Roth Conversions Between 62 and 65: The Three-Year Window Before Medicare Starts Counting Every Dollar
Most people assume they have until 65 to worry about Medicare premiums, but one tax return filed years earlier quietly locks in what you will pay. Knowing which year that is changes how much you can afford to convert.
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A 63-year-old with $1.4 million in a traditional 401(k) has a narrower Roth conversion window than the calendar suggests. Medicare enrollment at 65 uses a two-year lookback on modified adjusted gross income, which means the conversion executed at 63 is the one that sets Medicare premiums at 65. The real deadline arrives earlier than most people expect.
This is the planning window that shows up constantly on Bogleheads and r/financialindependence threads: a semi-retired couple, drawing from taxable brokerage accounts, staring at a large pre-tax balance and wondering how aggressively to convert before Required Minimum Distributions and Medicare surcharges close the door. The math changes depending on whether you convert at 62, 63, 64, or 65.
Why 63 Is the Hinge Year
IRMAA (Income-Related Monthly Adjustment Amount) uses the modified adjusted gross income from two years prior. A conversion completed in 2026 at age 63 lands on the 2028 tax return that Social Security pulls to set 2028 Medicare premiums. Convert at 64, and it hits the year you turn 66. Convert at 65 or later, and every dollar of conversion income is stacking directly on top of Medicare premiums that are already being billed.
The 2026 Part B standard premium is $202.90 per month, with a Part B deductible of $283. IRMAA surcharges kick in above $109,000 for single filers and $218,000 for joint filers. The Part D adjustment starts at $14.50 per month at the first tier and climbs to $91.00 per month above $500,000 single or $750,000 joint. Part B IRMAA scales similarly, and both apply per person on a joint return.
Why the 22% Bracket Is the Real Ceiling
For a married couple in 2026, the 22% bracket runs up to $100,800 of taxable income, and 24% starts at $105,700. The standard deduction is $32,200. That means a couple with no other income can convert roughly $133,000 and still land in the 22% bracket, but they immediately blow through the $218,000 first IRMAA threshold only if they also have pensions, dividends, or a spouse still working.
Here is the tension. Converting $150,000 at 63 in the 22% bracket costs roughly $30,000 in federal tax today. Not converting and waiting for RMDs at 75 on a balance that has doubled means withdrawing at 24% or higher, on top of Social Security, on top of Medicare surcharges. The 22% bracket disappears after the current law sunset window, and the couple who converts at 63, 64, and takes a smaller sip at 65 can move $400,000 or more into a Roth before Medicare enrollment locks in the two-year lookback penalty (we sized up this exact stretch between your last paycheck and your first RMD in a free Roth conversion guide).
Opportunity Cost at a 5% Treasury
The 10-year Treasury yield sits at 5% as of mid-September, up from roughly 4% in late February. That matters because the tax you pay on a conversion is money that could have earned 5% risk-free. Paying $30,000 in tax today to shelter $150,000 forever from ordinary income treatment still wins if that Roth grows for 20 years, but the hurdle rate is higher than it was two years ago. The math tightens.
Social Security amplifies the problem. The 2027 COLA is tracking toward 3.3%, and up to 85% of benefits become taxable once combined income crosses the second threshold. A conversion at 64 that pulls Social Security into the taxable column adds an invisible marginal rate on top of the stated 22% or 24%.
What to Do
- Model the conversion up to the 22% bracket ceiling. Fill the 22% bracket with conversions in each year from 62 through the year you turn 63, because the age-63 return is the last one that will not affect Medicare premiums. Stop at $100,800 of taxable income for a joint filer unless the balance is large enough that 24% is still cheaper than future RMD rates.
- Stagger conversions before Social Security starts. Delaying benefits to 70 gives a clean runway of low-income years. Every year of Social Security you have not yet claimed is a year without the 85% inclusion tax stacking on your conversion.
- Price the IRMAA cliff before signing off. A conversion that pushes a joint return one dollar over $218,000 triggers surcharges for both spouses for a full year. If your combined income lands within $5,000 of a bracket, cut the conversion, because the surcharge on two people can exceed $2,000 for what should have been a $1,100 tax savings.
The window between 62 and 65 is short, and the age-63 tax return does the heavy lifting. Miss it, and Medicare starts counting every dollar.
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Jake has been been working in financial media for almost 15 years. He focuses on all things personal finance for 24/7 Wall St. with high hopes to educate and entertain. Most recently, Jake spent 12 years working various roles at The Motley Fool. He started copy editing fool.com content, worked on premium and marketing campaigns, and helped launch The Ascent, a personal finance brand.
His work has been featured on platforms like MSN, Yahoo Finance, USA Today, and more. He's written about credit cards, social security, ETFs, savings accounts, and just about anything else you can imagine when thinking about money. Jake love to cook, play golf, and tell people he's never had a cavity. (It's true!)
