Roth Conversion Window: Why a 68-Year-Old With $1.5M Has Five Years to Move $600K

Here is the setup: a 68-year-old couple has $1.5 million sitting in traditional IRAs, a pension, and Social Security. Household income runs around $85,000 a year, and the IRA has not been touched. Life is comfortable. The temptation is to leave the IRA alone and let it compound.

That instinct is expensive. At 73, required minimum distributions begin, and the IRS stops caring whether the money is needed. On a $1.5 million balance, first-year RMDs land near $57,000 and grow every year after. That income stacks on top of the pension and Social Security, pushes the couple into higher brackets, and triggers Medicare surcharges (IRMAA) that follow them for life. The five tax years between 68 and 72 are critical precisely because they offer a window to act before those forced withdrawals begin.

Why the Pre-RMD Window Is So Valuable

Right now, this couple sits in the 12% bracket. The 2026 standard deduction for married filing jointly is $32,200, and the 22% bracket runs from $100,800 to $211,400 of taxable income. The 24% bracket extends all the way to $403,550, and the 32% rate does not kick in until income exceeds that threshold. There is enormous headroom above $85,000 of ordinary income before hitting the 32% cliff. One additional tailwind worth noting: the One Big Beautiful Bill Act, signed in July 2025, made the seven-bracket structure permanent and introduced a new $6,000 bonus deduction for taxpayers age 65 and older. Married couples where both spouses qualify can claim up to $12,000 combined. The deduction phases out above $150,000 of modified AGI for joint filers and disappears entirely at $250,000, and it is available for tax years 2025 through 2028 only.

Roth conversions fill that headroom on purpose. Move dollars from the traditional IRA into a Roth, pay ordinary income tax on the amount moved, and the balance grows tax-free forever with no future RMD. According to Fidelity’s Q1 2026 retirement analysis, the average Baby Boomer IRA balance stands at $257,002, meaning a $1.5 million pre-tax balance is well above the norm and even more exposed to future bracket creep. That same Fidelity analysis found that Roth conversion transactions rose 41% year over year in Q1 2026, a sign that more retirees are acting on this strategy. Average IRA balances dipped modestly quarter-over-quarter in Q1 due to market volatility, but the one-year and five-year trends both remain positive.

Converting roughly $120,000 per year for five years moves about $600,000 into the Roth. Each conversion year, taxable income lands somewhere in the 22% to 24% zone. The alternative is doing nothing and letting a growing IRA push RMDs into 32% or 35% territory a decade from now, especially after one spouse dies and the survivor files single, where those same brackets kick in at roughly half the income.

The payoff has three layers:

1. Smaller RMD base at 73. Halving the pre-tax balance roughly halves lifetime forced income, which keeps the couple out of higher brackets and out of the top IRMAA tiers.
2. Widow protection. Single brackets are punishing. A surviving spouse with a large traditional IRA can jump two brackets overnight for the same standard of living. A Roth balance sidesteps that entirely.
3. Cleaner inheritance. Under the 10-year rule, heirs must drain an inherited IRA within a decade and pay taxes on every dollar. An inherited Roth drains tax-free.

The Real Tradeoffs

Two caveats matter. First, every conversion year likely bumps modified adjusted gross income above the IRMAA thresholds, adding roughly a 1% to 2% drag on the converted amount through higher Medicare premiums two years later. That surcharge is real and needs to be modeled, but it is almost always smaller than the bracket arbitrage the conversion captures. Conversion income can also push the couple above the $150,000 MAGI threshold where the OBBBA senior deduction begins to phase out at 6 cents for every dollar of excess, so the annual conversion amount needs to account for that interaction as well.

Second, Roth conversions cannot be undone. Convert too much in a single year, and there is no take-back. Converting without projecting future brackets, Social Security taxation, and IRMAA tiers is the most common way people over-convert and end up with a larger tax bill than if they had done nothing.

Opportunity cost deserves a mention. With the 10-year Treasury yielding roughly 5.2% and the 30-year at around 5.5%, the tax dollars paid on a conversion could otherwise sit in safe bonds earning competitive returns. Even so, tax-free compounding inside a Roth generally wins over a 15- to 25-year horizon when the conversion rate is meaningfully below the expected withdrawal rate.

What to Do First

Two concrete steps for anyone recognizing themselves in this scenario:

1. Model the full bracket ladder before touching a dollar. Include the pension, Social Security taxation (the 2026 COLA was 2.8%, so benefits grow every year), projected RMDs at 73, IRMAA tiers, and the OBBBA senior deduction and its phase-out. Then size the annual conversion to fill the 22% or 24% bracket without spilling into 32%.
2. Avoid the all-at-once mistake. Converting $600,000 in a single year would blow through the 32% and 35% brackets and trigger the highest IRMAA tier. Spread across five tax years, the same dollars move at a far lower marginal rate.

This is a situation where a fee-only advisor pays for themselves in the first meeting. With a $1.5 million pre-tax balance, a five-year conversion plan, IRMAA surcharges to sequence, and a temporary senior deduction expiring after 2028 to preserve, the difference between a rigorous multi-year projection and a back-of-the-envelope estimate can easily reach six figures over a lifetime.

Editor’s note: This article corrects the average Baby Boomer IRA balance to $257,002 based on Fidelity’s Q1 2026 retirement analysis, updates Treasury yield figures to reflect late September 2026 market levels (10-year at approximately 5.2%, 30-year at approximately 5.5%), and adds detail on the OBBBA senior deduction’s $12,000 combined maximum for qualifying couples and its 2025-through-2028 sunset.

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