Most retirement tax planning assumes mistakes are fixable. File an amended return, recharacterize, appeal. Medicare's income-related surcharge is the rare case where the government has written down, in plain language, that it will not listen.
The Two-Year Lookback
The income-related monthly adjustment amount — IRMAA — is a surcharge added to Medicare Part B and Part D premiums for higher-income beneficiaries. It runs on a two-year lag. The 2026 surcharge you are paying now was set by your 2024 tax return. The return you file next spring for 2026 sets your 2028 premium.
For 2026, CMS set the standard Part B premium at $202.90 a month (up from $185.00 in 2025), with a $283 annual deductible. The surcharge tiers begin above $109,000 of modified adjusted gross income for a single filer and $218,000 for a couple filing jointly. Above those lines, Part B is billed at 1.4x, 2.0x, 2.6x, 3.2x, or 3.4x the standard premium — an extra $81.20 to $487.00 a month, with up to $91.00 more per month on Part D.
The Cliff
IRMAA is not a phase-in. It is a step function. One dollar of MAGI over a threshold moves you to the full next tier for the entire year.
Crossing the first line costs $81.20 a month in Part B alone — $974.40 over twelve months, per person. For a married couple both enrolled in Medicare, the same dollar costs roughly $1,949, before Part D. That is the price of a rounding error.
The Part No One Expects
Social Security does allow a "new initial determination" after a life-changing event, filed on Form SSA-44. There are eight: death of a spouse, marriage, divorce or annulment, work reduction, work stoppage, loss of income-producing property, loss of employer pension, and receipt of an employer settlement payment.
SSA's internal manual states that this list "is exclusive." There is no catch-all category, despite what a good deal of secondary commentary suggests. The manual then names what does not qualify — and the list includes capital gains from property sales, lottery and casino winnings, cashing bonds, and, verbatim, "conversion of an IRA."
Read together, the rule is this: IRMAA relief exists for income you lost involuntarily. It does not exist for income you chose to recognize. A Roth conversion, a harvested gain, a large voluntary IRA distribution, a business sale — each can push you over a tier, and none of them gives you a form to file.
What Actually Works
- Model the conversion against the bracket, not just the tax rate. A conversion that looks efficient at a 22% marginal rate can carry a hidden surcharge that lifts the effective cost meaningfully in year two.
- Convert to the line, not past it. Thresholds are indexed and rise annually; a multi-year ladder that stops short of each year's cliff often beats one large conversion.
- Use QCDs if you are 70½ or older. A qualified charitable distribution satisfies RMDs without entering MAGI.
- Check the calendar. 101 days remain in the 2026 tax year. After December 31, the 2028 number is locked.
- Do file SSA-44 if you actually retired. Work stoppage is a qualifying event, and it is the one most newly retired beneficiaries overlook.
The 2027 standard premium is projected at roughly $209.50 in the 2026 Trustees Report; CMS confirms the real figure each November. The tiers will move. The two-year lag will not.
Sources: SSA POMS HI 01120.005 – Life Changing Events; CMS – 2026 Medicare Parts A & B Premiums and Deductibles (November 14, 2025); 2026 Medicare Trustees Report; The Finance Buff – Medicare IRMAA Income Brackets; Kiplinger – Medicare Premiums 2026: IRMAA Brackets and Surcharges