The $109,000 Income Threshold That Triggers a $1,148 Medicare Surcharge Most Retirees Miss

Roughly 8% of Medicare beneficiaries pay an Income-Related Monthly Adjustment Amount, so most readers whose household income sits well under the first tier can stop here. Everyone else should keep reading. The first tier catches a single filer whose 2024 modified adjusted gross income tops $109,000, or a joint filer above $218,000, and it adds a 2026 surcharge to both Part B and Part D premiums.

The Scenario

A 67-year-old retiree files a single return for tax year 2024. Her adjusted gross income reads $108,400. She also collected $900 in tax-exempt municipal bond interest, which she assumed stayed invisible because it escapes federal income tax. The Social Security Administration adds that line 2a interest to her line 11 AGI, arrives at $109,300 of MAGI, and drops her into the first IRMAA bracket for 2026. Her January 2026 premium notice lands higher than she expected, and the surcharge rides every monthly bill for the rest of the year.

The Cliff, the Lookback, and the Math

IRMAA runs on a two-year income lookback, so 2024 MAGI sets 2026 premiums. A 2024 return already filed locks the 2026 surcharge in place. Looking ahead, 2025 income will drive 2027 premiums, and 2026 income will drive 2028. Income already reported cannot be unwound, so only future-year MAGI remains within a retiree’s control.

The first tier operates as a cliff: one dollar over the threshold triggers the entire surcharge. For 2026, that surcharge arrives in two pieces.

• Part B adds $81.20 per month on top of the $202.90 standard premium, for a total of $284.10 per month.
• Part D adds $14.50 per month on top of whatever the plan charges.

Together those two pieces come to $95.70 per month, or about $1,148 per year, per person. A married couple where both spouses are enrolled each pays the surcharge separately when their joint return tops $218,000, doubling the household hit to roughly $2,296.

The hold-harmless provision, which shields most beneficiaries from a net drop in their Social Security check when premiums rise, does not cover IRMAA payers. A first-time move into a surcharge bracket can therefore cut a retiree’s net Social Security income outright. The Part D piece is where many readers lose track, because that surcharge bolts onto a private plan premium they already pay separately rather than appearing as a single line on a Medicare notice.

What Counts as MAGI

For IRMAA purposes, MAGI means adjusted gross income (Form 1040, line 11) plus tax-exempt interest (line 2a). That definition is both narrower and broader than it sounds. A handful of income types routinely push retirees across the threshold:

• Roth conversions. The converted amount is fully taxable in the year it is made, so it lands in AGI in full.
• Required Minimum Distributions. RMDs from traditional IRAs and 401(k)s begin at age 73 and count in full toward MAGI.
• Capital gains. A home sale above the $250,000 single or $500,000 joint exclusion, or a portfolio rebalance, flows directly into AGI.
• Tax-exempt municipal bond interest. It escapes federal income tax but still counts toward IRMAA MAGI.
• Interest and dividends. Treasury interest, bank interest, and ordinary dividends all count in full.

Social Security benefits enter MAGI through their taxable portion on line 6b, which can reach up to 85% of benefits for higher-income retirees. Annual cost-of-living adjustments lift those benefits each year, which gradually raises the MAGI of retirees who depend on Social Security for a meaningful share of their income, nudging some toward the first IRMAA bracket with no deliberate income move on their part.

The Survivor Trap

The 2026 brackets are roughly twice as wide for joint filers as for singles. When one spouse dies, the survivor shifts to single-filer status starting the year after the death. Household income typically falls by far less than half: pensions and Social Security often continue at a reduced rate while core spending needs hold steady. The same dollar of income that sat comfortably inside the joint zero-surcharge band can clear the single threshold the following year. The bracket moved; the income did not.

What SSA-44 Will and Will Not Do

Form SSA-44 allows a beneficiary to ask the Social Security Administration to base the surcharge on more recent income rather than the two-year-old return. The form applies only to specific qualifying life-changing events: marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property, loss of pension income, or an employer settlement payment.

A Roth conversion does not qualify. A home sale does not qualify. An RMD does not qualify. A large capital gain from a portfolio rebalance does not qualify. The rules treat those events as voluntary or anticipated, so the surcharge they create stays in place for the full year. SSA-44 is designed strictly for situations where income has fallen involuntarily.

Planning Levers

• Project MAGI for the current tax year before December 31 by combining expected AGI, tax-exempt interest, and any planned Roth conversion or RMD. When the projected total lands within a few thousand dollars of $109,000 (single) or $218,000 (joint), postponing discretionary income or accelerating deductions can keep MAGI below the threshold.
• File SSA-44 promptly after a qualifying life event. There is no fixed deadline, but submitting quickly with supporting documentation (a retirement letter, death certificate, divorce decree, or pension termination notice) gets the premium adjusted sooner. Include an estimate of the new year’s income.
• Factor the surcharge into Roth conversion math when household income sits within roughly $20,000 of a bracket boundary. A conversion that looks efficient at a 22% or 24% marginal rate can cost more in total once a full year of IRMAA on both Part B and Part D is added, along with the extra taxable Social Security the higher income creates.

A Legislative Note for 2026 and Beyond

The One Big Beautiful Bill Act, signed into law on July 4, 2025, did not change the IRMAA brackets or surcharge amounts for 2026. However, it delayed two finalized CMS rules that would have made it easier for lower-income Medicare beneficiaries to access Medicare Savings Programs, which help with premiums and cost-sharing. Those rules are now blocked until at least October 2034. For higher-income retirees facing IRMAA, the surcharge structure itself remains unchanged, but the broader Medicare cost landscape continues to shift as the legislation works through implementation.

Editor’s note: This update refreshes the IRMAA prevalence figure from “fewer than one in ten” to the more precise CMS-cited figure of roughly 8% of Part B beneficiaries, adds context on the household cost doubling for couples where both spouses are enrolled, and notes the One Big Beautiful Bill Act’s delay of CMS rules affecting Medicare Savings Programs through at least 2034.

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