IRMAA 2026: Medicare Premium Surcharges by MAGI
How IRMAA brackets work for Part B and Part D, which year’s MAGI CMS uses, and why a Roth conversion can raise next year’s Medicare premiums.
Published 2026-03-10 · Updated 2026-07-20
IRMAA is not a tax on your Form 1040. It is an income-related monthly adjustment amount added to Medicare Part B and Part D premiums when your modified AGI from two years earlier crosses CMS brackets. For most people paying 2026 premiums, CMS looks at the 2024 tax return.
Brackets are filed by status (individual vs joint). Crossing a bracket is all-or-nothing for that tier—you do not pay a pro-rated surcharge for being $1 over the line. That cliff structure is why year-end capital gains, Roth conversions, and large IRA distributions deserve a second look if you are near a threshold.
What counts as MAGI for IRMAA
CMS starts from AGI and adds tax-exempt interest. Other adjustments can apply in edge cases; use the IRMAA notice definitions if you receive Form SSA-44 after a life-changing event.
Social Security benefits that were taxable on your return are already inside AGI. Tax-free municipal bond interest that never hit AGI can still push IRMAA MAGI higher.
Planning levers
If you are still working and covered by employer insurance, IRMAA may not matter yet—but the lookback means decisions today show up in premiums later. Spreading Roth conversions across years, harvesting gains carefully, and timing large asset sales can keep you under a bracket when Medicare enrollment is near.
Use the IRMAA calculator with the published 2026 CMS figures on this site. If your income fell because of retirement, divorce, or other qualifying events, check whether a new determination request is available rather than waiting two years for the lookback to catch up.
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Tax year 2026 · Last reviewed 2026-07-20 · Reviewed by US Tax Tools editorial · Methodology