401(k) Rollover at Retirement: Timing, Roth Conversions, and IRMAA Planning

Most rollover guides focus on the job-change scenario: you're leaving one employer for another, here's the 60-day rule and the direct transfer checklist. Retirement is different. When you permanently leave the workforce, the rollover decision intersects with five other variables — your Rule of 55 access window, your Medicare enrollment timing, your IRMAA exposure, your Social Security filing strategy, and your RMD clock. Getting the sequence right is worth six figures over a 25-year retirement. Getting it wrong can permanently foreclose options that can't be recreated.

Is rolling to an IRA the right first move at retirement?

Usually yes — but not always immediately, and not always all at once. Two situations argue for delaying the rollover or keeping some money in the plan.

Rule of 55 income need. If you retire in the year you turn 55 or older, you can withdraw from that 401(k) without the 10% early distribution penalty — even if you're under 59½. This exception exists only inside the 401(k) plan under IRC § 72(t)(2)(A)(v).¹ The moment you roll to an IRA, the exception disappears. For anyone retiring between 55 and 59½ who needs portfolio income in the gap years, rolling first and drawing from the IRA later means paying 10% penalty on every dollar. See the Rule of 55 guide for how to coordinate partial rollovers around this exception.

Employer stock with NUA potential. If you hold highly appreciated employer stock inside the 401(k), the Net Unrealized Appreciation (NUA) strategy — taking the stock in-kind to a taxable account — is only available at distribution from the plan, not after a rollover. Once the stock goes into an IRA, the NUA strategy is gone. See the NUA calculator before initiating any rollover if you hold employer stock.

If neither of those applies, a direct rollover to a traditional IRA is typically the right structural move — it opens the full investment menu, enables Roth conversions on your schedule, and consolidates multiple old plans into a single account for simplified RMD management.

The Roth conversion runway: your window before Social Security and RMDs

Someone retiring at 62 today (born in 1964) reaches required minimum distribution age at 75 under SECURE 2.0 § 107.² If they defer Social Security to 70 for maximum benefit, they have an 8-year window where taxable income consists only of what they choose to draw or convert from their portfolio. For a married couple with no pension income, that window can mean converting at 12–22% marginal rates on income that would otherwise be taxed at 22–32%+ when RMDs eventually force it out.

2026 values: standard deduction $32,200 MFJ; 12% bracket ends at $100,800 taxable income; 22% bracket ends at $211,400. Source: IRS Rev. Proc. 2025-32.³

The point is not to maximize conversions in any single year — it's to fill the lower brackets systematically over a decade before the RMD clock starts. A $50,000/year Roth conversion for 10 years at 15% blended rate costs $75,000 in taxes. The same $500,000 forced out as RMDs at 28% blended rate costs $140,000. The difference — $65,000 — comes from identifying the window and using it intentionally.

IRMAA: the Medicare cliff that Roth conversions can trigger

Medicare's Income-Related Monthly Adjustment Amount (IRMAA) adds a surcharge to Part B and Part D premiums for beneficiaries above certain income thresholds. In 2026, the base Medicare Part B premium is $202.90/month.⁴ The first IRMAA tier begins at $109,000 MAGI for single filers and $218,000 for married couples — adding $81.20/month per person to Part B alone, or $974/year per person in extra premiums.⁵

IRMAA uses a two-year lookback. Your 2026 Medicare premiums are based on your 2024 MAGI. This means a Roth conversion you do in 2026 affects your 2028 Medicare premiums — which matters when you're planning conversion amounts for years immediately before and after age 65.

Practical planning rule: in the two years before Medicare enrollment (ages 63–64 for most people), convert up to but not over the IRMAA threshold. In the years when you're clearly below the threshold — ages 62–63 if you have no other income — convert more aggressively. The IRMAA cliff is a soft constraint that changes the year-by-year shape of the conversion plan, not the overall total.

RMD simplification: why rolling to IRA before 75 makes sense

Multiple old employer 401(k) plans each carry their own separate RMD calculation. Rolling them into a single traditional IRA consolidates all pre-tax balances into one account — one divisor from the Uniform Lifetime Table, one annual calculation, one distribution to manage. At age 75, the IRS Uniform Lifetime Table divisor is 24.6, producing an RMD of approximately $40,700 on a $1,000,000 balance.²

Beyond simplification, Roth conversions before RMD age directly reduce the traditional IRA balance subject to RMDs. Every dollar converted to Roth is a dollar that will never generate a forced taxable distribution. After SECURE 2.0 § 325, Roth 401(k) accounts also have no lifetime RMD requirement — and Roth IRAs have never had RMDs during the owner's lifetime.² Converting $500,000 over 10 pre-RMD years reduces annual RMDs by approximately $20,300/year at the age-75 divisor on a $500,000 lower balance — a material reduction in forced income.

Three real scenarios

Scenario 1: Age 62, $1.6M in 401(k), deferring Social Security to 70

Margaret and Tom retire together at 62. Combined 401(k) balances: $1.6M traditional. No pensions. Living expenses: $95,000/year, initially funded by a $350,000 taxable brokerage account to preserve the 401(k) for conversions.

Rule of 55 check: Both are 62; the exception is active. But because they have three years of living expenses in taxable accounts, they don't need 401(k) distributions before 59½. They execute a direct rollover of the full $1.6M to a traditional IRA in year one.

