Roth Conversions and IRMAA: A Strategic Guide to Minimizing Lifetime Taxes
Roth conversions are one of the most powerful tools in a retiree’s tax planning arsenal. But executed without care, they can trigger Medicare’s Income-Related Monthly Adjustment Amount—better known as IRMAA—adding thousands of dollars in annual surcharges to your Medicare premiums.
The key is timing. Convert too much in a single year, and you push your Modified Adjusted Gross Income (MAGI) over an IRMAA cliff. Convert too little, and you leave tax-deferred money sitting in accounts that will eventually force larger Required Minimum Distributions (RMDs), higher taxes, and potentially higher IRMAA charges down the road.
This post explores how to time Roth conversions strategically—balancing income tax brackets, IRMAA thresholds, and the long-term goal of minimizing lifetime taxes for you and your heirs.
What Is IRMAA and Why Does It Matter?
IRMAA is a surcharge on Medicare Part B and Part D premiums for higher-income beneficiaries. It affects roughly 7–8% of Medicare enrollees, and it operates on a cliff structure: exceeding a threshold by even one dollar triggers the full surcharge for that tier.
For 2026, IRMAA is determined by your 2024 MAGI—your Adjusted Gross Income plus any tax-exempt interest income. This two-year lookback is critical for planning. The income decisions you make today affect your Medicare premiums two years from now.
What counts toward MAGI for IRMAA? Wages, pensions, Social Security benefits, traditional IRA/401(k) distributions (including Roth conversions), capital gains, rental income, interest, dividends—and even tax-exempt municipal bond interest.
What does not count? Qualified Roth IRA withdrawals and HSA distributions for medical expenses.
How Roth Conversions Interact with IRMAA
A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA. You pay income tax on the converted amount in the year of conversion, but qualified Roth withdrawals are tax-free for life—and they do not count toward MAGI for IRMAA purposes.
Here’s the tension: the conversion itself increases your MAGI in the conversion year, which can trigger IRMAA surcharges two years later. But by reducing your traditional IRA balance, you reduce future RMDs, future taxable income, and future IRMAA exposure.
This is a classic short-term pain, long-term gain scenario. The question is how much pain to take in any given year.
The Roth Conversion “Sweet Spot” Framework
Effective Roth conversion planning requires you to look at three constraints simultaneously for each conversion year.
Constraint 1: Federal income tax brackets. You generally want to convert enough to “fill up” your current marginal tax bracket without pushing into the next one.
Constraint 2: IRMAA thresholds. Because IRMAA uses MAGI rather than taxable income, and because it operates on cliffs rather than gradual phase-ins, you need to calculate where your MAGI will land after adding the conversion amount. Staying just below an IRMAA threshold—even if it means converting less than a full tax bracket would allow—can be worth it.
Constraint 3: The two-year lookback. Your 2026 MAGI affects your 2028 IRMAA. You need to project not just this year’s tax picture, but what your Medicare costs will look like two years from now.
The sweet spot is the largest conversion amount that keeps you within an acceptable tax bracket and below the next IRMAA cliff—or, if you decide to accept a higher IRMAA tier, one where the total cost (tax plus two years of surcharges) is still lower than the lifetime tax savings from the conversion.
The Golden Window: When Timing Is Everything
The most valuable Roth conversion years tend to fall in specific life stages where income is naturally lower. Understanding these windows can save you tens or even hundreds of thousands of dollars in lifetime taxes.
Early Retirement Before Social Security (Ages 62–70)
If you retire before claiming Social Security, your taxable income may drop dramatically. This is often the single best opportunity for Roth conversions. Without wages and before Social Security benefits begin, you may have only modest pension income, dividends, or interest filling the lower tax brackets. You can convert significant amounts while staying in the 12% or 22% bracket—rates that are historically low and may not last.
After Retirement, Before Age 73 (RMD Age)
Even after claiming Social Security, the years before RMDs begin (currently age 73 for those born 1951–1959, and age 75 for those born 1960 or later) present an opportunity. Without forced distributions from traditional IRAs, you control how much taxable income you recognize. Each year you convert, you shrink the IRA balance that will eventually generate mandatory taxable distributions.
Years of Unusually Low Income
A down year in the market, a gap between jobs, or a year when deductions are unusually high can create a temporary low-income window. These are excellent years to accelerate conversions.
Before the Surviving Spouse Files as Single
This is the often-overlooked “widow’s penalty.” When one spouse dies, the surviving spouse must file as single the following year. Single filers face narrower tax brackets and lower IRMAA thresholds ($109,000 versus $218,000 for joint filers). If the surviving spouse inherits both spouses’ traditional IRAs, the RMDs can push them into much higher brackets. Converting while both spouses are alive and filing jointly provides more room under both tax brackets and IRMAA thresholds.
