Medicare IRMAA and Roth Conversion Planning

A Roth conversion executed two years before you enroll in Medicare can push your modified adjusted gross income (MAGI) above the threshold that triggers Income-Related Monthly Adjustment Amounts (IRMAA)—higher premiums for Part B, Part D, and other benefits. Sizing a conversion to stay below these cliffs requires understanding both the tax consequences and the Medicare income look-back window.

What IRMAA Is and Why It Matters

Income-Related Monthly Adjustment Amounts are surcharges added to your Medicare Part B (physician coverage) and Part D (prescription drug) premiums when your income exceeds a threshold. Unlike traditional Medicare premiums, which are flat across all beneficiaries, IRMAA creates a direct tax on higher income in retirement. For many retirees, IRMAA premiums exceed standard Medicare premiums by hundreds of dollars per month.

IRMAA applies based on your Modified Adjusted Gross Income (MAGI) from two years before you enroll. If you enroll in Medicare at age 65, the Social Security Administration (SSA) looks at your MAGI from age 63. This is the key: a Roth conversion at age 63 immediately affects the income SSA uses to calculate your IRMAA premium for the entire first year you receive Medicare benefits.

The Income Thresholds and Brackets

As of 2024, IRMAA applies to individuals with MAGI above $97,000 (single) or $194,000 (married filing jointly). The income thresholds are indexed annually for inflation. Above the initial threshold, your premium surcharge increases in five brackets. A single filer with $120,000 in MAGI pays higher premiums than one with $105,000, and the curve accelerates at higher income levels.

For Part B, the maximum surcharge can exceed $300 per month for the highest earners. Part D surcharges are typically smaller, but they stack on top. Combined, IRMAA can add $500+ per month to your Medicare costs for a year or longer, depending on when SSA recalculates based on updated tax returns.

The brackets are income-based, not age-based. You face the same surcharge structure whether you enroll at 65 or 70. The income measure is always MAGI from two years prior.

The Roth Conversion Problem

A Roth conversion converts funds from a traditional IRA (or other pre-tax retirement account) to a Roth IRA by paying income tax on the conversion amount. This is an optional event—the retiree chooses the timing and amount—and the amount converted is added to taxable income in the year of conversion.

If you perform a Roth conversion at age 63, that conversion amount is part of your MAGI for that tax year. When you enroll in Medicare at 65, SSA will look back two years and see the elevated MAGI. You will pay higher Medicare premiums for all of 2025 and potentially 2026, depending on when SSA recalculates.

Example: A single retiree with no other income performs a $100,000 Roth conversion at age 63. Her MAGI for that year is now $100,000—above the ~$97,000 IRMAA threshold. At Medicare enrollment (age 65), SSA calculates her premiums based on that $100,000 and assigns her to a higher IRMAA bracket. She pays the surcharge for the first year, even though her actual income in that year may be far lower.

The Two-Year Look-Back Window

The IRMAA look-back creates a planning opportunity if you understand the timing. Income reported in your tax return for year N affects your Medicare premiums two years later, in year N+2. This means:

• A Roth conversion at age 63 (year 1) affects IRMAA at age 65 (year 3).
• A conversion at age 64 (year 2) affects IRMAA at age 66 (year 4).
• A conversion before age 63 does not affect your age-65 Medicare IRMAA at all.

Conversely, if you enroll in Medicare at 65, SSA pulls income from age 63. Any high-income events or one-time gains at age 63 or 64 will echo forward. A well-timed capital gain or bonus at age 63 will push you into a higher IRMAA bracket at 65.

Sizing Conversions to Avoid IRMAA Cliffs

The threshold-based structure of IRMAA creates sharp income cliffs. Crossing the IRMAA threshold by even $1 can trigger a full tier of premium increases. This is why retirees contemplating Roth conversions in the two years before Medicare enrollment often calculate a “safe” conversion amount—large enough to be worthwhile but small enough to stay below or just enter the first IRMAA bracket.

For a single filer, a safe conversion might be capped at an amount that keeps MAGI just at or slightly above the initial IRMAA threshold. This avoids the worst of the surcharges while still allowing some pre-tax-to-Roth conversion. For a married couple, the thresholds are higher, offering more room to maneuver.

A retiree with multiple income sources must factor them all in: Social Security benefits (which count toward IRMAA MAGI), pension income, capital gains from sales, and traditional IRA or 401(k) distributions. The goal is to estimate total MAGI in the look-back year and size a conversion to stay below the cliff or acceptably within a higher bracket.

The Trade-Off: Roth Benefits vs. IRMAA Costs

The reason Roth conversions appeal to retirees despite the IRMAA risk is that they provide long-term tax savings. A Roth IRA grows tax-free, and qualified distributions are not subject to federal income tax or IRMAA. Over decades, this can offset the short-term IRMAA surcharge triggered by the conversion itself.

The calculus depends on:

• The size of the conversion (larger conversions trigger larger premiums).
• The marginal tax bracket in the conversion year (if you’re in a high bracket, the conversion cost is high).
• Your life expectancy and expected growth rate on the converted assets (longer horizons favor Roth).
• Your expected retirement income and IRMAA exposure in future years (if you expect to be in the IRMAA zone anyway, a conversion may be cheaper than you think).

A retiree who will eventually have substantial required minimum distributions from traditional IRAs or a large portfolio of taxable investment income might find that a Roth conversion before Medicare enrollment, though costly in IRMAA, saves money overall because it shrinks future IRMAA exposure.

Provisional and Deemed Income

The IRMAA calculation has subtleties. Some income sources have special treatment. For instance, Social Security income only partially counts toward IRMAA MAGI (50% of benefits, in most cases). Roth conversion amounts count fully.

If you do a Roth conversion and later decide to undo it (a recharacterization), the reversal must occur within the same tax year or by the tax filing deadline, and it requires a separate filing. Once the conversion is finalized, the income is locked in for IRMAA purposes.

Managing IRMAA: The Long View

For high-income retirees, IRMAA is a structural cost of retirement, not just a tax issue. Planning involves not only Roth conversions but also careful management of capital gains, dividend income, and retirement account distributions. Some retirees intentionally “bunch” income in certain years to spread the IRMAA hit across multiple years, or they defer discretionary income to years when other income is lower.

Medicare itself also allows beneficiaries to request a recalculation of IRMAA if their income declines during a calendar year (due to retirement, loss of income, or divorce). This provides a safety valve if unexpected circumstances change your income mid-year.

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