The $39,200 Tax Cost That Saves $100,000 Later: A 401(k) Strategy for 60-Year-Olds

A single filer at 60, $250,000 of W-2 income, $2.1 million already stacked in a traditional 401(k), five years from retirement. The default move is to keep deferring at the 32% bracket and take the deduction. For pre-retirees with this profile, the better answer is to flip the next five years of contributions into the Roth 401(k) bucket and pay the tax now. The reasoning rests on a SECURE 2.0 rule change that quietly broke the old playbook, combined with a 2026 mandate that removes the choice entirely for high earners.

The Bill She Pays Up Front

Routing the $24,500 annual employee deferral into a Roth 401(k) instead of a pre-tax account costs her roughly $7,840 in additional federal tax each year at the 32% marginal rate, adding up to about $39,200 across five years. That is the real out-of-pocket number: a larger check to the IRS every year through 2030.

The pre-tax deferral feels like free money because it shrinks today’s bill. In practice it is a loan from the government, repayable at whatever rate applies when she withdraws. For someone who will spend retirement in the 22% to 24% bracket, deferring at 32% can still pencil out on paper. The break-even becomes far shakier once required minimum distributions, Social Security taxation, and IRMAA Medicare surcharges enter the picture.

Why the Math Flips After 73

Five years of $24,500 contributions compounded at 7% grows to roughly $145,000 by age 65. Left to compound another 20 years through age 85, that balance reaches about $455,000. In a Roth 401(k), every dollar of that $455,000 comes out tax-free after age 59 and one-half once the five-year clock is satisfied. In a traditional 401(k), the same $455,000 faces ordinary income tax at withdrawal, costing $100,000 to $110,000 in lifetime tax at a 22% to 24% RMD-era rate.

The upfront cost is roughly $39,200. The avoided tax is closer to $100,000. That gap widens further if spending pushes her into a higher retirement bracket. Congress permanently extended the Tax Cuts and Jobs Act bracket structure in July 2025 through the One Big Beautiful Bill Act, which eliminated the looming rate cliff that once made Roth conversions a deadline-driven decision. The case for going Roth is now structural: build the tax-free bucket while income is high and the bracket is known, before RMDs force the issue at 73.

The SECURE 2.0 Rule That Changed the Decision

Through 2023, Roth 401(k) balances were subject to required minimum distributions just like traditional balances. SECURE 2.0 eliminated that requirement for designated Roth accounts in employer plans starting in 2024, a change the IRS confirmed in Notice 2024-2. The Roth bucket now behaves like a Roth IRA inside the employer plan: it compounds untouched through her 70s and 80s and passes to heirs inside the 10-year tax-free window.

That single rule kills the strongest argument for staying pre-tax. The old playbook assumed both buckets would be force-drained at 73 under the IRS Uniform Lifetime Table. Only the traditional $2.1 million still faces that fate. A 73-year-old with a $2.5 million traditional balance faces a first-year RMD of roughly $94,000, calculated by dividing the prior year-end balance by the IRS distribution period of 26.5. That mandatory withdrawal, layered on top of Social Security and any other income, is exactly what trips the 85% Social Security taxation threshold and pushes modified adjusted gross income above the $109,000 IRMAA threshold for single filers, adding at least $1,148 per year in Medicare surcharges at the first tier alone.

Three Moves, In Order

1. Flip the next five years of contributions to the Roth 401(k) sleeve. Confirm the plan offers it. Most large plans do. The employer match still lands in the pre-tax bucket by default unless the plan has adopted the SECURE 2.0 Roth match election.
2. Route the SECURE 2.0 super catch-up entirely to Roth. Ages 60 through 63 unlock an enhanced catch-up of $11,250 on top of the $24,500 standard deferral for 2026, versus the standard $8,000 available to workers aged 50 to 59. There is an added reason to do this: starting in 2026, any employee earning more than $150,000 in FICA wages in the prior year is required by law to make all catch-up contributions on a Roth basis. At $250,000 of W-2 income, this person has no pre-tax catch-up option regardless. Paying tax on the $11,250 super catch-up at the 32% bracket buys outsized Roth growth because the four-year eligibility window is short and the compounding runway is long.
3. Map bracket-filling conversions for ages 65 through 72. Once W-2 income stops at retirement and before RMDs begin at 73, the marginal bracket likely drops to 12% or 22%. Converting traditional balances up to the top of the 24% bracket in those years shrinks the future RMD pile at a meaningful discount to today’s rate. The One Big Beautiful Bill Act also created a temporary $6,000 deduction for taxpayers aged 65 and older through 2028, which modestly lowers taxable income during those gap years and should be factored into each year’s conversion ceiling.

One trap to avoid: a large Roth conversion in any year Medicare premiums are being calculated. IRMAA uses a two-year lookback on modified adjusted gross income, so a $100,000 conversion at 63 can add thousands of dollars in Medicare surcharges at 65. For anyone who has not yet started a Roth IRA, opening one with even a small contribution during these working years also starts the five-year clock, so the tax-free holding period is satisfied well before distributions begin. The conversion plan needs to be modeled year by year, not executed in one move.

Editor’s note: This article was updated to note that the standard 401(k) catch-up contribution rose to $8,000 in 2026 (from $7,500 in 2025) for workers aged 50 to 59, reinforcing the relative value of the $11,250 super catch-up available at ages 60 to 63. The One Big Beautiful Bill Act’s temporary $6,000 deduction for taxpayers aged 65 and older through 2028 was added as relevant context for the gap-years conversion strategy in step three.

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