She Will Convert to a Roth at 63 and 64 and Stop a Year Before Medicare. Medicare’s First Two Premiums Will Be Priced on 63 and 64.
Stopping Roth conversions before Medicare begins feels like a clean escape from IRMAA surcharges, but Medicare does not read the calendar the way most retirees expect, and those earlier conversions may already be waiting on file.
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A 63-year-old retiree converts part of her traditional IRA to a Roth in 2026, does it again in 2027, then relaxes. She assumes the tax cost ends when Medicare begins at 65. She’s wrong. Medicare reaches back two years and finds both conversions anyway.
Whether Medicare charges more depends on how much the conversion adds to the rest of her income. IRMAA affects roughly 8% of people with Medicare Part B. Single filers with income at or below $109,000 and joint filers at or below $218,000 pay the standard $202.90 monthly Part B premium. If your income, conversions included, falls well under that line, you face no surcharge. The math below matters for anyone converting enough to cross it.
Her Conversion at 63 Sets Her First Medicare Premium
She turns 63 in 2026, 64 in 2027 and reaches Medicare at 65 in 2028. IRMAA is set from the tax return two years back: her 2026 return sets 2028 IRMAA; her 2027 return sets 2029 IRMAA.
If she enrolls partway through 2028, the surcharge applies only during the months she has Medicare. The 2027 conversion then lands on 2029, her first full calendar year of coverage, and could create a second surcharge year.
Why Money She Never Spent Still Counts
A Roth conversion moves pretax money into a Roth, and the taxable amount generally counts as ordinary income that year. It flows into adjusted gross income (AGI). Social Security defines modified adjusted gross income (MAGI) as your total adjusted gross income and tax-exempt interest income, so municipal bond interest that escapes federal income tax still counts. The converted dollars never touch her checking account, yet Medicare treats them as income.
Two Conversion Years Can Mean Two IRMAA Years
Picture a single filer with $66,000 of AGI from a pension and Social Security (assume her benefits already sit at the maximum taxable share) plus $4,000 of muni interest. Her MAGI is $70,000, leaving $39,000 of room before the surcharge kicks in. Assume her traditional IRA holds only pre-tax money, so the full conversion is taxable.
A $50,000 conversion raises her MAGI to $120,000, inside the tier that runs from $109,000 to $137,000. That tier adds $81.20 a month to Part B, for a total of $284.10, plus $14.50 a month on Part D. At 2026 rates, a full year in that tier costs $1,148.40. Her 2026 conversion could affect only part of 2028 if she starts Medicare midyear, while the 2027 conversion could affect all of 2029.
The cliff is immediate. At $109,000 she pays the standard $202.90. At $109,001 she jumps to $284.10, plus the Part D surcharge if she has drug coverage. Crossing the line by a single dollar triggers the full tier.
Future thresholds are indexed, so use current thresholds only as a yardstick. Stopping conversions at 65 leaves both tax returns on file for Medicare to read (we laid out IRMAA alongside the other premium traps retirees walk into in a free Medicare guide here).
Make the Conversion Worth the Medicare Cost
The conversion creates a tax bill now, but that is only one side of the trade. A larger Roth balance can mean smaller required minimum distributions (RMDs) later and more money available for qualified tax-free withdrawals. For someone who is 63 in 2026, RMDs generally begin at 75. IRMAA is another cost to put into the equation before deciding how much to convert.
Size beats speed here. A $35,000 conversion puts her MAGI at $105,000, below the threshold, with zero surcharge. She moves less money per year, so she needs more conversion years to reach the same balance.
A Roth conversion itself is not an SSA-44 event. She cannot ask Social Security to lower IRMAA simply because the conversion was voluntary, temporary or will not happen again.
Map Both Calendars Before December 31
The useful decisions happen before the conversion, not when the Medicare notice arrives two years later.
- Use today’s brackets as a guide, not a target. The 2028 thresholds are not set yet, so don’t build a conversion to land exactly at $109,000 single or $218,000 joint. Leave room for dividends, interest and other year-end income.
- Leave a buffer in 2027. You won’t know the 2029 thresholds when you convert, and a surprise dividend can push you over a tier.
- Model both conversion years together. A conversion that fits comfortably in 2026 can still leave too little room for another one in 2027, so decide how much you want to move across both tax years before either year closes.
A Roth conversion can still be a smart trade. The mistake is pricing only the tax bill and forgetting the Medicare bill that can follow two years later.
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Gerelyn Terzo is the author of dividend investing handbook "Dividend Investing Strategies: How to Have Your Cake & Eat It Too." A veteran financial journalist, she covers agri-finance for outlets like Global AgInvesting and the broader stock market and personal finance for 24/7 Wall Street. She began at CNBC and later helped launch Fox Business in New York. Gerelyn currently resides in Woodland Park, Colorado and dabbles in nature photography as a hobby.
