The 401(k) to Roth Bracket Filling Strategy That Saves a $300,000 Earner Couple $145,000 in Taxes Over 8 Years

A traditional 401(k) balance represents future tax liability because withdrawals are taxed at the IRS-chosen bracket. A window exists between retirement and the first required minimum distribution, allowing retirees to choose the bracket for converted dollars. The approach is bracket filling: convert enough traditional 401(k) money to fill a lower marginal bracket each year, then stop before reaching the next bracket. With wages dropping to zero after retirement and Social Security delayed, taxable income can be kept low while conversions generate controlled income. Converting $50,000 per year for eight years moves $400,000 into a Roth, where it grows tax-free and avoids RMD taxation. The example estimates about $48,000 in tax cost at 12% versus higher taxes if left in the 401(k).

"Every dollar in that account is a future tax liability, and the IRS gets to pick the bracket. The good news: there is a 13-year window between now and the first required minimum distribution at 73 where the couple decides what bracket those dollars come out in. The strategy is bracket filling: converting traditional 401(k) money to Roth in the years when marginal rates are lowest, intentionally pushing taxable income up to the top of a chosen bracket and stopping there. Done right over eight post-retirement years, this couple saves roughly $145,000 in lifetime taxes."

"While both spouses are still working, household income lands them squarely in the 24% federal bracket. Conversions today are possible but expensive. The math changes the moment the paychecks stop. After retiring at 65, wages drop to zero. If Social Security is delayed to 67 or 70, the couple has a stretch of years with almost no taxable income on autopilot. The 2026 MFJ 22% bracket runs from $96,950 to $206,700 of taxable income, and the 12% bracket sits below it."

"With no wages, the couple can deliberately generate income by converting traditional 401(k) dollars to Roth, filling the 12% bracket each year before letting the 22% bracket touch a single dollar. Convert $50,000 per year for eight years, ages 65 to 73. That moves $400,000 out of the traditional 401(k) and into a Roth, where it grows tax-free forever and never triggers an RMD. Tax cost at the 12% marginal rate: roughly $48,000 across the eight years."

"The counterfactual is ugly. Leave that $400,000 in the 401(k), let it compound, and the IRS forces it out as RMDs starting at 73. Combined household income from Social Security, pensions, dividends, and mandatory distributions plausibly lands in"

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