IRMAA (Income-Related Monthly Adjustment Amount)
What IRMAA is
IRMAA (Income-Related Monthly Adjustment Amount) is a Medicare premium surcharge applied to Part B (medical insurance) and Part D (prescription drug coverage) for beneficiaries whose Modified Adjusted Gross Income (MAGI) exceeds specific thresholds.
The surcharge is means-tested and cliff-structured — not phased-in. Crossing a threshold by $1 of income triggers the full surcharge for that bracket, not a proportional increase. This makes IRMAA one of the most important and least-discussed variables in retirement income planning.
2026 IRMAA thresholds (approximate)
| MAGI (Individual) | MAGI (Married Filing Jointly) | Part B monthly premium | Part D monthly surcharge |
|---|---|---|---|
| Up to $103,000 | Up to $206,000 | $185/mo (standard) | $0 |
| $103,001 - $129,000 | $206,001 - $258,000 | $259/mo | $13/mo |
| $129,001 - $161,000 | $258,001 - $322,000 | $370/mo | $34/mo |
| $161,001 - $193,000 | $322,001 - $386,000 | $481/mo | $55/mo |
| $193,001 - $500,000 | $386,001 - $750,000 | $591/mo | $76/mo |
| Above $500,000 | Above $750,000 | $628/mo | $82/mo |
Thresholds are indexed to inflation. Verify current values at cms.gov.
Why IRMAA matters for Roth conversion planning
The cliff structure means a Roth conversion that pushes your MAGI from $205,000 to $207,000 (for a married couple) triggers the first IRMAA tier — adding approximately $74/month per person in Part B surcharges ($888/year per person, $1,776/year for the couple) plus Part D surcharges.
A Roth conversion of $50,000 at the 22% tax bracket costs $11,000 in income tax. If that conversion also triggers the first IRMAA tier, it adds another $1,776+ in Medicare premiums — effectively raising the true tax rate on that conversion.
Boldin PlannerPlus models the IRMAA cliff interaction with Roth conversions explicitly. This is one of the primary reasons Boldin is the recommended tool for pre-retirees and high earners doing Roth conversion planning.
Two-year look-back rule
IRMAA is calculated based on MAGI from 2 years prior. Your 2026 Medicare premium is based on your 2024 MAGI. This means a high-income year (RSU vest, Roth conversion, business sale) taken in 2024 triggers IRMAA in 2026 — and there is a formal appeal process if your income situation has changed materially (life-changing event appeal).
If you believe your IRMAA surcharge is incorrect (income dropped significantly), file an SSA-44 form with the Social Security Administration.
Primary sources
- CMS IRMAA thresholds and Part B premium — official CMS page
- SSA.gov IRMAA appeal process — Form SSA-44
- IRS Publication 590-B — IRA distribution rules that affect MAGI