Roth Conversion Rules 2026: The Complete Guide

Most people searching for "Roth conversion rules" are trying to answer one of two questions: Can I do this at my income level? And will I get in trouble if I do it wrong? This guide answers both — walking through the 10 rules that govern every Roth conversion and the specific 2026 changes that affect the math.

Rule 1: There is no income limit for Roth conversions

This is the most important rule, and the most commonly misunderstood. Anyone can convert a traditional IRA to a Roth IRA regardless of income. There is no phase-out, no ceiling, no cap. A surgeon earning $900,000/year can convert. A retired CEO with $5 million in a traditional IRA can convert. Income is irrelevant.

The confusion comes from conflating two separate transactions:

This asymmetry is what makes the Roth conversion golden window so powerful for high-income earners. You could never have contributed directly to a Roth during your working years — your income was too high. But now, in retirement, when income has dropped and the traditional IRA has grown to $1M+, you can systematically move that money into tax-free growth through conversions.

This is also the mechanism behind the backdoor Roth: contribute to a non-deductible traditional IRA (no income limit on contributions, just no deduction at high income), then immediately convert to Roth. The conversion step has no income limit.

Rule 2: No annual dollar cap on conversions

You can convert $10,000 or $2,000,000 in a single year. The IRS imposes no ceiling. The only constraint is the amount available in your traditional IRA or 401(k).

In practice, the question is not "how much can I convert?" but "how much should I convert this year?" That answer comes from your tax bracket. Converting $2 million in one year would push income into the 37% bracket. Converting $80,000 might fill the 22% bracket exactly. The tax bracket calculator on this site helps you find the optimal conversion amount for your situation.

Rule 3: Converted amounts are ordinary income — in the year of conversion

When you convert pre-tax IRA funds to Roth, the converted amount is added to your gross income for that tax year, taxed at ordinary income rates. This is not capital gains treatment, not a flat rate, not spread over future years — it all lands in the current tax year at your marginal rate.

Practical implications:

• Pay taxes from a taxable account, not from the IRA. If you withhold taxes from the converted IRA funds, you're effectively distributing that portion — which shrinks what actually gets into the Roth and may trigger a 10% early withdrawal penalty if you're under 59½.
• A large conversion can cross bracket boundaries. Converting $200,000 might move from the 22% bracket into the 24% and then 32% brackets in the same year. The calculator shows you where the thresholds are.
• Estimated taxes may be required. A large conversion can create a tax underpayment penalty if you haven't adjusted withholding or paid estimated taxes in Q4.
• After-tax (basis) amounts are not taxed again. If your traditional IRA includes non-deductible contributions tracked on Form 8606, that after-tax basis is not taxed on conversion. The pro-rata rule (Rule 6 below) determines how basis is allocated across conversions.

Rule 4: RMDs must come first — and the RMD itself cannot be converted

If you are subject to required minimum distributions (RMD age is 73 for those born 1951–1959; 75 for those born 1960 or later under SECURE 2.0²), two sub-rules apply:

Example: You have a $1M traditional IRA. Your 2026 RMD divisor from the Uniform Lifetime Table is 26.5 (age 73), giving an RMD of $37,736. You want to convert $100,000. You must first take the $37,736 RMD (taxed as income, not converted), then convert up to $100,000 from the remaining balance. Your total ordinary income from IRA activity this year: $137,736.

This is why heavy conversions before RMDs begin — the golden window from retirement to age 73/75 — are so tax-efficient. There's no mandatory distribution forcing income, so every dollar converted is a voluntary choice to pay tax now rather than later.

Note: Roth IRAs themselves are exempt from lifetime RMDs. Roth 401(k) accounts were also exempted starting 2024 under SECURE 2.0 § 325.²

Rule 5: The 5-year rule — and why it's often irrelevant for this audience

There are actually two separate 5-year rules for Roth accounts. They're frequently conflated, and for this site's core audience (age 55–72), one of them almost never matters.

5-Year Rule #1 — Roth IRA earnings clock: To withdraw Roth IRA earnings tax-free, a 5-year period must have passed since your first Roth IRA contribution or conversion, AND you must be 59½ or older. If you opened your first Roth IRA today at age 62, you can't take tax-free earnings distributions until age 67. Contributions and converted principal can always come out first (basis ordering rules).

5-Year Rule #2 — Conversion penalty clock: Each conversion has its own 5-year period for penalty-free withdrawal of the converted principal. Withdrawing converted principal before 5 years (and before age 59½) triggers a 10% penalty. But this only matters before age 59½. Once you're 59½, the penalty clock on conversions is irrelevant — you can withdraw converted principal at any time with no penalty.

Full details with worked examples: The 5-Year Rule on Roth Conversions.

Rule 6: The pro-rata rule applies if you have any pre-tax IRA balance

If your total IRA balances include both pre-tax (deductible) funds and after-tax (non-deductible) basis, you can't selectively convert only the basis. The IRS treats all your traditional IRAs as one pool and taxes each conversion proportionally.

