Roth Conversion Math for Couples Trying to Empty a $1.4 Million 401(k) Before RMDs

Affluent retirees are revisiting Roth conversions as a way to use the years between retirement and required minimum distributions, or RMDs, to move money out of traditional 401(k)s on their own timetable. A widely shared 2026 example describes a married couple, both 62 and already retired, using that gap before age 73 to convert a $1.4 million pre-tax balance while staying mindful of federal tax brackets and Medicare premium surcharges.

The example, published by AOL and 24/7 Wall St., is not a new IRS program or rule change. It is a planning framework built around 2026 tax thresholds, the current RMD starting age of 73, and Medicare's two-year lookback for income-related monthly adjustment amounts, known as IRMAA.

What Changed

The discussion has picked up because several moving parts now line up in a way that can make the pre-RMD window more valuable for higher-income households. Under the 2026 figures cited in the article, married couples filing jointly pay 10% on the first $24,800 of taxable income, 12% up to $100,800, and 22% up to $211,400 of taxable income. With a $32,200 standard deduction, that means a couple could have as much as $243,600 of gross income and still stop at the top of the 22% bracket.

The article also says those bracket structures are now permanent beyond 2026 after the One Big Beautiful Bill Act, signed in July 2025, kept the Tax Cuts and Jobs Act framework in place. That reduces one source of uncertainty for households considering a series of annual conversions rather than a one-time move.

The basic premise is straightforward: if a retired couple has little current taxable income before Social Security and RMDs begin, those years can be unusually flexible for recognizing income deliberately through Roth conversions.

Who Is Affected

The example is aimed at couples in their early 60s with large traditional retirement balances and a temporary drop in taxable income after leaving work. In the scenario described, both spouses are 62, both are retired, neither has pension income yet, and neither has started Social Security. That leaves 11 years before RMDs begin at 73.

For households in that position, waiting can raise the eventual tax bill simply because the pre-tax account may keep growing. The article assumes a 6% annual growth rate, which would take $1.4 million to roughly $2.7 million by age 73. Using the IRS Uniform Lifetime Table factor of 26.5 for the first RMD year, that would produce an initial required withdrawal near $100,000.

That withdrawal would not arrive in isolation. By then, many couples would also have two Social Security checks in the picture, and the article notes that up to 85% of Social Security benefits can become taxable. In that fact pattern, forced withdrawals can keep a household in the 22% or 24% bracket for years, while also increasing the odds of Medicare premium surcharges.

The After-Tax Math

The article's worked example uses a bracket-filling approach rather than converting the entire account at once. If a married couple converts enough each year to generate $243,600 of gross income, the federal tax bill would be about $35,932 for that year, according to the example. That is an effective rate of roughly 15% on the conversion amount.

Over seven years, converting $243,600 annually would move about $1.7 million from pre-tax accounts to Roth accounts, enough in the example to absorb both the current $1.4 million balance and a portion of future growth. The article estimates a lifetime federal tax cost of about $250,000 under that approach.

Example: a married couple with minimal taxable income at 62 might convert enough to fill the 22% bracket in one year, then repeat that process over several years rather than waiting for RMDs to force withdrawals later. Whether that lowers lifetime tax depends on future returns, Social Security timing, filing status after the first spouse dies, and state taxes if any apply.

Why IRMAA Matters

A key limit in the example is Medicare's IRMAA threshold. For 2026, the article says a married couple crosses the first IRMAA tier when modified adjusted gross income exceeds $218,000. That adds roughly $81 per person per month to the standard Part B premium of $202.90. The article also notes that the next tier pushes total Part B premiums above $400 per person.

That is why the example focuses so closely on staying near the top of the 22% bracket. The cited $211,400 ceiling for taxable income sits below the $218,000 IRMAA threshold for modified adjusted gross income, creating a narrow band where a conversion may stay efficient without triggering higher Medicare premiums later.

There is one timing point highlighted in the article: conversions done in the calendar year each spouse turns 62 would not affect Medicare premiums at 65 because of the two-year lookback. On that reasoning, some households model a larger conversion in that year, potentially filling the 24% bracket up to $403,550 of taxable income, then using smaller annual conversions afterward.

What to Watch Next

What matters from here is not a new law but execution risk. Small differences in income can affect both tax brackets and IRMAA. The article argues that households considering this strategy often discuss three issues with a CPA or financial planner: whether the age-62 year justifies a larger conversion, how much room remains each year beneath the 22% bracket and IRMAA threshold, and whether taxes can be paid from taxable assets instead of from the retirement account itself.

The broader point is that affluent couples with large pre-tax balances may have a short stretch in their early retirement years when taxable income is unusually low and tax planning flexibility is unusually high. If that window closes before conversions are evaluated, the decision may effectively be made later by RMD rules, Social Security taxation, and Medicare means testing.

After TAX is an independent publication. Articles are general information, not tax, legal or investment advice. Consult a licensed professional about your situation.