding may find the interaction works in their favor.
The “convert up to the threshold, then stop” ceiling
The helpful zone ends at the full-deduction line. Once a Roth conversion carries taxable income past roughly $201,750 single or $403,500 joint in 2026, additional dollars enter phaseout territory rather than adding deduction. That is the same fill-the-bracket-then-stop discipline behind a sound Roth conversion break-even analysis, applied to the 199A line rather than an ordinary bracket edge.
When a Roth conversion hurts: shrinking or erasing the deduction
For an owner already near or above the 2026 threshold, Roth conversion income runs the other way. Inside the phase-in range it triggers a partial reduction of the QBI deduction; for a specified service business, income above the top of the range zeroes it out. The true cost then includes a hidden second layer: the value of the deduction the conversion displaces.
An SSTB owner, or a non-SSTB owner limited by low W-2 wages, sitting at or just under the threshold has little room. Any ordinary income added on top, a conversion included, walks them into the phaseout. Here the question shifts from “how much deduction can I recover” to “how much am I willing to give up.”
How a conversion inside the phase-in range reduces the deduction
Inside the range, the deduction is cut by an applicable percentage equal to taxable income above the threshold divided by the range width ($75,000 single, $150,000 joint in 2026). A Roth conversion carrying you one-third through the range reduces a specified service deduction by roughly one-third. For a non-SSTB, the same movement phases in the W-2 wage and 2.5% UBIA limit instead of a flat reduction.
The SSTB cliff and the hidden second tax (marginal-cost math)
Carrying a specified service owner’s taxable income above $276,750 single or $553,500 joint erases the deduction entirely in 2026. Because that top sits in the 32% bracket or higher, the lost deduction is expensive. For an owner with $300,000 of QBI at a 32% rate, a fully displaced 20% deduction ($60,000) is worth $19,200 in tax, stacked on the conversion’s own ordinary tax. Illustrative only.
That $19,200 is the hidden second tax. The converted dollar is taxed at the ordinary bracket, and it simultaneously carries the value of the QBI deduction it removes (20% of the affected QBI multiplied by the marginal rate). Ignoring the second layer understates the real marginal cost of a conversion made inside or above the phase-in range.
How to size a Roth conversion around your QBI line (3-step decision rule)
Sizing a Roth conversion around the QBI deduction follows three steps: measure pre-conversion taxable income, locate it against the 2026 line ($201,750 single, $403,500 joint), and check whether the 20% of taxable income cap is binding (which tends to help) or the threshold sits below your income (which tends to hurt). The aim is knowing which regime applies before converting, not after.
- Compute taxable income before the conversion. Start with taxable income before any conversion and before the QBI deduction itself, then measure the distance to the 2026 line ($201,750 single, $403,500 joint), which is your available working room.
- Test whether the 20% of taxable income cap is binding. If taxable income is below QBI, the taxable-income cap is likely the smaller number, and a conversion up to the threshold may enlarge the deduction. If taxable income already exceeds QBI and sits near the line, added income tends to phase the deduction down.
- Separate non-SSTB headroom from the SSTB cliff. A non-SSTB with ample W-2 wages or qualified property may keep much of the deduction above the threshold, allowing more conversion tolerance. An SSTB owner faces the tighter constraint, because the deduction disappears completely past the top of the range.
Many owners then apply a fill-to-the-threshold heuristic: convert taxable income up to, but not through, the 199A line, and repeat across several years. Partial multi-year conversions can respect the threshold each year in a way one large conversion cannot. Timing matters too, since required distributions must come out first in an RMD year and cannot be converted, so many owners coordinate with the 2026 RMD rules and the December 31 conversion deadline.
Does conversion income change QBI itself, or only the taxable-income cap?
For an IRA Roth conversion, only the taxable-income cap. Qualified business income measures profit from your trade or business; converting IRA dollars neither adds to nor subtracts from it. The conversion moves taxable income, the second half of the 199A limit. Employer Roth contributions to a solo 401(k) are the opposite: a business-level deduction that reduces QBI directly.
