The 401(k) Tax Bomb That Hits Retirees With $2.5 Million: $7,862 Monthly RMDs Plus IRMAA Surcharges

A 73-year-old single retiree sitting on $2.5 million in a traditional 401(k) is about to learn that the IRS does not care whether the income is needed. The first required minimum distribution lands at roughly $94,340, or about $7,862 a month, whether the retiree spends a dime of it or not.

The real damage shows up on every other line of the tax return.

Where the $94,340 Comes From

The IRS Uniform Lifetime Table divides the prior year-end balance by 26.5 at age 73. On $2.5 million, that is the $94,340 figure. Each subsequent year the divisor shrinks while a healthy portfolio keeps growing, which is why the cumulative RMD-driven tax bill over 20 years clears $400,000 for a balance of this size.

Stack the first-year RMD on a modest $30,000 Social Security check. At this income level, 85% of the benefit, or $25,500, becomes taxable. Ordinary income now totals $119,840 before any deduction.

After the 2026 single-filer standard deduction with the age 65 add-on (roughly $16,550, worth verifying against the final IRS table), taxable income lands near $103,290. Federal income tax comes to roughly $17,600, placing the top dollars in the 22% bracket.

The IRMAA Trap Hiding in the MAGI Line

Medicare Part B and Part D premiums step up at fixed MAGI thresholds with a two-year lookback. The first single-filer tier in 2026 sits near $109,000. The RMD plus taxable Social Security clears it, adding roughly $890 a year in combined Part B and Part D surcharges. Higher tiers push the annual penalty into the $2,000 to $5,000 range per person.

Combine the 22% federal bracket, taxable Social Security creep, and IRMAA, and the effective marginal rate on the last slice of the RMD pushes toward 40%. That is the cascade most retirees do not model when they are 60 and admiring the 401(k) balance.

Inflation Makes the Forced Withdrawal Worse

The 10-year Treasury yield sits at 4.41% as of early May, and core PCE inflation has risen from 125.79 in May 2025 to 129.28 in March 2026, the Fed’s preferred measure still running above target. A fixed $94,340 distribution buys less each year while the dollar amount of the RMD itself ratchets higher as the divisor falls. The retiree pays more tax on a check whose purchasing power is shrinking.

Three Moves That Actually Change the Math

1. Bracket-fill Roth conversions between 60 and 72. Every dollar converted in the 12% or 22% bracket before RMDs begin is a dollar that never shows up in the divisor at 73. Converting $50,000 a year for a decade can knock 20% off the eventual RMD and keep MAGI under the first IRMAA tier in retirement.
2. Use QCDs once RMDs begin. A qualified charitable distribution sends up to $108,000 in 2026 directly from a traditional IRA to charity, satisfying the RMD with zero taxable income. The 401(k) itself does not qualify, so rolling part of the balance to an IRA at retirement is the prerequisite. For charitably inclined retirees, this is the single highest-leverage tax move available after 73.
3. Park up to $210,000 in a QLAC. A qualifying longevity annuity contract lets a retiree shift up to $210,000 of balance out of the RMD calculation and defer payments to age 85. The carved-out dollars do not appear in the divisor math, lowering every RMD between 73 and 85 and reducing IRMAA exposure during the highest-premium Medicare years.

The action item before any of this: pull the December 31 balance, run the divisor, and check whether the resulting MAGI clears $109,000. If it does, the IRMAA letter is already in the mail two years from now, and the planning window for conversions is the time between today and the first RMD year. Waiting until 73 to model this is waiting too long.