Roth Conversion Strategy for Ultra-High-Net-Worth Individuals

Not tax or legal advice. All figures verified for 2026. Consult a qualified tax advisor before implementing any strategy described here.

The conventional wisdom — "Roth conversions make sense when your current tax rate is lower than your expected future rate" — is mostly useless for a $30M+ family. At this level, your current rate is already 37%, and it's likely to stay there. By the conventional logic, you'd never convert.

That's wrong. For UHNW families, the Roth conversion question has two distinct parts that ordinary planning almost always conflates: is it worth paying tax now to save tax later on compounding? (that's the retirement planning question) and is it worth paying tax now to improve the tax outcome for my heirs? (that's the estate planning question). The second question often has a clear yes — even at 37%.

This guide covers when Roth conversions make sense at $30M+, how to identify low-income windows, the partial conversion math, the IRMAA trap, and how to think about Roth at the estate-planning level.

The estate planning lens

A traditional IRA has two tax problems. First, you paid no income tax on the contributions, so every dollar that comes out — whether by you in retirement or by your heirs after you die — is ordinary income. Second, if the account is large, required minimum distributions (RMDs) will force income recognition on a schedule designed by the IRS, not you. At $30M+, a $3M traditional IRA can generate $100,000+ of forced ordinary income per year starting at age 73, pushing you deeper into 37% territory just as you may be trying to manage IRMAA exposure.

A Roth IRA removes both problems. No RMDs during your lifetime. No income tax when your heirs take distributions. What you pay on conversion — the income tax bill — is leaving your estate and going to the government. For families with estates above the $15M exemption,¹ that tax payment is itself a form of estate reduction. You're prepaying a 37% federal tax to avoid a 40% estate tax on the same dollars — and the math on that is close even before counting the tax-free compounding inside the Roth for decades.

Inherited Roth IRA vs. inherited traditional IRA

For non-spouse designated beneficiaries (most adult children), both inherited Roth and inherited traditional IRAs fall under the 10-year rule: the account must be fully distributed by the end of the 10th year after the owner's death.

The critical difference under the 2024 final regulations (T.D. 10001): if the original owner of a traditional IRA died after their required beginning date (RBD — April 1 of the year after turning 73), beneficiaries must take annual RMDs in years 1–9 of the 10-year period, in addition to clearing the account by year 10.² This forces income recognition on a schedule even if the beneficiary would prefer to defer.

Roth IRA owners have no RBD — no lifetime RMDs are required — which means they are never considered to have died after their RBD under the regulations. Inherited Roth IRA beneficiaries always take distributions under the 10-year rule without any annual RMD requirement, regardless of how old the original owner was at death. The account can compound tax-free for the full 10 years, and all distributions are income-tax-free.

The implication: if you have a $5M traditional IRA and die at 80, your child inherits an account that generates forced ordinary income during the 10-year window and pays income tax on every distribution. A $5M Roth IRA inherited by that same child generates no income tax and can be deferred fully for 10 years of continued tax-free growth.

Low-income windows: when the math changes

Most UHNW families earn income continuously and are perpetually in the 37% bracket. But income is not always smooth. Specific life events create windows where ordinary income drops significantly — and those windows are conversion opportunities.

• Year of business exit. After selling a company, the gain is typically long-term capital gains taxed at 20% + 3.8% NIIT = 23.8%. Ordinary income for the year may be lower than normal if the business was the primary income source. If ordinary income before conversion falls into the 32% or 35% bracket, converting enough to fill those brackets is materially cheaper than converting at 37% in a normal year.
• Gap years. The year between winding down one venture and launching the next — or early retirement years before other income streams start — can produce genuine 24-35% bracket room.
• Charitable deduction years. A large DAF contribution in the year of a liquidity event can reduce AGI substantially, creating bracket room for a Roth conversion in the same year. This is a common combination: fund the DAF to offset the capital gains income, then convert IRA dollars at a lower effective rate. (Itemized deduction strategy — note that the DAF deduction reduces AGI for regular tax purposes but does not affect AMT.)
• Loss-harvest years. Large realized capital losses in a down market can offset ordinary income up to $3,000 per year — not a significant offset for UHNW. But if business losses, real estate passive losses carrying forward, or §1231 losses are available, those can create meaningful room.