That contrast is the differentiator many summaries blur. A solo 401(k) or SEP employer contribution lowers net business income and therefore QBI, roughly dollar for dollar, so it shrinks the 20% of QBI figure, and designated Roth treatment adds further nuance to which dollars are taxed now. An IRA conversion, by contrast, leaves QBI untouched and works only through taxable income, which is why many advisers avoid modeling the two as if they were the same move.
The neighboring effects: NIIT, IRMAA, and the $400 OBBBA minimum floor
A Roth conversion near the 199A line rarely acts alone. It is not itself net investment income, but it raises MAGI, which can expose other investment income to the 3.8% NIIT (over $200,000 single, $250,000 joint) and lift Medicare premiums through IRMAA (2026 surcharges begin above $109,000 single, $218,000 joint MAGI, on a two-year lookback). The OBBBA $400 minimum QBI floor sets a separate 2026 backstop.
The net investment income tax point is easy to miss: the conversion escapes the 3.8% surcharge directly, yet by lifting MAGI it can drag interest, dividends, and capital gains above the NIIT line. IRMAA works on a two-year lookback, so a 2026 conversion can shape 2028 Part B and Part D premiums (2026 Part B is $202.90 monthly before surcharges).
The OBBBA $400 minimum floor cuts the other way. Starting in 2026, a taxpayer with at least $1,000 of aggregate QBI from active qualified businesses in which they materially participate receives at least a $400 deduction (indexed after 2026), even where a conversion has compressed the standard calculation. Modeling these effects together is where the real answer lives.
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Frequently asked questions
These answers reflect the 2026 Section 199A rules under Revenue Procedure 2025-32 and the One Big Beautiful Bill Act. Each addresses how Roth conversion income interacts with the QBI deduction. Every figure is a 2026 amount, and the dollar examples are illustrative, not a projection of any specific result.
Does a Roth conversion affect the QBI deduction?
Yes, indirectly. A Roth conversion does not change qualified business income, but it raises taxable income, the second half of the Section 199A limit. Below the 2026 threshold ($201,750 single, $403,500 joint) it can enlarge a capped deduction; inside the phase-in range it reduces the deduction; for a specified service business above the range it can erase it.
Can a Roth conversion increase my QBI deduction?
It can, when your 20% of taxable income limit is binding. If qualified business income exceeds taxable income, the deduction is capped at 20% of taxable income. Adding Roth conversion income up to the 2026 threshold lifts that cap toward 20% of QBI. In the illustrative Steve example, a $60,000 conversion restored $12,000 of deduction.
What income level phases out the QBI deduction?
In 2026, the phase-in begins above $201,750 of taxable income for single filers and $403,500 for married filing jointly (Revenue Procedure 2025-32). The One Big Beautiful Bill Act widened the ranges, so the deduction is fully limited above $276,750 single and $553,500 joint. Between those points the wage and specified-service limits phase in.
Does Roth conversion income count as qualified business income?
No. Qualified business income is net income from a qualified trade or business you operate. Roth conversion income is ordinary income from converting a retirement account, not business profit, so it never counts as QBI. It affects the Section 199A deduction only through the taxable-income limit, not through the QBI figure itself.
How do you calculate the 20% QBI deduction?
The Section 199A deduction is the lesser of 20% of qualified business income or 20% of taxable income minus net capital gain. Above the 2026 threshold, a non-SSTB deduction is further limited to the greater of 50% of W-2 wages or 25% of wages plus 2.5% of UBIA. The smallest applicable figure is your deduction.
What is an SSTB for the QBI deduction?
A specified service trade or business (SSTB) is one where the principal asset is the reputation or skill of its owners or employees: health, law, accounting, consulting, financial services, performing arts, athletics, and similar fields. Above the top of the 2026 phase-in range ($276,750 single, $553,500 joint), an SSTB loses the QBI deduction entirely.
Do retirement plan contributions reduce QBI?
Employer retirement contributions to a solo 401(k) or SEP are a business-level deduction, so they reduce net business income and therefore QBI, roughly dollar for dollar. An IRA Roth conversion does not: it raises taxable income without touching QBI. Designated Roth treatment adds nuance, so confirm the mechanics with a qualified tax professional.
