The 401(k) Bracket Smoothing Strategy That Keeps Retirees Out of the 22% Tax Bracket for Life

A 66-year-old single woman, retired, with $1.1 million in a traditional 401(k), $300,000 in a Roth IRA, and $200,000 in a taxable brokerage arrives at the same question every retiree faces: which account do I tap first? The standard answer, taxable first, tax-deferred next, Roth last, costs her roughly $74,000 in lifetime federal income tax. The fix is a withdrawal sequence almost no one volunteers.

Her spending target is $72,000 a year. Social Security begins at 67 at $30,000. Two sequences produce two very different tax bills.

Sequence A: The conventional drawdown

Sequence A spends the $200,000 brokerage from age 66 through roughly 69, then turns to the 401(k). Social Security layers in at 67. By the time required minimum distributions begin at 73, the 401(k) has compounded near or above its starting balance. The mandatory distribution stacked on top of Social Security pushes her taxable income persistently into the 22% bracket and keeps it there through her 80s.

Modeled across ages 66 to 90, federal income tax under this path totals approximately $186,000. Up to 85% of her Social Security benefit becomes taxable in most of those years, and a single year of unusually large RMDs can clip the first IRMAA tier two years later.

Sequence B: Bracket smoothing before RMDs

Sequence B inverts the order during the early retirement window. From age 66 through 72, she draws $40,000 a year from the 401(k) and $32,000 from the Roth IRA. The 401(k) withdrawal, combined with the 2026 standard deduction of $18,150 available to a single filer aged 65 or older (the $16,100 base plus the $2,050 age add-on), lands her taxable income comfortably inside the 12% bracket. The Roth fills the remainder of her $72,000 spending tax free.

The brokerage sits untouched. By 73, the 401(k) balance is materially smaller, so her RMD plus Social Security mostly stays within the 12% bracket for the rest of her life. Lifetime federal tax comes to approximately $112,000, a saving of roughly $74,000 compared with Sequence A.

A new senior deduction worth knowing

The One Big Beautiful Bill Act, signed July 4, 2025, added a further wrinkle. For tax years 2025 through 2028, filers aged 65 or older can claim an additional $6,000 deduction on top of the standard deduction. The catch: it phases out at a rate of 6% for every dollar of MAGI above $75,000 for single filers. Under Sequence B, the retiree’s gross income of roughly $70,000 keeps her just below that threshold, preserving much of the deduction and pushing her effective tax rate even lower. That same MAGI headroom disappears under Sequence A, where heavy 401(k) withdrawals later in retirement push income well past $75,000 in many years.

Why the brokerage stays parked

The $200,000 taxable account is the most valuable inheritance vehicle she owns, because of the step-up in cost basis at death. Heirs receive a basis reset to the date-of-death value, and the embedded gains are never taxed. Spending it first to “let the 401(k) keep growing tax-deferred” forfeits that step-up while guaranteeing a larger taxable RMD pile later.

The IRMAA guardrail

Once Social Security begins, MAGI drives Medicare premiums. The first IRMAA threshold for a single filer in 2026 sits at $109,000 (confirmed at CMS.gov). Crossing it by a single dollar triggers an extra $81.20 per month on Part B and $14.50 per month on Part D, a combined surcharge of roughly $1,148 for the full year, based on income reported two years prior under the standard lookback. Higher tiers are steeper: total Part B premiums can reach $689.90 per month at the top bracket. Sequence B’s $40,000 401(k) draw plus $30,000 in Social Security keeps her well below that $109,000 line. A heavier Roth conversion in the same window would not.

Why the math is friendlier in 2026

Bracket adjustments, the higher standard deduction, and the expanded 12% bracket room all favor early drawdown this year. The One Big Beautiful Bill Act permanently locked in the current seven-bracket structure, eliminating the previously scheduled reversion to higher pre-TCJA rates. The 10-year Treasury yield, holding near 4.5% in mid-June 2026, and a federal funds target range of 3.50% to 3.75% support a moderate return assumption on the remaining 401(k) balance. Drawing it down earlier does not leave meaningful compounding on the table once the tax savings are netted out.

Three actions worth taking this month

1. Calculate the dollar ceiling of the 12% bracket using the $18,150 standard deduction available to a single filer aged 65 or older in 2026. The 12% bracket tops out at $50,400 of taxable income for single filers, which translates to roughly $68,500 in gross income before the standard deduction applies. That number is the annual pre-RMD 401(k) target. Withdraw to fill it, no more.
2. Project the first year Social Security and RMDs overlap. Every pre-RMD year between now and that date is the cheapest window available to liquidate tax-deferred dollars at 12%. Skipping those years is the expensive choice.
3. Run projected MAGI against both the $109,000 IRMAA threshold and the $75,000 phase-out floor for the $6,000 senior deduction. If a planned 401(k) draw or Roth conversion lands within $5,000 of the IRMAA line, the two-year Medicare surcharge often eats the marginal tax savings. Reference IRS Publication 590-B for RMD divisors and CMS.gov for current IRMAA tiers.

Editor’s note: This article was updated to correct the 2026 standard deduction for a single filer aged 65 or older to $18,150 (the $16,100 base plus the $2,050 age add-on), to add the new $6,000 OBBBA senior deduction and its $75,000 MAGI phase-out threshold, to reflect the current 10-year Treasury yield near 4.5% and Fed funds target range of 3.50% to 3.75%, and to update IRMAA Tier 1 surcharge figures to the confirmed 2026 amounts of $81.20 monthly for Part B and $14.50 for Part D.