The IRMAA Surprise Two Years After a Roth Conversion, RSU Vest, or Business Sale

The lookback is mechanical. Each fall, Social Security receives your tax return data from the IRS and uses the most recent year available, normally the return from two years earlier, to set the coming year's premiums. A couple who converts $300,000 in 2026 will see the result in their 2028 Part B and Part D premiums, typically through a notice that arrives late in 2027. If the two-year-old return is not yet available, Social Security may use a three-year-old return and adjust later. Because the premium comes out of Social Security checks for most retirees, the surcharge often looks like a smaller deposit rather than a bill, and many people do not connect it to an event two years earlier.

The age math catches people most often in their early 60s. If you turn 65 in 2028, your first year of Medicare premiums uses your 2026 income, when you were 63. That is frequently the year of a retirement package: the final salary, a bonus, accelerated RSU vesting, a deferred compensation payout, a business sale, or the first large Roth conversion after leaving work. Income at 62 and earlier never affects Medicare premiums, which is why the years before 63 are often the best time for a large one-time income event if you have any control over its timing.

IRMAA MAGI is broader than many people assume. It is adjusted gross income plus tax-exempt interest, so municipal bond interest counts even though it is not federally taxed. It includes wages, RSU income, IRA distributions, Roth conversions, pension income, the taxable portion of Social Security, interest, dividends, and capital gains, including gains from selling a business or rental property. Itemized deductions, including charitable gifts, do not reduce AGI and therefore do not reduce IRMAA MAGI. A $100,000 cash gift to a donor-advised fund in the year of a business sale may lower your income tax but leaves your Medicare premium tier untouched.

RSUs are taxed as W-2 wages at vesting, based on the share price that day, whether or not you sell. A large final vest, or an acceleration of unvested shares at retirement or in a change of control, can add hundreds of thousands of dollars to the year's income. Employers usually withhold federal tax at a flat 22% supplemental rate (37% above $1 million), which often under-withholds for high earners and creates a second surprise at tax time. If you continue to hold the shares after vesting, any later growth is a capital gain, which also counts toward IRMAA in the year you sell.

A business sale concentrates gain into the year of closing unless the deal is structured otherwise. An installment sale, where some of the price is paid over future years, lets you recognize the gain proportionally as payments arrive, which can keep each year's MAGI in a lower IRMAA tier or even below the first threshold. The tradeoffs are real: you carry credit risk on the buyer, interest on the note is ordinary income, depreciation recapture is generally recognized in the year of sale regardless of when you are paid, and installment treatment is not available for publicly traded stock. Earnouts and seller notes need to be modeled for tax and IRMAA together, not after the letter of intent is signed.

SSA-44 relief is narrower than most people hope. The qualifying events are marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property due to a disaster or other event beyond your control, loss or reduction of a pension, and certain employer settlement payments. A Roth conversion is a voluntary choice, so it does not qualify. A capital gain from selling stock, real estate, or a business does not qualify on its own. The nuance: if selling your business or retiring from your job also ended your work, the work stoppage can qualify, and Social Security may then base premiums on a more recent, lower-income year. Whether that fully removes the effect of a sale depends on the facts, so it is worth filing when the work stoppage is real, but it is not a plan.

When income cannot be spread, deliberate bunching can be the better answer. IRMAA is charged per year, so crossing into a high tier once costs one year of higher premiums, while crossing into a lower tier five years in a row can cost more in total. If a large event is unavoidable, it can make sense to pile other discretionary income into the same year, such as a larger Roth conversion or harvesting capital gains, and keep the surrounding years clean. For people past 70 1/2, qualified charitable distributions are the one charitable tool that lowers AGI directly, up to $111,000 per person in 2026, which makes them an ongoing IRMAA lever once RMDs begin.

If you are 61 or 62, treat the next two years of income as your first Medicare premiums. Any retirement package decisions, RSU elections, deferred compensation distribution schedules, or conversion plans should be modeled against the IRMAA tiers that will apply at 65, not just against this year's tax bracket.

Model a known income event the year before it happens. When a business sale, large vest, or conversion is on the calendar, run the MAGI for that year and the two surrounding years, identify which IRMAA tier each lands in, and look for the cheapest arrangement. The choices available before the event, such as installment terms, deferral elections, or conversion size, disappear once it closes.

Spread what can be spread. Installment sales, staged sales of a concentrated position across tax years, and multi-year conversion ladders all keep each year's MAGI lower. If you are still working, maxing out 401(k) deferrals ($24,500 plus catch-up in 2026) and HSA contributions reduces AGI in a heavy RSU year.

Bunch what cannot be spread. If one year is going to land in a high tier regardless, consider moving other discretionary income into that year and keeping the next years under a threshold. Compare the total premiums across all affected years, not one year in isolation.

Use charitable tools that actually move MAGI. Donating appreciated shares instead of selling them keeps the gain off your return entirely. A charitable remainder trust funded before a business sale can spread the income over many years. After 70 1/2, QCDs reduce AGI dollar for dollar, which cash gifts and donor-advised fund contributions do not.

File SSA-44 when you genuinely qualify. If you stopped working, reduced hours, lost a spouse, or lost a pension, file promptly with documentation. It is not available for a conversion or a sale by itself, but a real work stoppage in the same year often is, and many eligible retirees never file.

• Doing a large Roth conversion at 63 or 64 without realizing it sets Medicare premiums at 65 or 66.
• Assuming a charitable deduction in the year of a big sale will lower IRMAA, when itemized deductions do not reduce AGI.
• Accepting accelerated RSU vesting or a lump-sum deferred compensation payout at retirement without modeling the IRMAA effect two years later.
• Closing a business sale for all cash in one year when an installment structure could have kept several years in a lower tier.
• Filing SSA-44 for a Roth conversion or capital gain, which is not a qualifying event, and missing the work stoppage claim that might have qualified.
• Forgetting that municipal bond interest counts toward IRMAA MAGI even though it is not federally taxable.
• Landing a few thousand dollars over an IRMAA threshold for a couple and paying the full surcharge for two people when a smaller conversion would have avoided it.