Retired couples can withdraw up to $133,000 annually from a 401(k) before age 70 and stay within the 12% federal tax bracket.
Delaying Social Security from 62 to 70 boosts the monthly benefit by ~76%, delivering an inflation-linked 8% return no bond can match.
Over a 25-year retirement, this tax-bracket arbitrage strategy can save couples with $1.5 million in a 401(k) up to $300,000 in taxes.
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A 63-year-old couple with $1.5 million in a traditional 401(k) just retired. Their instinct is to claim Social Security as soon as possible and let the 401(k) keep compounding. That instinct will cost them six figures in lifetime taxes. The better play is the opposite: spend down the 401(k) aggressively between now and 70, and let Social Security grow untouched.
Reddit's r/financialindependence is full of variations on this question, usually framed as "why would I ever burn my tax-deferred account before touching Social Security?" The answer is a window most retirees never plan for: the tax valley between the last paycheck and the first required minimum distribution.
From roughly 62 to 73, a retired couple with no wages and no Social Security has almost no taxable income. Under the 2026 tables, a married couple filing jointly gets a $32,200 standard deduction, pays 10% on the next $24,800, and stays in the 12% bracket up to $100,800 of taxable income. Stack those together and this couple can pull roughly $133,000 a year from the 401(k) and never see a rate above 12%.
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Now compare that to what happens if they claim Social Security at 62 and leave the 401(k) alone. The account keeps compounding. At 73, RMDs kick in on a much larger balance. Social Security is already flowing. The two income streams stack on top of each other, up to 85% of the Social Security check becomes taxable, and the marginal bracket jumps to 22% or 24%. Layer in IRMAA surcharges on Medicare premiums (triggered on a two-year lookback once modified AGI crosses roughly $212,000 for a couple) and the effective marginal rate on the last dollar of an RMD can approach 40%.
Every year a retiree delays Social Security past full retirement age adds roughly 8% to the benefit, and claiming at 62 instead of full retirement age cuts the check by up to 30%. Delaying from 62 all the way to 70 lifts the monthly benefit by about 76%. That increase is inflation-adjusted every year through COLA, which came in at 2.8% for 2026.
The 10-year Treasury yields almost 5% today. Social Security effectively delivers an 8% real, inflation-linked, longevity-hedged return that no fixed-income instrument on the open market can match, and the "purchase price" is simply spending down other assets first.
Suppose our 63-year-old couple pulls $130,000 a year from the 401(k) for seven years. That's roughly $910,000 withdrawn at a blended federal rate near 10%. Meanwhile, the delayed Social Security benefit at 70 might run $60,000 a year for the higher earner instead of $34,000 at 62. When RMDs finally start at 73, the 401(k) is materially smaller, so the RMD is smaller, taxable Social Security stays lower, and IRMAA is easier to dodge.
The alternate path leaves a bigger 401(k) that forces a bigger RMD, taxed at 22% or 24%, on top of a permanently smaller Social Security check that is now 85% taxable. Over a 25-year retirement, the tax-bracket arbitrage alone is commonly worth $150,000 to $300,000 for balances in this range.
Map your tax valley. Build a year-by-year projection from today to age 75 showing wages, pensions, 401(k) withdrawals, Social Security, and RMDs. The goal is to fill the 12% bracket every year before 70 without spilling into 22%.
Model the Social Security break-even. Delaying to 70 typically breaks even in the early 80s. If both spouses are in average health, delaying the higher earner's benefit is almost always the correct call, since the survivor keeps the larger check.
Watch the IRMAA cliffs. Modified AGI is measured on a two-year lookback. A single dollar over a threshold triggers the full surcharge tier. If you're within $5,000 of a bracket, defer the last 401(k) withdrawal to January or offset it with a qualified charitable distribution once you turn 70½.
The retirees who win this game treat their 401(k) as the first bucket to spend and Social Security as the last. The tax code is quietly designed to reward exactly that order.
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