Roth Conversions and IRMAA: The Medicare Premium Cliff Most Retirees Miss

Most retirees doing Roth conversions are watching their federal income tax bracket. They are not watching IRMAA. That oversight can turn a smart tax move into a four-figure annual penalty that runs for years.

What IRMAA Is and Why It Catches People Off Guard

IRMAA stands for Income-Related Monthly Adjustment Amount. It is a Medicare surcharge applied to Part B (medical coverage) and Part D (prescription drug coverage) premiums when your income exceeds certain thresholds. It is not a penalty for doing something wrong. It is simply the government's way of means-testing Medicare.

The part that trips retirees up: Medicare does not look at your income this year. It looks at your Modified Adjusted Gross Income (MAGI) from two years prior. If you retire at 63, convert a large chunk of your IRA in 2025, and enroll in Medicare at 65, the 2025 conversion shows up in your 2027 premiums. You may have entirely forgotten about that conversion by the time the bill arrives.

For 2024, the standard Medicare Part B premium is $174.70 per month. Once your MAGI crosses the first IRMAA threshold ($103,000 for single filers, $206,000 for married filing jointly), that premium jumps to $244.60. Cross the next tier, and it climbs again. At the top tier (MAGI above $500,000 single / $750,000 MFJ), a married couple pays over $1,000 per month combined just for Part B, before Part D surcharges are added. Those are five distinct cliff edges, and each one is a hard step, not a slope.

The Rules, the Tiers, and the Real Dollar Exposure

Here is where the math gets uncomfortable. IRMAA tiers for 2024 (based on 2022 MAGI) are roughly as follows for single filers:

• Tier 1: MAGI $103,001 to $129,000, adds $69.90/month to Part B
• Tier 2: MAGI $129,001 to $161,000, adds $174.70/month
• Tier 3: MAGI $161,001 to $193,000, adds $279.50/month
• Tier 4: MAGI $193,001 to $500,000, adds $384.30/month
• Tier 5: MAGI above $500,000, adds $419.30/month

Each tier also carries a Part D surcharge ranging from roughly $12 to $81 per month. For a married couple, every dollar figure doubles.

The critical structure to understand: these are cliff thresholds, not brackets. One dollar of extra income does not nudge you a little higher. It drops you into the next tier entirely. A Roth conversion that pushes your MAGI from $128,500 to $129,500 costs you an extra $174.70 per month, or $2,096 per year, for a one-dollar overage. That is the cliff.

There is also a two-year lag to manage in both directions. If you can appeal an IRMAA surcharge because of a qualifying life event (retirement, divorce, death of a spouse), you can request a recalculation using more recent income. Form SSA-44 handles this. But if the higher income came from a deliberate Roth conversion, the appeal will not succeed. The income was real and reported.

A Worked Example: The $40K Conversion That Cost More Than It Should

Suppose a married couple, both 66, has a combined MAGI of $195,000 in 2025 before any Roth conversion. They are in the third IRMAA tier already. Their financial advisor suggests a $40,000 Roth conversion to reduce future RMDs.

That conversion lifts MAGI to $235,000, pushing them into the fourth tier. The jump from Tier 3 to Tier 4 adds $210 per month per person in Part B surcharges, plus roughly $20 more per person in Part D. For a couple, that is $460 per month extra, or $5,520 per year, for two years (because Medicare will see that 2025 income in both 2027 and only recalibrate when 2026 MAGI is reported). The two-year cost of crossing that single tier: over $11,000.

The alternative approach: spread that $40,000 over three to four years instead of one. Converting roughly $12,000 to $13,000 per year keeps the couple inside Tier 3 (assuming their base MAGI stays near $195,000 and no other income spikes). The Roth conversion still happens. The IRA still shrinks. Future RMDs are still reduced. But the IRMAA exposure never moves.

This is exactly the kind of sequencing work that belongs in the Harvest stage of a retirement plan, where tax-aware withdrawal timing determines how much of your money you actually keep. If you want to understand the broader conversion strategy this fits into, the parent piece, Roth Conversion: A Practical Guide for High Earners and Pre-Retirees, covers the full bracket math, the 5-year rule, and ACA premium interactions that also depend on MAGI.

How This Connects to the Soil Layer

IRMAA is a tax architecture problem, not an investment problem. It belongs squarely in what the Sporos Doctrine calls the Soil layer, the part of the plan that builds the structure around which every investment decision runs. Getting the Roth conversion amount right in any given year is less about return projections and more about knowing where your MAGI lands relative to five specific lines on a government table.

The grafting work here is precise: you are converting just enough to reduce the long-term tax burden without triggering a premium cliff that erodes the near-term benefit. A single-year conversion that saves $4,000 in future income taxes but triggers $11,000 in IRMAA surcharges is not a win.

Frequently Asked Questions

Does a Roth conversion always count toward IRMAA?

Yes. A Roth conversion is included in MAGI because it is treated as ordinary income in the year you convert. There is no exclusion for conversions done inside traditional IRAs.

Can I appeal an IRMAA surcharge if it was caused by a Roth conversion?

Generally no. The SSA-44 life event appeal applies to income reductions from specific qualifying events like retirement or divorce. A Roth conversion is a voluntary transaction and does not qualify for reconsideration.

What if I have already retired and my income dropped significantly?

You can file SSA-44 if your income dropped due to a qualifying life event. If it dropped simply because you stopped working (and had no conversion), the lower income will naturally flow through to your premiums two years later. The two-year lag still applies.

How do I find out what IRMAA tier I am in for next year?

Medicare sets IRMAA tiers annually. Your income from two years prior (as reported to the IRS) determines your tier. You receive a determination letter from Social Security, and you can appeal within 60 days if the income data is wrong.

Do Roth IRA distributions in retirement count toward IRMAA?

No. Qualified distributions from a Roth IRA are not included in MAGI. This is one of the core long-term benefits of converting now: future distributions come out tax-free and do not push you into higher IRMAA tiers later.

Does IRMAA affect both spouses even if only one converts?

Yes, because IRMAA for married filing jointly uses combined MAGI. A conversion by one spouse lifts the household MAGI and can trigger surcharges for both.

What to Do Next

1. Pull your last two years of tax returns and note your MAGI. Compare it to the current IRMAA thresholds, which the SSA publishes annually, to understand how much conversion headroom you have.
2. Model the conversion amount that stays inside your current IRMAA tier rather than targeting a round number like $50,000 or $100,000.
3. If you are already receiving Medicare and received an IRMAA determination you believe is based on stale income, review SSA Form SSA-44 to understand your appeal options.
4. Coordinate your conversion sequencing with both your tax professional and your financial planner before year-end, since the MAGI calculation depends on every other income source landing as expected.

The information provided is for educational purposes only and does not constitute investment, legal, or tax advice. Tax law changes frequently — verify current rules before acting. Consult with qualified professionals for guidance specific to your situation.