Roth conversion strategy (ages 62–70): With no earned income and no Social Security yet, their only income is approximately $8,000/year in taxable dividends. They convert $75,000/year — pushing total income to $83,000, well below the $218,000 IRMAA threshold and within the 12% bracket range. Over 8 years: $600,000 converted to Roth at a blended rate near 13%.

Why this matters at 75: Without conversions, their traditional IRA grows from $1.6M and generates RMDs in the $100,000+ range, stacking on top of Social Security to push them into the 22–24% brackets permanently. With $600,000 already in Roth (generating tax-free distributions), their traditional IRA balance is smaller and their annual tax bill on RMDs is substantially reduced. The Roth assets also pass to heirs income-tax-free, with no inherited-IRA 10-year RMD pressure.

Scenario 2: Age 58, $850K, early retirement with income need before 59½

Diane retires at 58. She has $850,000 in her former employer's 401(k) and needs $65,000/year for 18 months until she turns 59½, when IRA distributions become penalty-free. She has no other significant savings outside the retirement account.

The mistake: Rolling the full $850,000 to a traditional IRA first, then drawing $65,000/month. Every dollar distributed from an IRA before 59½ is subject to the 10% early distribution penalty (absent a SEPP arrangement or other exception). On $97,500 drawn over 18 months: $9,750 in avoidable penalties.

The right approach: Keep the 401(k) in the former employer's plan and draw the $65,000/year from it under the Rule of 55 exception — completely penalty-free. At 59½, roll the remaining balance (~$755,000) to a traditional IRA via direct transfer. Then begin Roth conversions during the 59½-to-65 window (5.5 years) before Medicare enrollment, staying below the $109,000 IRMAA threshold ($109,000 - $16,100 standard deduction = $92,900 in gross conversion income annually). Over 5 years at $80,000/year: $400,000 moved to Roth before her initial Medicare premium is set.

Scenario 3: Age 65, $1.2M, managing IRMAA at Medicare enrollment

Robert, single, retires at 65 and enrolls in Medicare. He has $1.2M in a 401(k) he wants to roll to a traditional IRA and begin converting. His Social Security benefit: $28,000/year (filed at 65). Approximately $23,800 of that is taxable at his income level (85% inclusion threshold, IRC § 86).⁶

The trap: A financial plan suggests converting $150,000 in year one. MAGI: $23,800 (taxable SS) + $150,000 (conversion) = $173,800 — crossing the $109,000 IRMAA threshold by $64,800. This adds $81.20/month to his Part B premium starting two years later. If that income pattern continues, the IRMAA surcharge persists indefinitely.

Better approach: Convert $80,000/year — MAGI of $23,800 + $80,000 = $103,800, staying below the $109,000 threshold. Over 10 years before RMD age at 75: $800,000 converted to Roth. His traditional IRA at 75 is meaningfully smaller, RMDs are lower, and he never paid an IRMAA surcharge. The 10-year tax cost of staying in the lower bracket is approximately $102,400 (at ~13% blended rate on $800K). The alternative — paying 22–24% on those same dollars as RMDs — would have cost approximately $176,000–$192,000. Difference: $70,000–$90,000 in lifetime tax savings, plus zero IRMAA exposure.

Rollover and Roth conversion checklist at retirement

1. Check Rule of 55. Retiring between 55 and 59½ and need income? Keep money in the 401(k) and draw from it directly; don't roll until 59½.
2. Check NUA. Highly appreciated employer stock? Model the NUA strategy before initiating any rollover. See the NUA calculator.
3. Check for an outstanding loan. Leaving with a 401(k) loan balance? A plan offset occurs; you may have until October 15 of next year to roll the offset amount and avoid taxes and penalty. See the loan offset guide.
4. Execute via direct rollover. Request a trustee-to-trustee transfer. Never take a check. The 20% mandatory withholding trap on indirect rollovers turns a mechanical step into a tax event. See the direct vs. indirect rollover guide.
5. Map your income over the next 10–13 years. Project Social Security start date, any pension income, and expected portfolio income. Identify years with the most bracket room below the IRMAA threshold.
6. Stay below IRMAA in the two years before 65. Ages 63 and 64 are the most sensitive — those MAGI figures set your initial Medicare premiums. Convert up to but not above $109,000 (single) or $218,000 (MFJ).
7. Convert aggressively during the low-income window. In the years before Social Security starts and before the IRMAA lookback reaches Medicare enrollment, you have the most room. Use it.

Sources

1. IRC § 72(t)(2)(A)(v) — Age-55 separation from service exception to the 10% early distribution penalty (law.cornell.edu)
2. IRS: Required Minimum Distributions FAQs — SECURE 2.0 RMD ages (73/75), Roth 401(k) RMD elimination, Uniform Lifetime Table
3. IRS Rev. Proc. 2025-32 — 2026 inflation-adjusted tax parameters: standard deduction $16,100/$32,200, bracket thresholds
4. CMS: 2026 Medicare Parts A & B Premiums and Deductibles — Part B base premium $202.90/month
5. SSA POMS HI 01101.020: 2026 IRMAA Sliding Scale Tables — Tier 1 thresholds $109,000 single / $218,000 MFJ; Part B surcharge +$81.20/month
6. IRC § 86 — Social Security benefit taxation: up to 85% of benefits included in gross income above provisional income thresholds

Tax values and Medicare premiums verified as of May 2026. SECURE 2.0 RMD age changes apply to distributions after 2022; Roth 401(k) RMD elimination effective 2024 per § 325.