Most retirees first encounter IRMAA the way they encounter most expensive surprises: in a letter from the Social Security Administration, after the decision that triggered it was already made two years earlier.

IRMAA -- the Income-Related Monthly Adjustment Amount -- is a Medicare premium surcharge applied to higher-income beneficiaries. It is not a penalty in the legal sense. But for a household doing aggressive Roth conversions, processing a large IRA distribution, or selling appreciated property in the wrong year, it functions exactly like one: automatic, retroactive in its calculation basis, and entirely avoidable with planning.

How IRMAA Works

Medicare Part B covers outpatient care, doctor visits, and preventive services. In 2026, the standard monthly premium is approximately $185 per person. Part D covers prescription drugs; premiums vary by plan.

For beneficiaries above certain income thresholds, both premiums increase. The surcharge applies to modified adjusted gross income from two years prior -- so your 2026 Medicare premium is based on your 2024 tax return. This two-year look-back is the feature most households fail to account for when planning large income events.

In 2026, the IRMAA tiers for married filing jointly are approximately as follows. Below $212,000 in MAGI: standard premium, no surcharge. From $212,000 to $266,000: first tier, adding roughly $840 per person per year across Parts B and D combined. From $266,000 to $334,000: second tier, approximately $2,100 per person per year. From $334,000 to $400,000: third tier, approximately $3,360 per person. From $400,000 to $750,000: fourth tier, approximately $4,620 per person. Above $750,000: fifth tier, approximately $5,880 per person annually.

For a couple, these surcharges are per person -- meaning a household in the third tier is paying an additional $6,720 per year in Medicare premiums, on top of standard coverage costs. That is before accounting for any supplemental or Part D coverage.

A Real Situation

David, 61, and Carol, 60, retire in 2028 and begin an eight-year Roth conversion program. In 2028, with zero earned income and approximately $20,000 in brokerage dividends, their MAGI before any conversion is $20,000. They convert $150,000. Total MAGI: $170,000.

In 2026 dollars, that is well below the first IRMAA threshold of $212,000. No surcharge.

But in 2031, they have a decision to make. David's pre-tax IRA has grown despite annual conversions, and their financial planner identifies an opportunity to convert $220,000 that year -- enough to clear significantly more pre-tax balance while rates remain favorable. Total MAGI for 2031: approximately $240,000.

That $240,000 puts them inside the first IRMAA tier on the 2033 Medicare return -- the two-year look-back from 2031 income. Each person pays the Tier 1 surcharge. Additional annual cost: approximately $1,680 for the couple.

The question is not whether $1,680 is prohibitive. It is whether the marginal value of the extra $70,000 conversion at 24% justifies crossing the threshold versus converting $191,000 -- staying just below $212,000 -- and avoiding the surcharge entirely.

The Threshold Management Calculation

The first IRMAA tier is the most important one to manage because it represents the sharpest inflection point. Moving from $211,999 to $212,001 in MAGI triggers a fixed surcharge applied to the entire year. Unlike the income tax system, IRMAA is not marginal. Crossing a tier by $1 costs the same as crossing it by $50,000.

For a household doing annual Roth conversions, the practical rule is: know your IRMAA threshold for the year before finalizing the conversion amount, and stop $5,000 to $10,000 below it rather than pushing to the absolute limit. The buffer matters because brokerage account distributions can vary slightly with year-end dividends, and a surprise $8,000 capital gain distribution from a mutual fund in December can inadvertently push MAGI over the line.

For David and Carol, assuming 2028 IRMAA thresholds are adjusted modestly for inflation to approximately $220,000-$225,000 for the first tier, their conversion target in most years should be calibrated to keep MAGI at $210,000-$215,000. That preserves nearly all available bracket space while protecting against the cliff.

When It May Be Worth Crossing a Tier

Not every IRMAA crossing is worth avoiding. The analysis depends on the conversion amount and the tax differential.

If David and Carol are considering converting an additional $80,000 beyond their IRMAA threshold -- moving from $212,000 to $292,000 in MAGI -- the IRMAA cost is $1,680 for the couple that year. The tax benefit of converting $80,000 at 24% now rather than 32% later is approximately $6,400 in present-value tax savings on that tranche alone, before accounting for compounding inside Roth.

In that case, crossing the IRMAA tier is justified by a comfortable margin. The surcharge is a cost of doing the conversion -- a cost that is smaller than the benefit.

The calculus changes when the conversion amount is small relative to the IRMAA cost, or when income is already deep into a higher IRMAA tier with little marginal conversion benefit remaining. Every household's numbers are different. The point is that IRMAA should be an input to the conversion decision, not a binary stop signal.

The Look-Back Window and Large Income Events

The two-year look-back creates asymmetric risk for households that experience a large, one-time income event -- a business sale, a large inheritance, an unusually large capital gain realization, or a year where a Roth conversion was done without IRMAA modeling.

A couple who sells a rental property in 2026 and realizes $300,000 in capital gains will see their 2028 Medicare premiums increase automatically, even if their 2027 and 2028 incomes are entirely normal. There is no mechanism to smooth that look-back. The surcharge applies to the year it applies.

This is why tax planning for a large income event must include a forward projection of the Medicare impact -- not just the capital gains tax due in the year of the event. For David and Carol, if they were to sell a rental property in 2029, the IRMAA impact on their 2031 premiums is a real planning variable, not an afterthought.

The Appeals Process: Life-Changing Event Exceptions

IRMAA surcharges can be appealed when a qualifying life-changing event has reduced income since the look-back year. Qualifying events include retirement, divorce, death of a spouse, loss of income-producing property, or reduction in work hours.

For David and Carol, retiring in 2028 is a qualifying life-changing event. If their 2028 Medicare premium is being calculated based on their 2026 income of $350,000 -- which would trigger a significant IRMAA surcharge -- they can file Form SSA-44 with the Social Security Administration to request a reduction based on their 2028 retirement income.

The appeal must be accompanied by evidence of the qualifying event and a current or projected income estimate. If approved, the SSA recalculates the surcharge based on the lower income year. This is one of the most underutilized provisions in Medicare planning, particularly for households that retire mid-year or in the year immediately following a high-income event.

What Good IRMAA Planning Looks Like

The households that avoid IRMAA surprises do not avoid income. They model it. By October or November of each year, they know their projected MAGI, the relevant IRMAA threshold, the conversion amount that keeps them below or justifies crossing it, and whether any variable income -- dividends, capital gains, part-time consulting -- could push them over the line before year-end.

For David and Carol, that annual modeling exercise is not a large one. It requires knowing three numbers: current year MAGI to date, the relevant tier threshold, and the amount of conversion capacity remaining. A ten-minute review before finalizing the year-end conversion is the difference between a planned outcome and an avoidable surcharge.

One More Consideration: Part D and Supplement Premiums

IRMAA applies to Part D drug coverage as well as Part B. For a couple on a standard Medicare Supplement plan with Part D coverage, total annual premium exposure -- including standard premiums plus IRMAA surcharges at the second or third tier -- can exceed $15,000 to $20,000 per year. That is a meaningful retirement expense line item that belongs in every income projection, not a footnote.

Planning around IRMAA is not about minimizing Medicare premiums in isolation. It is about making sure that the decisions driving income recognition -- conversions, distributions, capital gain realizations -- are made with full awareness of the downstream Medicare cost. The surcharge is a tax. It just arrives two years late.