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

"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."

"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."

A 73-year-old with a $2.5 million traditional 401(k) must take a first required minimum distribution of about $94,340, calculated by dividing the prior year-end balance by 26.5. The distribution is ordinary income and stacks with Social Security, where up to 85% of benefits can become taxable at this income level. After applying the 2026 standard deduction for single filers age 65 and older, taxable income remains high, placing the retiree in the 22% federal bracket. Medicare Part B and Part D premiums increase at MAGI thresholds using a two-year lookback, creating IRMAA surcharges. Combined effects can raise the effective marginal rate on additional RMD dollars toward 40%. Inflation and interest-rate conditions can further worsen the tax impact.

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