MAGI for IRMAA: what counts and how to calculate it

How do you calculate MAGI for IRMAA?

Open the Form 1040 for the year in question, read line 11, read line 2a, and add them. That is the entire calculation, and it comes straight from Social Security's operating manual (POMS HI 01101.010). There is no worksheet and no schedule.

To make it concrete, take a single filer's 2024 return with four income items: a $52,000 pension, a $30,000 withdrawal from a traditional IRA, $16,400 of taxable Social Security benefits, and a $7,000 realized capital gain. Those sum to an AGI of $105,400 on line 11. Line 2a shows $6,800 of municipal bond interest. Add the two lines: $105,400 plus $6,800 is a MAGI of $112,200. The AGI on its own sits below the $109,000 threshold; the MAGI does not. In 2026 this filer pays the first-tier surcharge, $81.20 per month on Part B plus $14.50 on Part D.

Strip out the bond interest and MAGI equals AGI at $105,400, below the line, with no surcharge at all. And for a filer old enough to make qualified charitable distributions, had $4,000 of that IRA withdrawal gone straight from the IRA to a charity as a QCD, line 11 would have read $101,400 and MAGI $108,200, under the threshold even with the bond interest still there. To test any other set of numbers against the tiers, see where your MAGI lands in the IRMAA calculator.

Is IRMAA based on AGI or MAGI?

MAGI, but the two are closer than the names suggest. IRMAA's MAGI is AGI plus a single add-back, tax-exempt interest. When line 2a of your return is zero, MAGI and AGI are the same number, and for you the AGI answer is true in practice. When you hold municipal bonds or another source of tax-exempt interest, the two diverge, and IRMAA follows the larger figure. The example above is the reason the distinction exists: an AGI can sit safely under a threshold while the MAGI built on it lands over.

What income counts toward MAGI for IRMAA?

Everything inside AGI, plus tax-exempt interest. An item counts because it sits inside AGI or on line 2a, and an item is out because it never enters AGI or because a deduction removed it from AGI. That single rule produces every row in the table.

Source: SSA POMS HI 01101.010 and the Form 1040 instructions.

Three rows earn a sentence each. Municipal bond interest is free of federal income tax yet still raises Medicare premiums, because pulling it back in is the entire job of line 2a. A Roth conversion is taxable in the conversion year, so the converted amount flows through line 11 that year and can move you up a tier. Realized capital gains travel the same route, including the taxable slice of a home-sale gain above the section 121 exclusion.

Does Social Security count toward MAGI for Medicare?

Partly. The taxable portion of your Social Security benefits is part of AGI, so it counts toward MAGI. The non-taxable portion never enters AGI and never touches the IRMAA calculation at any point. How much of a benefit is taxable depends on your other income and is worked out on the return itself; for IRMAA, the only amount that matters is the amount that reached line 11.

What does not count toward MAGI for IRMAA?

Source: SSA POMS HI 01101.010; QCD and Roth treatment per IRS Publication 590-B.

The confusable pairs are where mistakes happen. A Roth conversion raises MAGI, while a qualified withdrawal from a Roth IRA or Roth 401(k) does not, because qualified Roth distributions are excluded from AGI. A required minimum distribution raises MAGI, while the portion of it sent to charity as a qualified charitable distribution does not, since QCDs up to the annual limit are excluded from AGI. IRS Publication 590-B covers the QCD and Roth rules; the Form 1040 instructions cover the general mechanics.

The test never changes. A dollar that reaches line 11 or line 2a is in your IRMAA MAGI; a dollar that reaches neither is invisible to it.

Which year's tax return does Medicare use?

Generally the return from two years before the premium year. Social Security's manual states it precisely: the MAGI used is the most recent tax information the IRS is able to provide, generally from two years prior to the year for which the premium is being determined, but not more than three years prior (POMS HI 01101.010). POMS gives the pairing itself: 2026 premiums come from the 2024 return.

The "not more than three years" clause is the part almost nobody covers. When your two-year-old return is not yet available, SSA falls back on the three-year-old one, which can put you in the wrong tier. You then hold a correction right, distinct from any life-event appeal: supply the two-year-old return once it exists and SSA issues a new determination (POMS HI 01120.001). The paths for correcting a determination that used the wrong year's return have their own page, as does Form SSA-44 and the life-changing-event process for income that has genuinely dropped since the return SSA read.

Each year's determination reads the newest return on file. A single high-MAGI year therefore raises premiums for one premium year; once a newer, lower return replaces it, the surcharge follows the newer number.

What are the MAGI limits for Medicare premiums?

For 2026 premiums, surcharges begin once 2024 MAGI is above $109,000 single or $218,000 married filing jointly; at or below those figures the standard 2026 Part B premium of $202.90 applies with no adjustment. For 2025 the lines were $106,000 single and $212,000 joint, read from the 2023 return. The full tier tables, including married filing separately, live on the 2026 IRMAA brackets page, and the projected 2027 IRMAA brackets page carries our current estimate of next year's lines.

Is MAGI for IRMAA the same as MAGI for the ACA or an IRA?

No. "MAGI" is not one number. Federal programs define their own versions, and they are not interchangeable: the ACA premium tax credit, the traditional IRA deduction, and Roth IRA contribution eligibility each use their own. IRMAA's is just AGI plus tax-exempt interest, with specifically no add-back for student-loan interest, IRA deductions, or the foreign earned income exclusion.

A figure produced by a generic MAGI calculator, a broker's all-purpose MAGI explainer, or the healthcare.gov glossary is therefore not necessarily your IRMAA MAGI. When the question is Medicare premiums, the two-line definition on this page is the one that applies.

Every definitional statement on this page traces to SSA POMS HI 01101.010 (updated December 2, 2025) and HI 01120.001; QCD and Roth tax treatment traces to IRS Publication 590-B and the Form 1040 instructions.