IRMAA Brackets, Explained

A surcharge set by a tax return from two years ago

IRMAA, the income-related monthly adjustment amount, is Medicare's way of charging higher-income retirees more for Parts B and D. The mechanics surprise people twice. First, the income Social Security reads is not this year's: your 2026 premiums are set by the modified adjusted gross income on your 2024 tax return. Second, the tiers are cliffs. Cross a threshold by one dollar and the higher surcharge applies to all twelve months.

The cliff, priced

For 2026 the first single-filer threshold is $109,000 ($218,000 joint). A MAGI of $109,001 puts a single retiree in tier 1 all year: an extra $81.20 a month on Part B and $14.10 on Part D, which is $1,143.60 a year for one dollar of income. The Medicare cost estimator maps all five tiers against your income; the point here is structural: near a threshold, small income decisions (one Roth conversion dollar less, one capital gain deferred) carry outsized premium consequences, and they are decided in the tax year that will be read two years later. A conversion at 63 sets your premiums at 65. A conversion at 66 sets them at 68.

What counts as MAGI for IRMAA

IRMAA's MAGI is your adjusted gross income plus tax-exempt interest. That definition pulls in municipal bond interest that ordinary income tax ignores, and it counts Roth conversions, capital gains, and traditional IRA withdrawals in full. It does not count Roth withdrawals, health savings account spending, or qualified charitable distributions from an IRA, which is exactly why those three are the standard IRMAA levers: QCDs satisfy an RMD without touching MAGI, Roth money spends invisibly, and conversions done before the lookback window (or sized to fill a tier rather than spill over it) cost premiums once instead of annually.

Appeals: the life-events list

If the two-year-old return no longer resembles your life, you can ask Social Security to use a newer year. The qualifying events are specific: marriage, divorce or annulment, the death of a spouse, stopping work or reducing hours, losing income from income-producing property through no fault of yours, losing a pension, or receiving an employer settlement for a company closure or bankruptcy. Retirement itself qualifies as work stoppage, which makes the appeal routine for new retirees whose lookback year was a peak salary year. File Form SSA-44 with documentation (an employer letter, a final pay record) as soon as the premium notice arrives; a successful appeal refunds overpaid premiums. What does not qualify: a voluntary one-year income spike you simply regret, or ordinary market losses.

Planning around the tiers

The households that manage IRMAA well treat the threshold as a budget line. They bunch discretionary income (a property sale, a large conversion) into a single year and accept one year of high premiums instead of three years of moderate ones, because the cliff charges by the year. They finish planned Roth conversions before age 63 where possible. And they keep the charitable giving inside the IRA as QCDs once RMDs begin. None of this requires predicting tax law; it requires knowing that the meter runs two years behind the income, which is the one fact this page exists to deliver.

The 2026 tiers in one place

Five surcharge tiers sit above the standard premium. A single filer crosses into them at $109,000 of MAGI and reaches the top tier at $500,000; joint thresholds are $218,000 and $750,000 (not a clean doubling at the top, a quirk that produces a genuine marriage penalty in the highest band). Part B totals by tier run $284.10, $406.70, $527.30, $649.20, and $689.80 a month, against the $202.90 standard. The estimator places your own income in the table; what matters for planning is that the marginal cost of the dollar that crosses a line is not the tier's monthly extra but twelve times it, because the surcharge locks for the whole premium year.

Married filing separately: the trapdoor tier

Couples who file separately for other tax reasons walk into IRMAA's worst arithmetic. The separate-filer thresholds are compressed: the first tier begins at just $109,000 in the same schedule but the top tier arrives at a far lower income than the joint schedule reaches, and there is effectively no gentle on-ramp. A couple can owe top-tier surcharges on two moderate incomes that would have been standard-premium incomes on a joint return. Living-apart exceptions exist for spouses who lived apart all year, but the default rule is harsh enough that the filing-status decision after 65 should always be priced with premiums included, not taxes alone.

How the notice arrives, and the 60-day clock

Social Security mails an initial IRMAA determination each fall with the following year's premium. The letter cites the tax year used, and that citation is your first check: if it names a return from before a retirement, divorce, or spouse's death that has since cut your income, the SSA-44 appeal described in the main text is the remedy, and it is time-boxed, generally 60 days from the notice, with good-cause extensions. A successful appeal reprices the whole year and refunds premiums already withheld from Social Security checks, which is how most beneficiaries pay Part B. Appeals are decided on documents, so the employer letter or final paystub does the persuading; the form is a cover sheet for evidence, not an essay contest.

The premium is also withheld, not billed, for most people

One mechanical fact softens the cliff's arrival: for the majority of beneficiaries, Part B and its IRMAA surcharge are deducted from the monthly Social Security check rather than billed, so the surcharge appears as a smaller deposit, not an invoice. That invisibility cuts both ways. It is painless to pay, and painless to overlook for years while a fixable lookback year keeps repricing itself into your premiums. The annual notice, not the deposit, is the document to read.

Records to keep: the tax return for every lookback year, the determination letter it produced, and any SSA-44 you filed with its evidence. IRMAA disputes are document-matching exercises, and the household with the folder wins them quickly.