IRMAA-Aware Conversion: A Step-by-Step Process
Here’s how to calculate your optimal Roth conversion amount each year.
When It Makes Sense to Accept IRMAA
Avoiding IRMAA entirely is not always the right answer.
A married couple has $2 million in traditional IRAs. Their baseline MAGI is $180,000. They could convert $38,000 to stay under the $218,000 IRMAA threshold—or they could convert $94,000 to fill the 22% bracket.
The extra $56,000 conversion would trigger the first IRMAA tier, costing about $2,296 in additional annual premiums ($81.20 × 2 people × 12 months for Part B, plus $14.50 × 2 × 12 for Part D). But that $56,000, now in a Roth IRA, will never be taxed again. If it grows at 7% for 15 years, it becomes roughly $154,000 in tax-free money.
The IRMAA cost is a one-time premium increase; the tax savings compound for decades.
The math often favors accepting one tier of IRMAA to convert more. Where it usually does not make sense is jumping multiple IRMAA tiers, where the surcharges escalate rapidly, and the marginal tax rate on the additional conversion may be much higher.
Strategies to Complement Roth Conversions
Several other strategies work alongside Roth conversions to manage MAGI and minimize lifetime taxes.
Qualified Charitable Distributions (QCDs)
If you’re 70½ or older, you can direct up to $108,000 (2025 limit, indexed for inflation) from your IRA directly to charity. QCDs satisfy your RMD requirement but are excluded from MAGI entirely—reducing both your income tax and IRMAA exposure.
Tax-Loss Harvesting
Realizing capital losses in taxable accounts can offset gains and reduce MAGI, creating more room for Roth conversions.
Roth Contributions During Working Years
Contributing to a Roth 401(k) or Roth 403(b) while still employed means those dollars never enter the traditional IRA pipeline. For educators and public service professionals with access to 403(b) and 457(b) plans, directing some contributions to Roth options reduces future RMD pressure.
Health Savings Account (HSA) Contributions
If you’re still eligible for an HSA (before Medicare enrollment), maximizing contributions reduces current MAGI and creates a pool of tax-free medical funds in retirement.
Asset Location
Holding tax-inefficient investments (bonds, REITs) in tax-deferred accounts and tax-efficient investments (index funds, growth stocks) in Roth and taxable accounts can reduce the annual taxable income that limits your conversion capacity.
The Lifetime Tax Minimization Mindset
The overarching principle is this: you are not trying to minimize taxes in any single year. You are trying to minimize the total taxes paid over your lifetime, and potentially your heirs’ lifetimes.
This requires a willingness to pay some taxes now at favorable rates to avoid paying more taxes later at higher rates. Consider the forces that can push future taxes higher: growing traditional IRA balances generate ever-larger RMDs; the loss of a spouse shifts you to less favorable single-filer brackets and lower IRMAA thresholds; potential future tax rate increases are always a possibility; and the SECURE Act eliminated the stretch IRA for most non-spouse beneficiaries, meaning your heirs must empty inherited traditional IRAs within 10 years, often at their peak earning years and highest marginal tax rates.
Roth conversions address all of these risks. The converted amount grows tax-free, is not subject to RMDs during the owner’s lifetime, does not affect IRMAA when withdrawn, and can be passed to heirs who receive the balance income-tax-free (though the 10-year distribution rule still applies).
Key Takeaways
Use IRMAA thresholds as guardrails, but don’t let IRMAA avoidance override the bigger picture of lifetime tax minimization. Convert late in the calendar year, when your income picture is clearest. Plan for the surviving spouse scenario, since the widow’s penalty can dramatically increase the tax burden on the surviving partner. And run the numbers annually, because your income, tax brackets, and IRMAA thresholds all change from year to year. Roth conversion planning is not a one-time decision. It’s an annual discipline that, done well, can save you and your family significant money over decades. Reach out to me on the contact page below to learn about whether Roth conversions are the right strategy for you.
Disclaimer: This post is for informational and educational purposes only and does not constitute personalized financial, tax, or legal advice. Consult with a qualified financial planner and tax professional before making Roth conversion decisions. Chris Reddick, CFP®, RICP®, EA, is the founder of Chris Reddick Financial Planning, LLC, a fee-only, advice-only financial planning firm in San Antonio, TX, specializing in retirement, investment, and tax planning for educators and public service professionals.
