What is IRMAA?

IRMAA works on a two-year lookback: this year's Medicare premiums are generally based on the MAGI reported on your tax return from two years prior, so for 2026 the determination is generally based on 2024 MAGI. That delay means income events well before Medicare enrollment, such as a Roth conversion, a business sale, or a large capital gain, can quietly raise premiums years later.

For 2026, the first surcharge tier begins once MAGI exceeds $109,000 for single filers or $218,000 for married couples filing jointly, and it rises through additional tiers as MAGI climbs further, according to the Centers for Medicare & Medicaid Services' 2026 Medicare Part B premium and deductible fact sheet. Depending on the tier, the 2026 Part B surcharge ranges from about $81.20 to $487.00 per month and the Part D surcharge ranges from about $14.50 to $91.00 per month, on top of the standard premiums. Crossing a threshold by even a small amount can move an entire household's premium to the higher tier for that bracket.

Required minimum distributions (RMDs) can push retirees into IRMAA territory precisely when they may least expect it, since RMDs are mandatory and are added directly to MAGI. Similarly, a large one-time Roth conversion could trigger a temporary IRMAA surcharge two years later, because that year's IRMAA is based on MAGI from two years earlier.

Because of the lookback, some retirees use strategic Roth conversions in lower-income years, for example between retirement and the start of RMDs or Social Security, or spread conversions over several years, to help manage future taxable income and potentially reduce IRMAA exposure later. The right approach depends on the full financial picture, and it is not guaranteed to reduce costs in every case.

Beneficiaries who experience a life-changing event, such as retirement, the loss of a pension, marriage, or divorce, may be able to request a reconsideration of their IRMAA determination directly with the Social Security Administration using Form SSA-44. Coordinating the timing of RMDs, Roth conversions, and other income events may help retirees avoid or minimize IRMAA surcharges, though outcomes depend on individual circumstances.