Why Affluent Investors Over 60 Are Emptying Their 401(k)s Into a Roth Before the IRS Sets the Withdrawal Schedule

Picture a married couple, both 62, recently retired with about $1.6 million in a traditional 401(k), a paid-off house, and a plan to hold off on Social Security until age 70. Their taxable income this year is close to zero. Their 401(k) is the largest tax liability they own, and the IRS has already fixed the schedule for collecting it.

Because they were born after 1959, required minimum distributions start at 75. Until then, they control the timing. After that, the IRS does. The most expensive mistake they can make happens years before the first distribution: letting the low-income window close without converting.

Bracket Room Most Retirees Leave Empty

For 2026, a married couple filing jointly gets a $32,200 standard deduction. With no wages coming in, every converted dollar above that deduction fills the lowest brackets first, making the early retirement years a genuine arbitrage window.

The 22% bracket tops out at $211,400 of taxable income. The 24% bracket extends to $403,550, and only above that does the 32% rate begin. This couple can move a six-figure sum each year into a Roth without ever leaving the 24% bracket.

One wrinkle worth noting: the One Big Beautiful Bill, signed in July 2025, added a $6,000 deduction per qualifying taxpayer for those 65 and older, phasing out at 6% for income above $150,000 for joint filers. That provision does not help a 62-year-old today, but it does widen the conversion math once both spouses turn 65, provided conversions are sized to stay under the phase-out threshold.

What Waiting Until 75 Actually Costs

Leave the $1.6 million alone and it compounds tax-deferred, growing the eventual tax bill at the same pace as the portfolio itself. At 75, the first RMD lands on top of two full Social Security benefit payments and any other portfolio income, setting off a tax cascade that no longer has an easy escape valve.

Up to 85% of Social Security benefits becomes taxable once a couple’s combined income passes $44,000. Each additional RMD dollar can pull more of that benefit into taxable income. A couple nominally sitting in the 22% bracket can face a marginal rate approaching 40% once Social Security taxation is factored in.

A second layer comes from Medicare. IRMAA surcharges are set by income from two years earlier. In 2026, a couple whose income crosses the first IRMAA threshold ($218,000 of modified adjusted gross income for joint filers) pays an $81.20 per person per month surcharge on top of the standard $202.90 Part B premium. At the top bracket, that surcharge reaches $487.00 per person per month for Part B alone, before Part D charges are added. Large RMDs can lock a couple into those surcharges for the rest of their lives, with no ability to appeal except through a life-changing event.

Why 60 to 62 Is the Cheapest Conversion Window

The two-year IRMAA lookback creates a clean planning advantage. Income at age 62 sets Medicare premiums for age 64, a year before Medicare enrollment actually begins. That means conversions at 60, 61, and 62 carry no IRMAA cost whatsoever. Starting at 63, every conversion shows up on a Medicare premium bill two years later.

Those pre-63 years are the time to convert aggressively, filling the 24% bracket to its ceiling. From 63 until Social Security starts, conversions still make sense, but size them to land under the first IRMAA tier. (We looked closely at this quiet stretch from the final paycheck to the first RMD in a free Roth conversion guide here.)

Once money reaches a Roth, it exits the RMD equation for good. Since 2024, Roth 401(k) accounts carry no requirement to begin distributions at any age. Every dollar converted today is a dollar that can never increase a future RMD, trigger additional Social Security taxation, or push a couple into a higher IRMAA bracket.

Paying the Tax Bill From the Right Bucket

Pay conversion taxes from taxable savings, not from the conversion itself. Withholding tax from the converted amount reduces what actually reaches the Roth and sacrifices years of tax-free compounding.

With the 10-year Treasury yielding approximately 5%, that taxable cash carries a genuine opportunity cost. Over a decade or more, the Roth side of the ledger still wins that comparison for anyone expecting to land in the same or a higher bracket later, because the Roth’s growth faces no further federal tax.

Still Working at 60 to 63

If you are still on payroll, 2026 allows an extra $11,250 super catch-up contribution at ages 60 to 63, for a combined total of $35,750 in employee deferrals. Workers who earned more than $150,000 in 2025 are required to direct catch-up dollars to the Roth side. That mandatory routing is a built-in head start on the same long-term strategy.

Three Moves Before the Withdrawal Clock Starts

1. Map your timeline on one page. Write down the year RMDs begin (73 or 75, depending on birth year), the year you claim Social Security, and the year you turn 63. The years before all three events arrive are the cheapest conversion years you will ever have.
2. Convert to the top of the 24% bracket before 63. For married filers, that ceiling sits at $403,550 of taxable income in 2026. Run a projected return in November, once dividends and capital gains distributions are mostly known, and convert up to that line with a modest buffer.
3. Set an IRMAA ceiling from 63 forward. Pull the current Medicare IRMAA table each fall and size conversions to stay under the first tier, which starts at $218,000 of joint modified adjusted gross income in 2026. If your projected RMD at 75 would push you past the 32% bracket, a fee-only advisor who runs multi-year tax projections can more than pay for the engagement with a single well-timed conversion.

Editor’s note: This update corrects the IRMAA surcharge range to reflect the confirmed 2026 figures ($81.20 to $487.00 per person per month for Part B, with the first tier triggering at $218,000 of joint MAGI), updates the 10-year Treasury yield to approximately 5% based on late-October 2026 data, and adds context on the OBBBA’s new $6,000 senior deduction and its interaction with the Roth conversion bracket math.

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