A $2.4 Million 401(k) In Retirement Can Still Cost You Six Figures Without This Withdrawal Sequence

A user on r/DIYRetirement recently asked whether to spend from a Roth first “even though everyone says” to save it for last. The pushback in the thread got closer to the truth than the textbook answer. For a couple in their early 60s sitting on roughly $2.4 million spread across a taxable brokerage, a traditional 401(k), and a Roth, the textbook withdrawal order (taxable, then tax-deferred, then Roth) is usually the wrong one.

The reason is arithmetic. Deferring the 401(k) until required minimum distributions begin at 73 lets that balance compound into a tax problem the retiree cannot dodge. The right order rewrites the outcome. In one worked case (with $500,000 taxable, $1.6 million traditional, and $300,000 Roth) it saves roughly $187,000 in lifetime federal taxes and Medicare surcharges.

Why the Default Order Backfires

Follow the standard advice and the taxable account drains first. In the 63-to-72 window, the couple pays close to nothing: qualified dividends and long-term gains sit in the 0% bracket up to $98,900 of taxable income for a joint filer in 2026. It feels great.

The 401(k) keeps compounding. At a 6% return, $1.6 million grows to roughly $2.9 million by age 73. The first RMD, using the IRS Uniform Lifetime Table divisor of 26.5, lands near $109,000 of forced ordinary income on top of Social Security. Add a joint benefit near $60,000 (indexed by the 2026 COLA of 2.8%) and modified adjusted gross income clears $218,000. That trips the first IRMAA tier and pushes 85% of Social Security into taxable territory. Effective marginal rate: close to 40%.

Fill the 12% Bracket First

Reverse the sequence during the gap years between retirement and RMD age. Pull from the 401(k) first, but only enough to fill the 12% bracket. In 2026, that ceiling for a joint filer is $100,800 of taxable income, and the standard deduction adds another $32,200. Roughly $133,000 of gross 401(k) withdrawals per year comes out at a blended federal rate under 11%.

Cover any spending shortfall from the taxable account. Because ordinary income is already at the top of the 12% bracket, long-term gains realized to top off cash flow fall inside the 0% capital gains band up to that same $98,900 line and 15% thereafter. Leave the Roth alone. It compounds tax-free at whatever the portfolio earns; with the 10-year Treasury near 4.69% anchoring a balanced mix, the Roth roughly doubles by age 80.

By 73, the 401(k) has been drawn down to about $1.3 million instead of $2.9 million. The first RMD is closer to $49,000, MAGI stays under the IRMAA threshold, and Social Security taxation is capped at the 50% inclusion tier rather than 85%.

Where the $187,000 Shows Up

The savings live in three buckets:

1. Bracket arbitrage. Ten years of $133,000 pre-tax withdrawals at a blended 11% rate, versus the same dollars pulled later at 22% to 24% once Social Security and RMDs stack on top, saves roughly $130,000 in federal income tax.
2. IRMAA avoided. Staying under the $218,000 joint MAGI line preserves the base Medicare Part B premium of $202.90 per month per person. The first surcharge tier alone runs about $1,150 per person per year; avoiding two tiers across a decade for two enrollees is close to $45,000.
3. Social Security taxation reduced. Lower provisional income drops the taxable portion of benefits from 85% to 50% in several years, worth another $12,000 to $15,000.

Rerun both sequences with your own numbers before committing to either path. The gap widens the longer you wait to start.

Three Moves to Make Before December 31

1. Calculate the exact 401(k) withdrawal that fills the 12% bracket. For a joint filer in 2026, that is roughly $133,000 gross, minus other ordinary income, offset by the $32,200 standard deduction.
2. If you are between 60 and 63, use the SECURE 2.0 super catch-up. The total employee limit rises to $35,750 for that age band in 2026, and if you earned more than $150,000 in wages last year, the catch-up portion must go to a Roth 401(k) anyway. Route it there and start building the tax-free bucket you will lean on in your 80s.
3. If projected MAGI two years before Medicare enrollment sits between $200,000 and $218,000 joint, hire a fee-only tax planner. The two-year IRMAA lookback means the withdrawal or conversion you execute in 2026 sets your 2028 premium, and the planning fee pays for itself on that alone.

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