Roth Conversion Strategy: How to Find and Use Your Window

What Creates the Conversion Window

A Roth conversion moves money from a traditional (pre-tax) IRA or 401(k) to a Roth IRA. You pay income tax now; future growth and withdrawals are tax-free.

The window opens when employment income ends (retirement) and closes when mandatory taxable income begins (Social Security, RMDs, pension). During this gap — often 5 to 15 years — taxable income drops to its lowest point in decades.

When I sat down with clients in their first year of retirement, their W-2 income was gone, Social Security hadn't started, and RMDs were years away. Many could fill the 22% bracket — or even the 12% bracket — with Roth conversions that would have been in the 32%+ bracket just a year earlier.

How to Calculate What to Convert Each Year

The target conversion amount is the amount that fills your current tax bracket without crossing into the next one.

Example for a married couple with $40,000 of other taxable income in 2025: The 22% bracket begins at approximately $96,950 (MFJ). Converting up to $56,950 keeps everything in the 10-22% range.

But three factors can shift this calculation:

1. Medicare IRMAA: Roth conversions increase MAGI, which determines Medicare Part B/D premiums two years later. Crossing an IRMAA threshold can add $600-$7,400 per year in premiums. 2. Capital gains tax thresholds: A large conversion can push long-term capital gains from 0% to 15%. 3. Social Security taxation: Once provisional income exceeds $44,000 (MFJ), up to 85% of Social Security becomes taxable — conversions can push you through this threshold.

A full analysis accounts for all three.

What SECURE 2.0 Changed About the Window

SECURE 2.0 (2022) extended the Roth conversion window in two ways:

1. RMD age increases: Born 1951-1959, RMDs start at 73. Born 1960+, RMDs start at 75. Each year of delay is a year of conversion opportunity.

2. Roth 401(k) RMD elimination: As of 2024, Roth 401(k)s no longer have RMDs. This makes Roth accounts more valuable as estate vehicles — money can compound indefinitely without forced distributions.

The inherited IRA 10-year rule (SECURE Act 2019) adds another dimension: heirs must deplete inherited traditional IRAs within 10 years, often at their peak earning years and rates. Converting to Roth before death shifts the tax to your lower-rate years instead.

Lifetime Tax Comparison: The Actual Numbers

The way to evaluate a Roth conversion strategy is to project lifetime federal taxes under two scenarios: no conversions (relying entirely on RMDs) versus a conversion strategy during the window.

For a household with $800,000 in traditional IRA assets at age 62, converting $50,000 per year for 10 years during the window (paying tax at roughly 20-22%) versus taking RMDs starting at 73 (likely at 24-32% as the balance grows) can show $80,000-$150,000 in lifetime tax savings in many analyses.

Note that this varies enormously based on account balance, other income, and life expectancy. The analysis should model your specific situation rather than applying rules of thumb.