A 2.8% Social Security cost-of-living adjustment sounds harmless until it lands on the wrong side of a Medicare income line. For a retired couple with about $216,000 in modified adjusted gross income, the extra benefit can be enough to push them over the first IRMAA threshold. Two years later, that small raise can trigger Medicare surcharges larger than the COLA itself.
If your joint MAGI sits well under $218,000, or under $109,000 if you file as an individual, IRMAA may not be an immediate concern. CMS says income-related Part B adjustments affect roughly 8% of people with Medicare Part B. The risk is concentrated among retirees close enough to the next line that a COLA, capital gain, IRA withdrawal, or interest income can push them over.
The Two-Year Lookback Makes the COLA a Time Bomb
Medicare uses your tax return from two years ago to set this year’s IRMAA. Your 2024 MAGI drives 2026 premiums. Your 2026 MAGI, the one inflated by this January’s 2.8% COLA, will drive 2028 premiums. By the time you see the bill, the income that triggered it is already locked in.
MAGI for IRMAA is line 11 of Form 1040 plus tax-exempt interest from line 2a. Municipal-bond income that feels tax-free still counts. The taxable portion of Social Security benefits, which can be as high as 85%, is already included in AGI. A COLA raises gross benefits and can also increase the taxable amount, especially for households not already at the 85% maximum.
The Math on the First Cliff
Here are the 2026 joint thresholds and the monthly surcharges per person:
| Joint MAGI (2024) | Part B IRMAA / mo | Part D IRMAA / mo |
|---|---|---|
| ≤ $218,000 | $0 | $0 |
| $218,001 – $274,000 | $81.20 | $14.50 |
| $274,001 – $342,000 | $202.90 | $37.50 |
| $342,001 – $410,000 | $324.60 | $60.40 |
The Ohio couple receives roughly $2,000 each in monthly Social Security. The 2.8% COLA hands them about $1,344 a year in extra benefits. Cross the $218,000 line by even one dollar and the combined Part B and Part D surcharges run $2,297 a year for the household. The raise is gone, plus another $953 out of pocket. IRMAA is a cliff, not a phase-in: one dollar over the edge triggers the full tier.
Why the Brackets Don’t Save You
IRMAA thresholds adjust for inflation, but that does not eliminate cliff risk. The 2026 Social Security COLA was based on the CPI-W increase from the third quarter of 2024 to the third quarter of 2025. The first joint IRMAA threshold rose from $212,000 in 2025 to $218,000 in 2026, but any income above that line still triggers the full first-tier surcharge.
The Survivor Trap Doubles the Risk
The single-filer brackets are roughly half the joint brackets. In the year one spouse dies, the survivor may still be able to file a joint return, but later years often shift to single filing unless another filing status applies. Income usually falls, too, but not always by half. A survivor who remains near $109,000 of MAGI can face IRMAA even if the couple had been safely below the joint threshold.
SSA-44 Won’t Bail You Out Here
The IRMAA appeal form applies only when a qualifying life-changing event reduces household income, such as 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 COLA-driven bracket crossing is not a qualifying event. A Roth conversion or home sale generally does not qualify either.
What to Do Before the Lookback Locks In
- Pull a midyear MAGI estimate. Start with projected AGI, including taxable Social Security, pensions, wages, RMDs, interest, dividends, and capital gains, then add tax-exempt interest. If you land within $5,000 of $218,000 joint or $109,000 single, every discretionary dollar between now and December counts.
- Defer or trim controllable income where it makes tax sense. You might push a capital-gains sale into next year, reduce an optional Roth conversion, or use a Qualified Charitable Distribution from an IRA if you are 70½ or older to satisfy charitable intent without increasing AGI.
- Re-run the math each fall. CMS typically publishes the next year’s Medicare premiums and income-related adjustments late in the year, and Social Security applies the two-year lookback using the tax return data available to it. The line moves; check whether your income moved with it.
The COLA arrives quietly. So can the Medicare bill it helps trigger. Watch your proximity to the next IRMAA line, because a raise meant to protect your buying power can disappear if it pushes your MAGI over a cliff.
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