Partial conversions: bracket filling in 2026

You do not have to convert an entire IRA at once. A partial conversion strategy targets a specific bracket ceiling, converting only enough to fill that bracket without crossing into the next tier.

For 2026 (married filing jointly), the bracket thresholds for taxable income are:³

The 2026 standard deduction for MFJ is $32,200,³ which reduces taxable income before the brackets apply. The practical calculation: estimate all other ordinary income for the year, subtract the standard deduction (or itemized deductions, whichever is larger), and convert enough to fill to the target bracket ceiling.

Example: A couple has $300,000 in ordinary income (W-2, partnership K-1), itemized deductions of $80,000, and a $400,000 IRA from a prior employer rollover. Taxable income before conversion: $220,000. The 35% bracket top is $768,700. Converting up to $548,700 of additional ordinary income would fill the 35% bracket without crossing into 37%. The 35% rate is still high, but for heirs who would pay 37% on the same distributions, the conversion breaks roughly even on rate — with the estate-tax and flexibility benefits tipping in favor of conversion.

The IRMAA trap

Income-Related Monthly Adjustment Amount (IRMAA) is a Medicare surcharge that adds $284–$690 per month to Part B premiums based on modified adjusted gross income (MAGI) from two years prior.⁴ Roth conversions increase MAGI in the year of conversion, potentially triggering surcharges two years later.

For 2026, IRMAA applies for MFJ filers with MAGI above $218,000.⁴ For UHNW families already well above that threshold, the marginal IRMAA impact of a Roth conversion is zero — you are already in the highest IRMAA tier regardless. But for a family who has retired and managed income down to $150,000 specifically to reduce IRMAA exposure, a $300,000 conversion would push them into higher IRMAA tiers for 2028 Medicare premiums. Run the IRMAA tier math before executing a large conversion in a managed-income year.

IRMAA operates on a two-year lookback: your 2026 Medicare premiums are based on 2024 income. A 2026 conversion affects 2028 premiums. Factor this into the timing when you identify a low-income window.

Roth 401(k): the no-RMD vehicle

SECURE 2.0 Act §325 eliminated required minimum distributions for Roth accounts inside employer plans (401(k), 403(b), TSP) starting in 2024.⁵ Previously, Roth 401(k) balances were subject to RMDs during the owner's lifetime (a quirk that drove most advisors to recommend rolling Roth 401(k) balances to Roth IRA at retirement). That requirement is gone.

For UHNW business owners with compensation income who maintain an active 401(k), designating contributions as Roth (if the plan allows) rather than pre-tax serves a compounding purpose: the after-tax Roth balance grows entirely inside a no-RMD, no-income-tax wrapper. At $24,500 per year in elective deferrals ($35,750 for ages 60–63 with the super catch-up),⁶ the amounts are modest relative to a $30M estate — but for assets you intend to leave to heirs rather than spend, Roth 401(k) is strictly better on an after-tax basis than pre-tax 401(k).

Mega backdoor Roth for business owners

For owners of businesses with 401(k) plans that permit after-tax contributions and in-service distributions or in-plan Roth conversions, the mega backdoor Roth allows contributions far above the $24,500 elective deferral limit.

The mechanics: the IRS §415 annual additions limit caps total contributions (employee + employer) at a higher ceiling. After making the maximum pre-tax or Roth elective deferral, additional after-tax non-Roth contributions can be made up to the §415 limit. Those after-tax contributions are then immediately converted to Roth inside the plan (in-plan Roth conversion) or rolled out to a Roth IRA on distribution. The basis has already been taxed; only future earnings inside the Roth are at issue.

Not all 401(k) plans permit this. Solo 401(k) plans for self-employed individuals typically do allow after-tax contributions and in-service distributions — the owner controls the plan document. For owners of businesses with rank-and-file employees, the plan must be tested for non-discrimination, which can limit after-tax contributions unless sufficient matching or profit-sharing is provided to lower-paid employees.

A qualified plan advisor should model whether the economics support the non-discrimination contribution cost for a mega backdoor Roth strategy in a multi-employee plan.

State tax timing

State income tax adds materially to Roth conversion cost. California taxes Roth conversions as ordinary income at up to 13.3% — converting $1M in California costs $370,000 in federal tax plus $133,000 in state tax = $503,000 total, or 50.3 cents per dollar converted.

