How $57,000 in Treasury Interest Could Lift a Retiree’s Medicare Premium Two Years Later

Quick Read

• Treasury interest earned in one year can set Medicare IRMAA premiums two years later, surprising retirees after the income is gone.

• $57,000 in Treasury interest can raise a retiree’s MAGI from $70,000 to $127,000, which can trigger about $1,148 in extra yearly Medicare costs.

• Rolling maturing T-bills into the next year can defer taxable interest without giving up yield, potentially keeping MAGI below the surcharge line.

A widowed father in his 70s who shifted savings into Treasury bills when yields climbed is facing a common retirement issue. With rates around 4% to 4.5%, about $1.28 million to $1.43 million in bills could generate roughly $57,000 in interest over a year. The cash is safe and the income is predictable, but the tax timing is not obvious. That interest can affect his Medicare premium later, including any income-related monthly adjustment amount, long after the bills mature.

Retirement planners say this happens often, and even sensible decisions such as Roth conversions, home sales, and large withdrawals can push income over IRMAA thresholds without warning. A year of strong Treasury interest belongs in that group.

We explained the IRMAA surcharge and the other premium traps that can affect retirees in a free Medicare guide here.

How One Tax Return Can Set a Later Premium

Social Security sets the surcharge using modified adjusted gross income, or MAGI, which is adjusted gross income plus tax-exempt interest income. It relies on tax data from two years earlier to determine the premium for a given year. So if one year’s return is used to set a later premium, the same logic applies here: the father’s tax return one year can determine his Medicare bill two years after that.

Interest from Treasuries is exempt from state income tax but fully taxable federally, so it counts toward adjusted gross income. Municipal bonds do not solve the problem, since their interest is excluded from gross income under federal law, but Social Security adds tax-exempt interest back when it calculates MAGI.

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Where $57,000 of Interest Lands on the Premium Scale

Suppose Social Security, an IRA withdrawal, and a small pension already give Dad about $70,000 of MAGI as a single filer. The Treasury interest would lift that to $127,000. For a single filer, the surcharge begins above $109,000; for joint filers, it begins above $218,000.

Under the 2026 figures, his income would land in the first surcharge tier, which extends to $137,000. Part B would rise to $284.10 a month from $202.90, and Part D would add $14.50 a month. That totals about $1,148 a year, or roughly 2% of the interest.

The later limits have not been published yet. They are adjusted for inflation and have been increasing, from $106,000 in 2025 to $109,000 in 2026. Even so, being $18,000 above the current line is too much for indexing alone to offset.

Moving the Interest Into the Next Year Can Be Better Than Selling

The first, and usually best, option is to change when the interest is taxed while keeping the Treasuries. Consider T-bills. The discount does not count as accruing until the obligation is paid at maturity, sold, or otherwise disposed of. Bills that mature before year-end can be rolled into 13-week, 26-week, or 52-week bills, pushing the interest into the following year. The 52-week bill currently yields about 4.5%, so that move does not sacrifice yield.

Pushing about $18,000 of interest into the next year would bring MAGI back within the limits. That works once, for the year that matters, so long as future years still show only about a year’s worth of interest. It does not work the same way for coupon-paying Treasury notes and bonds, which pay interest on a fixed schedule.

Charitable giving is another option. Qualified charitable distributions from an IRA are excluded from gross income under federal law. If Dad already gives to charity, directing those gifts straight from his IRA reduces his AGI by the same amount.

When Paying the Surcharge Makes Sense

If his MAGI remains well above the limits even after shifting what he can, paying the surcharge may be the practical choice. The first tier takes only a small share of what the Treasuries earn. By contrast, federal income tax on $57,000 of interest in the 24% bracket would cost far more than IRMAA.

Selling the bills to avoid IRMAA is usually the least attractive option for most people in this situation, since moving into municipal bonds does not lower MAGI and holding cash means giving up yield just to avoid the fee.

What To Do Before Year-End

1. Total up projected MAGI now. Add every Treasury maturity scheduled through the end of the year, plus IRA withdrawals and the taxable portion of Social Security, then compare the total with $109,000 or $218,000. If the figure is only slightly over a tier line, rolling bills into the next year is often the least expensive fix.

2. An appeal is unlikely to help. Social Security’s process for reducing IRMAA is generally tied to life-changing events such as stopping work or the death of a spouse. A year of heavy investment income usually does not qualify, so this year’s choices can determine a later premium.

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