Will a Roth conversion raise my Medicare premium?
How Medicare premiums and income are connected
Medicare charges higher Part B and Part D premiums to higher-income households through a surcharge officially called IRMAA (Income-Related Monthly Adjustment Amount). Two features make it dangerous for Roth conversion planning:
- It's a cliff, not a ramp. Crossing a threshold by even $1 triggers the full surcharge for that level, for the entire year, for each spouse enrolled in Medicare.
- It looks back two years. Your 2026 premium is set by your 2024 tax return. A conversion you do this December quietly sets a premium bill that arrives two Januaries from now.
The 2026 IRMAA thresholds
| Level | Single MAGI | Married filing jointly MAGI | Approx. added cost per person per year* |
|---|---|---|---|
| Base | Under $109,000 | Under $218,000 | $0 |
| Level 1 | $109,000+ | $218,000+ | ≈ $1,148 |
| Level 2 | $137,000+ | $274,000+ | ≈ $2,885 |
| Level 3 | $171,000+ | $342,000+ | ≈ $4,620 |
| Level 4 | $205,000+ | $410,000+ | ≈ $6,356 |
| Level 5 | $500,000+ | $750,000+ | ≈ $6,908 |
*Part B + Part D surcharge above the base premium, per enrolled person. A married couple both on Medicare pays roughly double these amounts. Figures use 2026 premium schedules.
Concretely: a couple with $217,900 of MAGI who converts $10,000 more crosses Level 1 and adds roughly $2,300 for the year in premiums (both spouses), a 23% "phantom tax" on that last conversion dollar, on top of income tax.
How conversion size interacts with the line
- Start from MAGI, not taxable income. For IRMAA, MAGI is your adjusted gross income plus tax-exempt interest. A conversion amount adds dollar-for-dollar.
- Find your headroom. Next threshold minus your projected MAGI is the amount that would reach the next threshold in this model.
- Crossing is a comparison, not an instruction. Sometimes a household compares absorbing one year of surcharge against moving a large amount out of a pre-tax IRA. The point is seeing the tradeoff, not being told which side to pick.
- Mind the deadline. Roth conversions count in the calendar year they're executed, December 31, not tax day.
The interaction people miss: conversions raise more than premiums
The same extra income can also pull more of your Social Security into taxation and phase out the $6,000 senior deduction at 6 cents per dollar, so the true marginal cost of a conversion dollar can be far above your bracket. That's why sizing a conversion by "staying in the 22% bracket" alone routinely misfires.
See this computed from your own tax return. The free check takes five minutes, runs in your browser, and shows your real marginal rate, Medicare headroom, and conversion stops to compare, no account needed.
Run my free check →Common questions
Does a Roth conversion count toward IRMAA income?
Yes. A conversion adds to your adjusted gross income dollar-for-dollar, and IRMAA is based on MAGI (AGI plus tax-exempt interest) from two years prior.
If I cross an IRMAA threshold by $1, what happens?
You pay the full surcharge for that level for the entire year, there is no proration. For a married couple both on Medicare, crossing the first 2026 threshold costs roughly $2,300 for the year.
Can I undo a conversion if I crossed a threshold?
No. Recharacterization of Roth conversions was eliminated in 2018. Conversions are permanent, which is why sizing them against the thresholds beforehand matters.
Do IRMAA thresholds change each year?
Yes, they're inflation-adjusted annually. The figures above are the 2026 thresholds; re-check before each year's conversion decision.