A 56-Year-Old Couple With $3.6M in 401(k)s Discovers $24,000 Annual Tax Leak They Can Plug
Holding $500,000 in taxable bonds inside a brokerage account costs this couple roughly $7,000 annually in unnecessary federal and state taxes.
A SECURE 2.0 rule effective January 2026 requires earners over $150,000 to route all age-50 catch-up contributions into a Roth 401(k).
Their $2.6M traditional 401(k) could hit $5.9M by age 73, forcing $220,000+ RMDs that trigger Social Security taxes and Medicare surcharges.
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A dual-income couple in their mid-50s walked into a fee-only planner's office last spring with a printout that looked enviable: $3.6 million spread across two traditional 401(k)s, a joint brokerage account, and a pair of small Roth IRAs. They were maxing every contribution, both employers matched generously, and they planned to stop working at 62. The planner spent an hour on the statements and handed back a number they had not expected: roughly $24,000 a year in federal and state tax friction that the portfolio did not need to be paying. All of it came down to geography, with no need to earn less, save more, or take on additional risk.
The story tracks closely with the kind of post that lands weekly on the Bogleheads forum and the Reddit personal finance threads: high earners with seven-figure balances who assumed maxing the plan was enough, only to discover the IRS was quietly clipping the compounding.
Two mistakes account for almost the entire leak. The first is asset location. The couple holds roughly $500,000 in taxable bonds and bond funds inside their joint brokerage, throwing off interest income at a 10-year Treasury yield environment near 4.56%. That is around $22,500 of fully taxable interest landing on a return where their combined household income puts them in the 24% federal bracket (incomes over $211,400 for joint filers in 2026). Add state tax and the bond sleeve alone is donating close to $7,000 a year that would disappear if those bonds sat inside the 401(k) instead.
The second is what fills the brokerage now: actively managed equity funds with 40% to 70% turnover. Those funds spit out short-term gains and non-qualified distributions every December. On the couple's roughly $300,000 in active equity holdings, the annual phantom tax bill runs another $5,000 to $8,000 versus a broad index ETF that distributes almost nothing. Stack in the missed opportunity to harvest losses during the rate-driven drawdowns of the past year (the 10-year yield swung from 3.97% in February to 4.67% in May) and the leakage clears $20,000 comfortably before the SECURE 2.0 catch-up wrinkle is even considered.
Both spouses earned more than $150,000 in 2025, which under the rule that took effect January 1, 2026 means every dollar of their age-50 catch-up must now be deposited into a Roth 401(k). The standard cap stays at $24,500, with an additional $8,000 catch-up per spouse. The couple had been treating $16,000 of combined catch-ups as pretax deferrals. They are not anymore. The lost current deduction is real (roughly $3,800 at the 24% rate) but the Roth dollars compound tax-free for the next 30 years, which flips the math in their favor if they live past 70. The trap is operational: payroll has to be told, and at many plans the default still routes catch-ups pretax until the participant changes the election.
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The looming issue is what happens in 2042, when the older spouse hits age 73 and required minimum distributions begin. A traditional 401(k) balance compounding at 6% from $2.6 million today reaches roughly $5.9 million by then. The first RMD alone runs north of $220,000, stacked on top of Social Security. That is the income level where 85% of benefits become taxable and IRMAA Medicare surcharges add $70 to $400+ per person per month. Every dollar of Roth conversion executed in the 24% bracket between 56 and 70 is a dollar that never appears in that RMD calculation.
Swap the geography. Move the entire fixed-income allocation inside the 401(k) and replace it in the brokerage with broad equity index ETFs. The mechanical change recaptures the largest single piece of the $24,000.
Reset the catch-up election. Confirm with payroll that the $8,000 catch-up is routing to the Roth side. Default settings are the silent failure point under the new rule.
Map a 14-year Roth conversion ladder. Fill the top of the 24% bracket each year between now and the first RMD. With the 2026 standard deduction at $32,200 for joint filers and brackets indexed to a Core PCE running at the 90.9th historical percentile, conversion capacity is wider than it looks.
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