The bill arrives, and the number does not match what the neighbors are paying. That is how most retirees discover IRMAA. About 5.1 million Medicare beneficiaries paid the Part B income-related surcharge in 2025, roughly 7% of the 69 million people on Medicare, and a separate 4.4 million paid the Part D version. Almost all of them learned the acronym the hard way, from a premium notice tied to a tax return filed two years earlier.
What IRMAA Is, and Why It Feels Hidden
IRMAA stands for Income-Related Monthly Adjustment Amount. Social Security adds it to the standard Part B and Part D premiums when income clears a threshold, and it uses tax returns from two years back to decide. For 2026, the first bracket starts at $109,000 for a single filer and $218,000 for a married couple filing jointly, based on 2024 income. Most retirees never see the trigger coming, because the income year that drives the surcharge is already closed by the time the bill arrives. No line on the tax return warns that a Roth conversion or a good stock year will raise a Medicare premium two years later. It shows up in a mailed notice, applied to every monthly premium for the year.
The Dollar Stakes in 2026
The standard 2026 Part B premium is $202.90 per month. Above the first threshold, the total monthly premium jumps in tiers: $284.10 in the first IRMAA tier, $405.80 in the second, $527.50 in the third, $649.20 in the fourth, and $689.90 at the top for individuals at $500,000 or more (or couples at $750,000 or more). At the top tier, the surcharge alone runs nearly $487 more per person per month than the standard premium, roughly $5,844 a year per person, close to $11,688 combined for a couple both at the ceiling. Part D IRMAA stacks on top, adding $14.50 to $91 per month by tier.
Why the Number Keeps Climbing
The share of Medicare enrollees paying IRMAA has moved less than the headline suggests. It rose from roughly 5% in 2007, when the Part B surcharge began, to about 8% by 2019, largely because the income thresholds sat frozen from 2011 through 2019 while incomes kept rising. Since 2020, the thresholds have been indexed to inflation, holding the affected share closer to stable, around 7%.
Two other forces push the raw count up anyway. The Medicare population keeps growing as Baby Boomers age in, so the absolute number of people paying IRMAA rises even at a roughly flat percentage. KFF projects about 5.3 million beneficiaries, or 7.2%, will pay IRMAA by 2030 under current law, modest growth from today. The dollar cost climbs regardless. The Medicare Trustees project the standard Part B premium will rise from $174.70 in 2024 to nearly $300 by 2033, and because IRMAA is set as a multiple of that standard premium, the surcharge scales up alongside it. The 2026 Social Security COLA of 2.8% nudges retiree incomes upward at the same time, tightening the gap to the first threshold.
How Retirees Get Blindsided
The two-year lookback is the trap. A high-income final working year, a Roth conversion, the sale of a long-held rental, or a large one-time distribution in 2024 quietly resets the 2026 Medicare bill, even if current income is far lower. Required Minimum Distributions, mandatory starting at age 73, count fully toward the Modified Adjusted Gross Income used for IRMAA, a frequent trigger for retirees with large traditional 401(k) or IRA balances. The brackets act as cliffs rather than ramps: crossing a threshold by a single dollar triggers the full higher tier for the year, with no phase-in. A $100 miscalculation on a Roth conversion can cost thousands.
What Retirees Can Actually Do
The levers sit on the income side. Time RMDs and Roth conversions to stay under a threshold in a given year. Harvest long-term capital gains at the 0% rate in low-income years. Use Qualified Charitable Distributions, available at age 70½ and capped at $108,000 in 2026, to satisfy RMDs without adding to MAGI.
If a qualifying life event has since dropped income, file Form SSA-44 with the Social Security Administration. Retirement, divorce, the death of a spouse, or the loss of pension income all qualify. A voluntary Roth conversion or a home sale does not, no matter how much either moved MAGI.
Even if the share of retirees paying IRMAA stays roughly flat, the dollar hit for people already inside a bracket keeps growing every year the standard premium rises. This is educational information, not personal tax or investment advice.
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