How Medicare's IRMAA Surcharge Works, and Why the Two-Year Look-Back Trips People Up

The Premium Most People Pay, and the Surcharge Some Do

Most Medicare beneficiaries pay the same monthly premium for Part B, which covers doctor visits, outpatient care, and many preventive services. In 2026, that standard premium is $202.90 per month. For the majority of retirees, that is the full story.

But Medicare is not a flat program for everyone. Beneficiaries with higher incomes pay an additional charge on top of the standard premium. This charge is called the Income-Related Monthly Adjustment Amount, or IRMAA. It applies to both Part B and Part D (prescription drug coverage), and it can add hundreds of dollars per month to what a household pays.

Understanding IRMAA matters most for retirees who experience an unusual spike in income, such as selling a business, receiving a large inheritance that generates taxable gains, or converting a traditional IRA to a Roth account in a single year. A one-time event can push you into surcharge territory even if your ordinary income is modest.

The Two-Year Look-Back Explained

The single detail that catches the most people off guard is timing. Medicare does not use your current income to decide whether you owe IRMAA. Instead, it uses your Modified Adjusted Gross Income, or MAGI, from two years earlier.

MAGI is your adjusted gross income plus a few items added back in, most notably tax-exempt interest, such as interest from municipal bonds. For most retirees, MAGI is close to their total taxable income plus any tax-free interest they earned.

Because of the two-year look-back, your 2026 Part B premium is determined by the income you reported on your 2024 tax return. This lag exists because the Social Security Administration relies on the most recent finalized tax data the IRS can share, and 2024 returns are the latest complete records available when 2026 premiums are set.

The practical consequence is that a financial event in one year does not affect your premiums until two years later. Someone who sold a rental property in 2024 might feel perfectly comfortable financially in 2026, only to discover that the earlier sale has raised their Medicare costs for the year.

The 2026 Income Thresholds

For 2026, the IRMAA surcharge begins once your 2024 MAGI crosses a threshold. For single filers, that threshold is $109,000. For married couples filing jointly, it is $218,000. Income at or below those levels means you pay only the standard $202.90 premium with no surcharge.

Above those figures, the surcharges escalate across five income brackets. Each bracket adds a progressively larger amount to both your Part B and your Part D premiums. The higher your income two years ago, the higher the tier you land in, and the tiers can add anywhere from a modest sum to several hundred dollars per month.

The Cliff Effect

One feature of IRMAA surprises people because it does not phase in gradually. IRMAA is a cliff, not a ramp. The moment your MAGI exceeds a bracket threshold by even one dollar, the full surcharge for that tier applies.

Consider two single retirees. One reported a 2024 MAGI of $108,500, just under the first threshold, and pays only the standard premium. The other reported $109,500, just over it, and pays the standard premium plus the first-tier surcharge on both Part B and Part D. The difference in their income was only about $1,000, and it may have been entirely temporary, yet one pays considerably more per month than the other for the entire year.

This cliff structure is why retirees who are near a threshold pay close attention to income-generating decisions, since a small amount of additional income can trigger a full surcharge.

When You Can Appeal: Life-Changing Events

The two-year look-back can feel unfair when your income has since dropped. If you were still working in 2024 and earned a high salary but retired in 2025, your 2026 premium would still reflect that higher working income even though it no longer represents your situation.

The Social Security Administration recognizes this and offers a Life-Changing Event appeal process. If your income has declined because of a qualifying event, you can request that Social Security use more recent income data instead of the two-year-old figures.

Qualifying life-changing events include marriage, divorce or annulment, the death of a spouse, stopping work or reducing hours, loss of income-producing property, and the loss or reduction of certain pension income. To request the review, you file Form SSA-44, titled Medicare Income-Related Monthly Adjustment Amount Life-Changing Event, and provide documentation such as a signed statement, proof of the event, and evidence of your reduced income.

It is worth noting that a large one-time event, such as a Roth conversion or a home sale, is not by itself a qualifying life-changing event. Those raise your income deliberately and do not qualify for the appeal. But an actual drop in ongoing income, such as retiring, generally does.

Why This Belongs in Retirement Planning

IRMAA sits at the intersection of tax planning and health care costs. Because the surcharge depends on income from two years prior, decisions made today ripple forward. Simply knowing that the two-year look-back exists, that the brackets operate as cliffs, and that a Life-Changing Event appeal is available gives retirees the context to understand their Medicare bills and to recognize when a review may be worth pursuing.