Quick Read – A Roth conversion in 2026 directly sets your 2028 Medicare premiums via IRMAA’s two-year lookback, hitting new enrollees before their first bill arrives. – Crossing an IRMAA threshold by $1 locks in a full-year surcharge, and a $1,000 overage on a joint return costs…
couple roughly $5,200 annually. – Conversions completed in 2025 by someone turning 65 in 2028 escape IRMAA entirely; laddering smaller annual amounts below each bracket preserves the full Roth benefit. – A 63-year-old couple converts $90,000 from a traditional IRA to a Roth in 2026, expecting clean tax-free growth and a smaller required minimum distribution down the road. Their accountant signs off on the tax bill
Two years later, the Social Security Administration sends a letter saying their 2028 Medicare Part B premium will be higher than the standard amount, and their Part D plan will carry an extra surcharge on top. Nobody warned them, because the conversion happened before Medicare enrollment ever entered the picture. This article is for the small slice of pre-enrollees whose taxable income, combined with a planned conversion, could push their modified adjusted gross income above an IRMAA threshold.
CMS says income-related Part B adjustments affect about 8% of people with Medicare Part B. If your joint MAGI in the conversion year will sit well below the current first threshold of $218,000, or $109,000 for single filers, IRMAA may not be an immediate concern. For everyone else approaching 65, the next few sections explain whether a conversion saves money or quietly costs it.