Picture a single 73-year-old retiree sitting on $1.3 million in a traditional 401(k), drawing $36,000 a year in Social Security, and feeling reasonably set for retirement. 2026 is the year required minimum distributions begin, and the IRS just handed this saver a tax bill they did not budget for. The first-year cost across federal, state, and Medicare runs close to $19,800, and almost none of it shows up on a brokerage statement.
This scenario surfaces constantly in retirement forums: someone in their early 70s who deferred taxes diligently for 40 years discovers that the deferral was a loan, and the IRS is the lender calling it in.
The RMD Math, Line by Line
At age 73, the IRS Uniform Lifetime Table assigns a divisor of 26.5. A $1.3 million balance divided by that figure produces a mandatory withdrawal of $49,057. That number is non-negotiable. Missing it triggers a 25% excise tax on any shortfall, reduced to 10% only if corrected within a two-year window.
Layered on top, the RMD pushes provisional income high enough that 85% of the $36,000 Social Security benefit becomes taxable, adding roughly $30,600 to adjusted gross income. Total ordinary income lands near $85,000.
Deductions help, but only somewhat. A single filer who is 65 or older in 2026 claims the base standard deduction of $16,100, adds the senior additional amount of $2,050, and then stacks the new $6,000 senior bonus deduction available in full to any filer whose MAGI stays below $75,000. Those three layers together shelter $24,150 of income, leaving taxable income near $61,000.
What the Brackets Actually Take
For 2026, the One Big Beautiful Bill Act permanently extended the TCJA rate structure, and the IRS then applied inflation adjustments that widened the lowest brackets more than previous years. For a single filer, the 10% rate covers the first $12,400 of taxable income, the 12% rate runs from there to $50,400, and the 22% rate applies above $50,400.
Stacking those against $61,000 of taxable income: 10% on the first $12,400 equals $1,240, 12% on the next $38,000 equals $4,560, and 22% on the remaining $10,600 equals $2,332. Total federal liability comes in around $8,132.
That looks manageable until the rest of the cascade arrives. State income tax in most states adds another 3% to 6% on the same income. The 2026 IRMAA Medicare surcharge does not hit this filer yet because the first single-filer threshold starts at $109,000 in MAGI. The two-year lookback rule, though, means a single bad year (a home sale, a Roth conversion, or a larger RMD as the balance grows) can quietly add roughly $1,148 to annual Medicare costs the moment MAGI crosses that cliff in any future year. Roll federal, state, and the embedded cost of higher provisional income together, and the cumulative first-year hit settles near $19,800.
The Senior Bonus Cliff Nobody Talks About
The new $6,000 deduction phases out at 6 cents per dollar of MAGI above $75,000 for single filers and disappears entirely at $175,000. This retiree sits just below that line, which means a portfolio rebalance, a capital gain, or a larger withdrawal in any year between now and 2028 could shave or eliminate the deduction and quietly raise the effective marginal rate. Knowing where that cliff sits is worth real money, because the senior bonus provision expires after the 2028 tax year under current law.
Three Moves That Change the Outcome
- Roll the 401(k) to an IRA, then use a qualified charitable distribution to satisfy part of the RMD. Qualified charitable distributions of up to $111,000 per person in 2026 count toward the RMD but never enter AGI. For a retiree already giving to a church or charity, redirecting even $10,000 to $20,000 of the RMD this way lowers taxable Social Security, preserves the senior bonus deduction, and protects future IRMAA brackets. The strategy is especially potent in 2026 because the One Big Beautiful Bill Act introduced a new 0.5%-of-AGI floor on charitable itemized deductions, making the QCD route more tax-efficient than a cash gift for most standard-deduction filers. Note that 401(k) plans cannot make QCDs directly; an IRA rollover is the required first step.
- Do partial Roth conversions in the years before 73. A saver at 65 with the same balance who converted $30,000 to $50,000 annually at the 12% rate would have a smaller pre-tax balance, smaller RMDs, and a tax-free pool to draw from when IRMAA pressure builds. The window closes the moment RMDs begin, because the RMD itself must come out before any conversion in the same year.
- Smooth the bracket in the year before RMDs begin. At 72, voluntary withdrawals filling the 12% bracket (up to roughly $50,400 of taxable income for single filers in 2026) cost the same 12 cents on the dollar as the first slice of the first RMD, with no Social Security multiplier in play if benefits have been delayed. That kind of proactive drawdown can meaningfully shrink the balance subject to future mandatory distributions.
$1.3 million is plenty to retire on, provided the order in which the IRS, the SSA, and CMS take their cut gets the same attention as the portfolio itself.
Editor’s note: This article has been updated to reflect 2026 federal income tax bracket thresholds (10% through $12,400, 12% through $50,400 for single filers) per IRS Revenue Procedure 2025-32, replacing 2025 figures used in an earlier version. The updated bracket math produces a revised federal liability estimate of approximately $8,132, and the 2026 One Big Beautiful Bill Act context on the new 0.5%-of-AGI floor for charitable deductions has been added to the QCD section.
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