A Couple Built a Treasury Ladder for Safe Income. The Yields Nudged Them Toward Medicare’s $218,000 IRMAA Cliff.

A married couple, both about 69 and on Medicare, built a Treasury ladder of bills and notes to generate steady, government-backed income while rates sit near multi-year highs. Two-year Treasuries are near 4.2%, 10-year notes around 4.5%, and 30-year bonds close to 4.9% in mid-June 2026. On a seven-figure ladder, that interest adds up fast.

Here is the wrinkle. Every dollar of Treasury interest is fully taxable at the federal level, even though states leave it alone. That income lands on the tax return as ordinary interest and flows straight into the modified adjusted gross income figure (MAGI) that Medicare uses to set premiums. A retirement plan built around safety can still trigger the income-related Medicare charge.

A common question on retirement forums sounds something like, “We built our ladder for income, and now our accountant says we are a few thousand dollars from a Medicare surcharge. What did we miss?” The answer is almost always the same: the interest counts.

The $218,000 line and the two-year delay

For 2026, joint filers stay on the standard Part B premium of $202.90 a month as long as their MAGI is $218,000 or less. One dollar above that threshold and the Income-Related Monthly Adjustment Amount, known as IRMAA, kicks in for both spouses. The surcharge applies in full at the first dollar over a tier. At the top tier, joint filers pay $689.90 per person per month for Part B, with a separate Part D surcharge on top.

The part most retirees miss is the timing. IRMAA looks at income from two years earlier. As Suze Orman put it on her Women & Money podcast, “IRMAA is based on your modified adjusted gross income from two years prior. So they’re always looking back two years.” That means 2026 Medicare premiums are set by the 2024 tax return. The Treasury interest this couple is earning in 2026 will not change their premiums until 2028.

A ladder that throws off $40,000 in interest this year could be the difference between a clean 2028 and a year where both spouses pay hundreds of dollars more per month for the same Medicare coverage.

How this connects to the rest of the picture

Treasury interest does not sit alone on the return. It stacks on top of Social Security, any pension, required minimum distributions (RMDs) once they begin, and any capital gains from rebalancing. The 2.8% Social Security cost-of-living adjustment (COLA) for 2026 nudges benefits higher too, and a portion of that counts toward MAGI.

The bigger risk is bunching. If a ladder is built so that several large maturities pay interest in the same calendar year, or a CD matures alongside a fund distribution, the household can sail past $218,000 in a year where it would otherwise stay under. CDs, for context, look weaker on yield: the national average 12-month CD rate is just 1.65%, which is why so many retirees moved to Treasuries in the first place.

One reassuring detail: an IRMAA spike from a one-time income event lasts only a year. Income comes back down the following year, and premiums follow two years after that.

What actually matters before December

1. Map MAGI before year-end. Add up expected Treasury interest, the taxable portion of Social Security, any tax-exempt interest, pension, distributions, and realized gains. If the total looks close to $218,000, there is still time to tweak.
2. Use tax-advantaged space where you can. Treasuries held inside an IRA do not generate currently taxable interest. For new ladder rungs, taxable accounts and IRAs are far from interchangeable on an IRMAA basis.
3. Stagger maturities thoughtfully. Spreading interest payments across calendar years, rather than letting them bunch, can keep a household on the safe side of the cliff.

If a true life-changing event is involved, such as a spouse stopping work or losing a pension, Social Security will reconsider the IRMAA determination with Form SSA-44. That is a useful escape hatch, though it does not cover earning more interest than expected.

The hardest mistake to undo is forgetting that safe income is still income, and that Medicare’s clock runs two years behind. A conversation with a tax preparer in October or November, while there is room to act, tends to be worth far more than the same conversation in April. Every household’s mix of accounts and income sources is different, so the exact dollar threshold to worry about varies.