A Roth conversion and the alternative minimum tax (AMT) rarely collide the way headlines suggest. Because a conversion adds ordinary income, and ordinary income is taxed the same under the regular system and the AMT, the conversion itself almost never creates a new AMT bill. What a large conversion can do is quietly raise your alternative minimum taxable income (AMTI) and shrink your 2026 exemption.
For most households, a Roth conversion does not trigger the alternative minimum tax. A conversion is ordinary income, which the regular tax and the AMT tax identically, so it does not create the preference items (like incentive stock options) that usually cause AMT. A very large conversion can still raise your AMTI and phase out part of your 2026 exemption, but that is different from producing an AMT bill.
What is the AMT, and how does it run alongside your regular tax?
The alternative minimum tax (AMT) is a parallel tax system that runs next to your regular federal income tax. You effectively calculate your tax twice, once under the ordinary rules and once under the AMT rules, and you pay the higher figure. The AMT uses a broader income base (AMTI), a large exemption, and a two-rate structure of 26% and 28% for 2026.
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The two-system parallel: you pay the higher of regular tax or tentative minimum tax
Under the AMT, you start from taxable income, add back certain items to reach alternative minimum taxable income (AMTI), subtract the AMT exemption, then apply the 26% and 28% rates to reach your tentative minimum tax on Form 6251. If that tentative minimum tax exceeds your regular tax, the difference is your AMT. You pay the higher of the two, never both in full.
2026 AMT numbers after the One Big Beautiful Bill
For 2026, the One Big Beautiful Bill (P.L. 119-21) reset the AMT figures. The exemption is $140,200 for married filing jointly and $90,100 for single filers, the exemption begins phasing out at $1,000,000 (MFJ) and $500,000 (single), and AMTI is taxed at 26% up to about $239,100 and 28% above that line.
| Filing status | 2026 AMT exemption | Phase-out begins | Exemption fully gone | 28% rate applies above |
|---|---|---|---|---|
| Married filing jointly | $140,200 | $1,000,000 AMTI | $1,280,400 AMTI | $239,100 AMTI |
| Single / head of household | $90,100 | $500,000 AMTI | $680,200 AMTI | $239,100 AMTI |
| Married filing separately | $70,100 | $500,000 AMTI | $640,200 AMTI | $119,550 AMTI |
Several older articles still cite the pre-OBBBA figures (a roughly $1.25 million threshold and a 25% phase-out rate). Those are wrong for 2026: the phase-out now starts at $1,000,000 (MFJ) and runs at 50 cents for every $1 of AMTI above the threshold.
Is a Roth conversion taxed as ordinary income under both systems?
Yes. A Roth conversion is fully taxable ordinary income in the year you convert, reported on Form 1040 and tracked on Form 8606. Ordinary income enters both the regular tax base and the AMTI base at the same value, so converting does not add an AMT preference item. The conversion raises income under both systems by the same amount.
Why ordinary income is treated the same for regular tax and AMT
The AMT was built to claw back specific tax breaks, not ordinary income. Wages, pension income, traditional IRA distributions, and Roth conversion income all appear in AMTI at full value, exactly as they do in regular taxable income. Because there is no add-back and no favorable AMT treatment to remove, a conversion moves both calculations in lockstep.
The real AMT triggers, and why a conversion is not one of them
Classic AMT triggers are items the regular system treats favorably but the AMT does not. The largest is the bargain element on exercised incentive stock options (ISOs). Others include interest on certain private-activity municipal bonds and specific depreciation or deduction add-backs. A Roth conversion is none of these. It is plain ordinary income, which is why it does not, by itself, create AMT.
So how CAN a Roth conversion affect your AMT?
A Roth conversion affects the AMT mainly through the exemption phase-out. Once your AMTI passes the 2026 threshold ($1,000,000 MFJ or $500,000 single), you lose 50 cents of exemption for every $1 of additional AMTI. A large conversion can push you into or through that phase-out range, raising the income actually exposed to the 26% and 28% rates.
Raising AMTI and phasing out your exemption above $1,000,000 (MFJ)
Below the phase-out threshold, adding conversion income to AMTI usually just increases regular tax, and the higher regular tax typically stays above the tentative minimum tax. Above $1,000,000 of AMTI (MFJ), each extra dollar also erases 50 cents of exemption, so $100,000 of conversion income can expose roughly $150,000 to AMT rates. That is where the interaction starts to matter.
When a large conversion actually crosses into AMT territory
A conversion crosses into AMT territory only when your tentative minimum tax exceeds your regular tax. That is unusual for pure ordinary income, because the top 2026 regular brackets (32%, 35%, and 37%) sit above the 26% and 28% AMT rates. It more often happens when a conversion stacks on top of ISO exercises or large capital gains that lift AMTI while regular tax stays comparatively low.
AMT vs. NIIT: two different taxes a conversion can touch
The AMT and the net investment income tax (NIIT) are two different taxes with different bases. The NIIT is a flat 3.8% on investment income once MAGI passes $200,000 (single) or $250,000 (MFJ). The AMT is a parallel income tax on AMTI at 26% and 28%. A Roth conversion is not net investment income, so it does not directly incur NIIT.
| Feature | AMT | NIIT |
|---|---|---|
| Type of tax | Parallel income tax | Surtax on investment income |
| 2026 rate | 26% / 28% | 3.8% flat |
| What it taxes | AMTI (broad income base) | Net investment income only |
| 2026 threshold | Exemption phases out above $1,000,000 MFJ AMTI | $250,000 MFJ MAGI ($200,000 single) |
| Does a conversion trigger it directly? | Rarely | No (a conversion is not NII) |
A conversion can still touch the NIIT indirectly by raising your MAGI, which may pull existing interest, dividends, and capital gains into the 3.8% tax. That mechanism is covered on our companion page, does a Roth conversion trigger NIIT, and in our 2026 NIIT guide.
