Why Medicare IRMAA uses a two-year lookback (and which return year matters)
See the lane on the return Medicare is already using. Filing status and MAGI. Two questions. No account. Nothing uploaded. Not a bill.
Run the free checkThe mechanic: a return from two years earlier
Social Security does not set the income-related premium from this month's paycheck. It uses modified adjusted gross income (MAGI) from the latest processed federal return. That return is typically two years before the premium year. The official description is on SSA's Medicare premiums page.
These pairs name the calendar. They do not say whether any household is under or over a line.
| Tax return year (MAGI) | Premium year that return can set |
|---|---|
| 2024 | 2026 |
| 2025 | 2027 |
| 2026 | 2028 |
The first published 2026 Part B line, from the CMS fact sheet of November 14, 2025, is 2024 MAGI above $109,000 (single) or $218,000 (married filing jointly). Later tiers, and what IRMAA is, live on What is IRMAA? MAGI on this page means Form 1040 line 11 plus line 2a. See What is MAGI for Medicare?
The mix-up: this year's income is not this year's Part B
A common map puts this year's Roth conversion, or this year's required minimum distribution, onto this year's Part B premium. The calendars do not line up that way.
| What landed in income | Return year | Premium year it can affect | Premium year it does not reset |
|---|---|---|---|
| Roth conversion or RMD in 2026 | 2026 | 2028 | 2026 (already tied to the 2024 return) |
| Income already on the 2024 return | 2024 | 2026 | 2028 |
| Income on the 2025 return | 2025 | 2027 | 2026 |
A 2026 conversion is a 2026 MAGI event. The 2026 Part B premium is already looking at 2024. This page does not say whether to convert, and it does not calculate a withdrawal. Required withdrawals have their own age rules on what age RMDs start, and a December 31 processing clock on the RMD deadline checklist. The custodian clock for a same-year conversion is on the Roth conversion December 31 deadline. The custodian clock for a qualified charitable distribution is on the QCD deadline page. That page does not say whether to give. How a conversion can meet a line two years later is on Roth conversions and the Medicare premium.
What the free check does
The free check asks two things: whether the household is married filing jointly, and MAGI from the tax return Medicare is using (line 11 plus line 2a). It marks that figure UNDER or OVER the published first Part B line. It is not a bill. It is not a premium notice. It is not advice. It does not assign a tier for a later premium year, and it does not promise what a household will owe.
CMS does not publish a near tier. The free check stays UNDER or OVER.
Free, two questions. The free check names which return year sets this year's premium and whether that return is over the first published 2026 Part B line. It does not calculate a conversion. It does not say whether to take an RMD. It is not the $99/year household board.
Run the free checkRelated reading
Common questions
Which tax return sets a Medicare premium year?
Usually the federal return from two years earlier. 2024 MAGI is what SSA generally uses for 2026 premiums. 2025 maps to 2027. 2026 maps to 2028. SSA uses the latest return the IRS has already processed. Source: Medicare premiums for higher-income beneficiaries.
Why does Medicare IRMAA use a two-year lookback?
SSA sets the year's Part B and Part D income-related amounts from MAGI already on file, typically the return from two years before the premium year. It is not a reading of this month's paycheck.
Does income this year change this year's Part B premium?
Not through the ordinary lookback. Income in 2026 is reported on the 2026 return, which is the return used for the 2028 premium year. The 2026 premium is already tied to the 2024 return. A listed life-changing event is a separate SSA-44 process. This site does not file that form. Official door: ssa.gov/medicare/lower-irmaa.
Educational only. Not tax, legal, or Medicare advice. Confirm the year pair and the dollar lines on the CMS 2026 Part B fact sheet and the SSA Medicare premiums page. MAGI here is Form 1040 line 11 plus line 2a, as described in the IRS Form 1040 instructions. Review the notice SSA mailed with a CPA before treating any year pair as this household's bill.