Inflation-Linked Bonds Can Lift Medicare Premiums Even Before You Sell Them

A retiree who has never sold a bond could still get hit with a higher Medicare charge later, even though the extra income was never received in cash.

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Consider a 66-year-old retiree holding Treasury Inflation-Protected Securities, or TIPS, in a taxable brokerage account. Even without selling any of them, inflation increases their principal, creating $10,000 of added value in 2026. The Internal Revenue Service generally treats that increase as taxable income for that year. The bonds continue paying interest every six months, but the added principal remains invested. That paper income could still push Medicare premiums higher in 2028.

Whether that becomes a problem depends on where a person’s income already stands. The Centers for Medicare & Medicaid Services says income-related surcharges affect about 8% of people with Part B. In 2026, they start above $109,000 for single filers and $218,000 for married couples filing jointly. Those figures show the potential exposure; the 2028 limits have not yet been announced. An inflation adjustment can move someone into a surcharge for the first time or increase an existing surcharge.

Why TIPS Can Create Taxable Income Without a Sale

TIPS principal rises and falls with inflation, as measured by the Consumer Price Index, which rose 3.7% in the year through September 2026. In a taxable brokerage account, that increase usually counts as taxable interest for the year, even though the extra principal stays in the bond. The IRS refers to this as original issue discount, or OID, and it is reported on Form 1099-OID.

The investor receives the adjusted principal when the bond matures, or can sell earlier at market value. In the meantime, the amounts reported as income also increase cost basis, which is the investment amount used to determine taxable gain or loss. That prevents the same increase from being taxed a second time when the bond is sold or matures.

How a $10,000 Increase Can Lead to a Higher Medicare Bill

Social Security calculates the income-related monthly adjustment amount, or IRMAA, using modified adjusted gross income, which is adjusted gross income plus tax-exempt interest. Taxable TIPS inflation adjustments are included in that calculation as interest income. Social Security generally reviews income from two tax years earlier, so 2026 income would normally affect 2028 premiums.

Suppose the retiree files as single and is enrolled in both Part B and Part D. Before the inflation adjustment, Medicare-relevant income totals $105,000, including pension income, taxable Social Security benefits, IRA withdrawals and regular bond interest. Adding the $10,000 TIPS adjustment lifts that figure to $115,000. Using 2026 brackets as an illustration, that moves the filer across the first surcharge level.

At 2026 rates, crossing that threshold adds $1,148.40 a year in surcharges. IRMAA functions like a cliff: being even one dollar over $109,000 triggers the full first-tier charge. A married couple filing jointly faces the same cliff at $218,000, and each spouse on Medicare pays the surcharge.

The inflation adjustment by itself does not qualify for relief through Form SSA-44. A separate qualifying event, such as retirement, fewer work hours or the death of a spouse, may support a request if it lowers the income Social Security uses. A correction may also be possible if the agency relied on incorrect tax information. Simply receiving taxable income without any cash does not count.

Holding the Same Bonds in an IRA Changes the Tax Timing

Inside a traditional IRA or 401(k), the annual TIPS adjustment generally does not create current taxable income for the account owner. Taxable withdrawals can raise Medicare income later, and required minimum distributions eventually reduce control over timing. Keeping the bonds there delays the income; it does not necessarily eliminate the surcharge.

Series I savings bonds provide another timing option. Owners can usually defer reporting interest until redemption or final maturity, whichever comes first, though annual reporting is also allowed. Newly issued I bonds bought from May through October 2026 earn a 4.26% annualized composite rate for the first six months. Older I bonds can carry different rates.

Steps to Take Before Year-End

1. Estimate the taxable adjustment now. Ask your brokerage for a year-to-date estimate instead of waiting for Form 1099-OID early next year. Include it in projected adjusted gross income without double-counting, then add tax-exempt interest. Current thresholds can help show your exposure, but they cannot tell you exactly what future premiums will be.
2. Review other income before year-end. If you do not need the cash now, consider whether an optional IRA withdrawal or investment sale can wait until January. Capital losses can offset capital gains, but they do not offset unlimited amounts of TIPS interest: net losses generally reduce other income by no more than $3,000 a year. Qualified charitable distributions require age 70½, so this 66-year-old would not qualify yet.
3. Estimate next year before buying more TIPS. TIPS held in a taxable account can add income again in any year inflation rises. If the projection shows another move above the threshold, compare buying future TIPS inside an IRA with the tax cost of selling the bonds already owned.