You Didn’t Sell a Thing — but a $30,000 Fund Payout Just Raised Your 2028 Medicare Bill

Picture a retired couple in late December 2026, both 68, MAGI tracking around $205,000 for the year. They feel comfortably under the first IRMAA threshold. Then a brokerage statement lands: their large-cap mutual fund declared a $30,000 year-end capital-gains distribution. They did not sell a share. They did not rebalance. They did nothing. And their 2028 Medicare premiums just went up.

If your household income runs well below the first IRMAA tier, this article does not apply to you. Roughly 8% of Medicare Part B beneficiaries pay any IRMAA surcharge at all. The readers this hits are the ones hovering within $20,000 or $30,000 of a bracket, because that is the zone where a single fund distribution can move the needle.

What Actually Counts as MAGI

For IRMAA, modified adjusted gross income is your Form 1040 line 11 AGI plus line 2a tax-exempt interest. That second line matters. Municipal bond interest feels tax-free at filing time, but Medicare adds it back when sizing your surcharge. So does every fund distribution that hit a 1099-DIV: ordinary dividends, qualified dividends, and the capital-gains distributions a fund pays out when its manager sells appreciated holdings inside the portfolio. No action by you is required for that income to count. The fund sold. You owe.

That is the trap. A taxable account holding actively managed equity funds throws off distributions whether you want them or not, and a strong market year compounds the problem because managers realize larger gains. December statements are when retirees discover the number.

The 2026 Income Drives the 2028 Bill

SSA uses a two-year lookback. Your 2026 tax return, filed in spring 2027, sets your 2028 Part B and Part D premiums. There is no in-year adjustment and no retroactive smoothing. The income on that return is the income Medicare uses, full stop.

Here is what the first tier costs under 2026 CMS rules, which is the rate card the article’s couple will see applied to their 2028 premiums if the brackets hold roughly flat:

The couple at $205,000 plus a $30,000 distribution lands at $235,000. Each spouse would fall into the first IRMAA tier using the 2026 thresholds shown above, triggering additional Part B and Part D premiums. Across both spouses, the surcharges can add a meaningful four-figure cost over the course of a year, all because of income the couple may not have actively realized themselves.

One more thing about brackets. The 2026 Social Security COLA was 2.8%, and inflation has continued to push many retirees’ incomes higher. IRMAA thresholds are indexed for inflation, but the adjustments may not fully offset growth in taxable income from Social Security, required minimum distributions, dividends, and investment gains. As a result, some households can drift into higher IRMAA tiers even when their income is only keeping pace with broader economic trends.

SSA-44 Will Not Save You

Readers surprised by an IRMAA surcharge often look to SSA-44, the form used to request a premium adjustment after certain life-changing events. It generally will not help in this situation. The qualifying events are limited to things like marriage, divorce, the death of a spouse, a work stoppage or reduction, the loss of income-producing property, the loss of pension income, or an employer settlement. A mutual fund distribution is treated as investment income, not a qualifying life-changing event, so an appeal based solely on that distribution is unlikely to succeed. Once the income is reported on the tax return used for the IRMAA determination, Medicare will generally use it when calculating future premiums.

What to Do Before December 31

• Pull each fund’s estimated year-end distribution now. Most large fund families post preliminary capital-gains estimates in October and November. If you are within $30,000 of the next bracket, that PDF is the most valuable document in your inbox.
• Harvest losses in the taxable account to offset projected distributions. Realized losses reduce AGI dollar for dollar against capital gains. A $30,000 distribution paired with $30,000 of harvested losses lands at zero net gain.
• Move high-distribution funds out of the taxable account over time. Hold actively managed equity funds inside IRAs or 401(k)s, and keep broad-market ETFs (which distribute very little) in the taxable account. This will not fix 2026, but it stops the same problem from setting your 2029 and 2030 Medicare bills.

Sources: CMS 2026 Medicare Parts A & B Premiums and Deductibles fact sheet; SSA guidance on SSA-44 and IRMAA. Article uses 2026 plan-year rules applied to the 2028 IRMAA lookback.