Example: $1.5M total traditional IRA value, $75,000 after-tax basis → 95% of every dollar converted is taxable. You can't convert just the $75,000 basis tax-free while leaving the pre-tax dollars behind.

The workaround: roll pre-tax IRA balances into a 401(k) plan (if your plan accepts rollovers), which removes them from the pro-rata calculation. The remaining basis can then be converted tax-efficiently.

Full details: The Pro-Rata Rule and Roth Conversions.

Rule 7: You cannot undo a Roth conversion — recharacterization is gone

Before 2018, you could "recharacterize" a Roth conversion — essentially undo it by October 15 of the following year if the market declined or your tax situation changed. This was a valuable option that let you convert, wait to see how markets performed, and reverse if the account dropped in value.

The Tax Cuts and Jobs Act (TCJA), effective for conversions after December 31, 2017, eliminated recharacterization of Roth conversions permanently.³

What this means: once you convert, it's done. You pay taxes on the converted amount regardless of what happens to the market afterward. This makes timing and sizing conversions more consequential — converting a large amount in a market peak, then watching values drop 30%, means you overpaid taxes relative to the converted asset's actual value. Year-by-year planning with smaller, regular conversions manages this risk better than large lump-sum conversions.

(Note: recharacterization still works in one direction — you can recharacterize a contribution between traditional and Roth IRA. Only conversion recharacterization was eliminated.)

Rule 8: The OBBBA senior deduction (2025–2028) creates a hidden marginal rate on conversions

The One Big Beautiful Bill Act (OBBBA, July 2025) created a temporary additional deduction for taxpayers age 65 or older:⁴

The relevance to Roth conversions: every dollar you convert above the phase-out threshold doesn't just add income at your marginal rate — it also reduces the senior deduction by $0.06 for every dollar over the threshold. At a 22% marginal rate, converting a dollar in the phase-out zone costs 22¢ in federal tax plus 22% × $0.06 = 1.3¢ in lost deduction value, making the true marginal rate approximately 23.3%. At higher brackets the effective rate magnification is larger.

For married couples with combined income already near $150,000, Roth conversions that push MAGI above $150,000 will trigger phase-out. For those planning year-by-year conversions through 2028, the senior deduction threshold is a new planning variable alongside IRMAA tiers and bracket boundaries.

Advisors typically model this as part of a multi-year tax projection — factoring in senior deduction availability (expiring after 2028), IRMAA lookback, and bracket thresholds simultaneously.

Rule 9: IRMAA — conversion income affects Medicare premiums two years later

Medicare Part B and Part D premiums are income-tested. A large Roth conversion in 2026 raises your 2026 MAGI, which the Social Security Administration uses to set your 2028 Medicare premiums. The surcharges are called IRMAA (Income-Related Monthly Adjustment Amount).

The 2026 IRMAA tier thresholds for single filers begin at $106,000 MAGI, adding $70.90/month to Part B premiums ($849/year). For married joint filers, the first tier begins at $212,000. Tiers stack higher as income rises, with the highest surcharge adding $443.90/month per person.

Crossing an IRMAA tier — even by $1 — triggers the full surcharge for the entire year. This creates a series of "IRMAA cliffs" that smart conversion planning navigates around.

Full details with cliff amounts by tier: IRMAA-Aware Roth Conversion Calculator.

Rule 10: Conversions must be completed by December 31

Unlike IRA contributions (which can be made until April 15 of the following year), a Roth conversion must be completed — funds transferred and conversion election made — by December 31 of the tax year you want it to count in.⁵

Practical implications for year-end conversion planning:

• Don't wait until late December. Custodians can take 3–5 business days to process conversions, especially around holidays. Requests submitted after December 28 may not process before year-end.
• Before converting at year-end, confirm your total 2026 income — W-2s, Social Security, investment income, any Roth conversions already done — to verify your exact bracket position and IRMAA tier.
• If you're on the fence about size: you can do multiple conversions in the same year. If you convert $50,000 in March and want to do more in November after seeing your income picture more clearly, that's entirely permissible.

How the rules interact: a planning framework

In practice, Roth conversion planning for someone with a large traditional IRA involves managing four constraints simultaneously:

1. Federal tax bracket ceiling — stay below the bracket you want to avoid (typically the 24%→32% jump)
2. IRMAA tier floor — stay below the next Medicare surcharge threshold (or accept it knowingly)
3. OBBBA senior deduction phase-out (2025–2028 only, age 65+) — phase-in above $75K/$150K
4. State tax tier — if your state has graduated rates, the same cliff analysis applies at the state level

The right conversion amount is often a number that navigates all four simultaneously. That's why the advisors in our network build multi-year tax projections — the optimal 2026 conversion depends on projected income in 2027, 2028, and beyond, including RMD onset, Social Security claiming date, and expected portfolio growth.

Summary: Roth conversion rules at a glance