How much can I convert to a Roth without triggering AMT?
There is no single dollar cap. How much you can convert before the AMT bites depends on your other AMTI, your filing status, and whether you hold AMT preference items. A practical approach is to model the conversion against your projected AMTI and stop where your tentative minimum tax would begin to exceed your regular tax, not simply at a regular tax bracket line.
Modeling the conversion against your AMTI, not just your regular bracket
Size the conversion by running both tax calculations at several conversion amounts. For each amount, compute regular tax and tentative minimum tax, then watch the gap between them. As long as regular tax stays higher, added conversion income is not producing AMT. Many high earners find the real constraint is NIIT, IRMAA, or the top ordinary brackets rather than the AMT.
The crossover point and a multi-year partial-conversion strategy
The crossover point is the conversion size at which one more dollar costs more than expected, whether from AMT exemption loss, the 3.8% NIIT, or an IRMAA tier. A common response is a multi-year partial-conversion plan: convert a measured amount each year to fill lower brackets and stay under the phase-out and IRMAA thresholds. See how much to convert to a Roth and the Roth conversion break-even analysis, plus broader strategies for high-income earners.
How to model your own conversion before you pull the trigger
Model a conversion before December 31, because a conversion is irreversible and cannot be undone after year end. Project your full-year income, add the proposed conversion, run both the regular and AMT calculations, and check the NIIT and IRMAA thresholds at the same time. A tax professional can run this on your actual figures and Form 6251.
- Project your full-year taxable income before any conversion.
- Add the proposed conversion amount to both regular taxable income and AMTI.
- Compute regular tax and tentative minimum tax (Form 6251) at that level.
- Confirm regular tax still exceeds tentative minimum tax; if it does not, reduce the conversion.
- Check the NIIT ($250,000 MFJ MAGI) and IRMAA ($218,000 joint MAGI) thresholds at the same income.
- Finalize before the December 31 deadline, since a conversion cannot be reversed and you cannot convert an RMD.
Timing matters as much as sizing. Our note on the 2026 Roth conversion deadline covers why the December 31 cutoff, not the April filing date, governs a conversion.
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Q3 Advisors is a registered investment adviser focused on retirement tax planning. This page is educational and is not advice; consult a qualified professional.
Frequently asked questions
Does a Roth conversion trigger the alternative minimum tax?
Usually not. A Roth conversion is ordinary income, and ordinary income is taxed the same under the regular system and the AMT, so the conversion does not create AMT preference items. A very large conversion can raise your AMTI and phase out part of your 2026 exemption, but it rarely produces an AMT bill on its own.
Does Roth conversion income count toward AMT?
Yes. Roth conversion income is included in alternative minimum taxable income (AMTI) at its full value, exactly as it is included in regular taxable income. Counting toward AMTI is not the same as triggering AMT: the income only matters if your tentative minimum tax ends up higher than your regular tax.
How much can I convert to a Roth without triggering AMT?
There is no fixed limit. The amount depends on your other income, filing status, and any AMT preference items such as incentive stock options. Model the conversion against your projected AMTI and stop where your tentative minimum tax would begin to exceed your regular tax. Many high earners reach NIIT or IRMAA limits first.
What income triggers the alternative minimum tax in 2026?
The AMT is driven by preference items, chiefly the bargain element on exercised incentive stock options, interest on certain private-activity municipal bonds, and specific deduction add-backs, combined with high AMTI. For 2026, the exemption ($140,200 MFJ) begins phasing out above $1,000,000 of AMTI (MFJ), which is where large amounts of income start to matter.
What is the AMT exemption for 2026?
For 2026, the AMT exemption is $140,200 for married filing jointly, $90,100 for single and head of household, and $70,100 for married filing separately. Under the One Big Beautiful Bill (P.L. 119-21), the exemption phases out at 50 cents per $1 of AMTI above $1,000,000 (MFJ) or $500,000 (single).
Is a Roth conversion taxed as ordinary income?
Yes. A Roth conversion of pre-tax IRA or 401(k) money is fully taxable as ordinary income in the year you convert, reported on Form 1040 and tracked on Form 8606. It is taxed at your ordinary brackets (up to 37% in 2026), not at capital gains rates, and it is not net investment income.
How is AMT different from the net investment income tax (NIIT)?
They are separate taxes. The AMT is a parallel income tax on AMTI at 26% and 28%. The NIIT is a flat 3.8% surtax on investment income once MAGI passes $200,000 (single) or $250,000 (MFJ). A Roth conversion is not net investment income, so it does not directly incur NIIT, though it can raise MAGI.
Can a Roth conversion reduce my AMT exemption?
Yes, if it pushes your AMTI above the 2026 phase-out threshold ($1,000,000 MFJ or $500,000 single). Above that line, you lose 50 cents of exemption for every $1 of additional AMTI, so a large conversion can shrink or eliminate the exemption. Below the threshold, the conversion does not change your exemption amount.