For families executing a California domicile change (see our state tax domicile change guide), the sequencing question is whether to convert before or after establishing a new domicile in a zero-income-tax state. The answer is almost always after: converting in Florida or Nevada eliminates the state tax component entirely. However, California's Franchise Tax Board is aggressive about partial-year residency and source-income rules — if income is traced to California-source activity, it may remain taxable in California regardless of where you live during the conversion. Work with a state tax specialist before assuming a domicile change eliminates California tax on a conversion.

When Roth conversion doesn't make sense at $30M+

Roth conversion is not universally right for UHNW families. Several conditions argue against it:

• Charitable intent for the IRA. If you plan to leave your traditional IRA to a DAF, private foundation, or charitable remainder trust, no income tax will ever be due on those dollars — the charity receives them income-tax-free. Converting a charity-destined IRA means paying 37% on dollars that never needed to be taxed. The correct strategy in this case is to use the IRA for charitable bequests and leave appreciated portfolio assets (which get a step-up at death under §1014) to heirs.
• Estate tax exemption available. If your estate is comfortably below $15M (the current OBBBA-permanent exemption for individuals, $30M for a couple with portability),¹ the estate-tax-savings argument disappears. Without estate tax pressure, the conversion math requires a genuine rate-differential thesis.
• No obvious low-income window. Paying 37% + 13.3% (California) = 50.3% to save heirs 37% on the same distributions is not a winning trade. Without a meaningful tax-rate differential, conversion is costly.
• Assets are in a taxable account, not an IRA. Most UHNW wealth is taxable already — publicly traded securities in brokerage accounts, real estate, business interests. Traditional IRAs are typically a smaller percentage of a $30M+ estate than for a middle-class retiree. The compounding impact of Roth conversion is limited if the IRA itself is a small fraction of total wealth.

Coordination with other UHNW structures

Roth conversion does not operate in isolation. At $30M+, the right answer almost always involves coordinating across multiple strategies in the same tax year:

• DAF contributions + Roth conversion in the same year. Fund the DAF with appreciated securities (no capital gains tax, full FMV deduction up to 30% of AGI) in a high-income year to create itemized deduction room, then convert IRA dollars that would otherwise be 37% income — a partial rate arbitrage.
• QOZ deferral + conversion. In a year with large capital gains deferred into a Qualified Opportunity Fund, the income recognition on those gains is shifted to a future year (year 5 or later). This can temporarily lower taxable income in intervening years, creating bracket room for a conversion. See our QOZ calculator for the deferral mechanics.
• CRT + conversion. Funding a charitable remainder trust with an appreciated position eliminates capital gains on that position and generates a charitable deduction. If the deduction creates room inside a lower bracket, a Roth conversion in the same year can fill that room. See our CRT calculator for deduction estimates.
• Estate plan integration. At $30M+, Roth balances sitting in a bypass trust or irrevocable life insurance trust (ILIT) require specific planning — not all trust structures can hold Roth IRAs effectively. Inherited Roth IRA distributions into a trust may be taxed at the compressed trust income rate (37% at $16,550 of income in 2026) rather than the beneficiary's individual rate. Consult your estate attorney before naming a trust as IRA beneficiary without reviewing the tax treatment.

Sources

1. Estate and gift tax exemption $15M per individual (permanent under OBBBA, July 2025). IRS Estate and Gift Tax
2. Inherited IRA annual RMD rules when decedent past RBD — T.D. 10001 (July 2024), IRS; 10-year rule under SECURE Act (IRC §401(a)(9)(H)).
3. 2026 federal income tax brackets and standard deduction (MFJ $32,200) — IRS Rev. Proc. 2025-32; confirmed via Tax Foundation 2026 Brackets.
4. 2026 IRMAA brackets — Part B premiums begin at MFJ MAGI $218,000 (based on 2024 income). Kiplinger IRMAA 2026; Medicare.gov Part B premiums.
5. SECURE 2.0 Act §325: Roth designated accounts (401(k)/403(b)/TSP) no longer subject to required minimum distributions during owner's lifetime, effective 2024. IRS Roth comparison.
6. 2026 401(k) elective deferral $24,500; catch-up (50+) $8,000; super catch-up (ages 60–63) $11,250 — IRS IR-2025-245.

Values verified as of May 2026. Tax law changes frequently — confirm current-year figures with a qualified tax advisor before acting.