A Popular Retirement Tax Strategy Could Quietly Raise Your Medicare Premiums by Thousands
Roth IRA conversions done without attention to Medicare income thresholds can trigger surcharges of $2,000 to $8,000 or more annually on Part B and Part D premiums — but careful sizing and timing can prevent it.
The Collision Between Roth Conversions and Medicare
If you are between 62 and 70, navigating Medicare decisions alongside retirement income planning, there is a financial trap hiding in plain sight. It has nothing to do with choosing the wrong plan during open enrollment. It is a collision between Roth IRA conversions and the income-based surcharges that determine what you actually pay for Medicare Part B and Part D.
A Roth IRA conversion moves money from a pre-tax retirement account, such as a traditional IRA or 401(k), into a Roth IRA. You pay income taxes on the converted amount now, and from that point forward, all growth and qualified withdrawals are completely tax-free. There is no income limit on conversions.
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Done well, the strategy can save tens of thousands of dollars in lifetime taxes. Done carelessly, it can quietly inflate Medicare premiums by thousands of dollars a year.
The Gap Years Window
Financial planners refer to the “gap years” as the stretch between leaving full-time work and when mandatory retirement income kicks in. Someone who retires at 62 but delays Social Security until 67 or later, with required minimum distributions not starting until age 73, may have a decade or more of unusually low taxable income.
That drop in income creates a conversion opportunity. Your effective tax rate can fall to the lowest it has been in your entire adult life. But the income you report during these gap years directly shapes what Medicare charges you in premiums — not today, but two years from now.
That delayed impact is where costly surprises live.
How IRMAA Works Against You
IRMAA stands for Income-Related Monthly Adjustment Amount. It is an additional charge added on top of standard Medicare Part B and Part D premiums for beneficiaries whose income exceeds certain thresholds. It is not a separate bill — it is baked into what you pay each month.
The critical detail that catches many retirees off guard is the two-year lookback. A 2026 Roth conversion affects your 2028 premiums by an estimated $2,000 to $8,000 or more annually for large conversions.
A single tax decision made this year could raise Medicare Part B and Part D premiums two years from now by several thousand dollars. For someone comparing Advantage plans, weighing Medigap policies, or optimizing Part D drug coverage, this is not a footnote. It is a central planning variable.
A large Roth conversion raises your modified adjusted gross income, which is the figure Medicare uses to determine whether you owe IRMAA surcharges. Converting aggressively without watching the IRMAA thresholds may wipe out part of the tax benefit with inflated health care costs.
The Bracket-Fill Strategy
The problem is avoidable if you size conversions deliberately. You do not need to convert your entire traditional IRA balance at once. Doing so could push you into a much higher tax bracket and largely defeat the purpose.
The smarter move is to convert only enough to fill your current bracket without spilling into the next one. If you are in the 22% bracket with $80,000 of headroom before reaching 32%, converting up to that amount each year means paying 22% on the converted funds rather than potentially 32% or more later, once required minimum distributions are forcing taxable income whether you need it or not.
Spread across several gap years, this approach lets you systematically shift a large pre-tax balance into tax-free territory at the lowest possible cost. Keeping your conversion within a range that avoids IRMAA thresholds protects your Medicare costs alongside your tax bill.
Every dollar converted also reduces your future required minimum distribution burden, which compounds the benefit over time. Smaller future RMDs mean lower income in later years, which means lower IRMAA exposure for the rest of your time on Medicare.
Conversion income can also increase the taxable portion of Social Security benefits in the year it occurs — one more reason to convert during the gap years, before those benefits begin.
Why 2026 Offers Unusual Clarity
The tax landscape has gotten meaningfully clearer. TCJA rates, which many feared would increase after a potential 2026 sunset, are now permanent under the One Big Beautiful Bill Act (OBBBA, 2025). That removes years of planning uncertainty.
For Medicare decision-makers, permanent tax rates mean you can plan multi-year conversion strategies with greater precision, projecting modified adjusted gross income across several years and mapping exactly where IRMAA thresholds fall relative to conversion amounts. The uncertainty that previously made this planning difficult has been substantially reduced.
Pay Taxes From Outside the IRA
This execution step matters more than people expect. Pay conversion taxes from a separate taxable account, not from the IRA funds themselves. T. Rowe Price explains that using IRA money to cover the tax bill reduces the amount that actually lands in your Roth, and if you are under 59½, that withdrawn amount may also trigger a 10% penalty.
If you do not have outside funds available to cover the taxes, that is a meaningful signal that the timing may not be right.
For someone managing Medicare costs carefully, every dollar that fails to make it into the Roth is a dollar that does not compound tax-free — reducing the long-term payoff that is supposed to justify the short-term IRMAA hit.
Deadlines and Rules
Contact your IRA custodian to initiate a direct transfer. The conversion must be completed by December 31 of the tax year you want it to count toward. Most advisors recommend submitting paperwork by November 30 to allow for processing.
On the five-year rules: there are two distinct ones, and they operate independently. To withdraw earnings tax-free, your Roth IRA must have been open for at least five tax years and you must be 59½ or older. That clock starts January 1 of the year you made your very first Roth contribution.
Each individual conversion also carries its own five-year clock for penalty-free access to converted principal. Fidelity walks through both rules in detail here. For most people converting in their early 60s, the second rule is less of a practical concern, but it is worth understanding.
One final point on permanence: since 2018, Roth conversions cannot be reversed. Once you convert, it is done. There is no undo button if markets drop or circumstances change.
When a Roth Conversion Does Not Make Sense
The strategy works best when your current tax rate is lower than what you expect in retirement. If you genuinely anticipate being in a lower bracket later, converting now at a higher rate does not pencil out.
Kiplinger outlines scenarios where caution is warranted: no outside funds to cover the tax bill, a short runway for tax-free compounding to work, or a conversion amount that would spike Medicare costs past what the long-term benefit justifies.
That last scenario is worth underscoring for anyone in the Medicare enrollment window. If a conversion triggers IRMAA surcharges that persist across multiple years, and the Roth balance is not large enough or held long enough for tax-free growth to outweigh those extra premiums, the math may not work in your favor.
What This Means for Your Medicare Planning
If you are weighing plan options, comparing Part D formularies, or calculating what you can afford in monthly premiums, your retirement tax strategy is not a separate conversation. It is the same conversation.
A Roth conversion done in 2026 will show up in your 2028 Medicare premium calculations. You need to model that two-year lookback before converting a single dollar.
The gap years are finite. Once Social Security checks and required minimum distributions start stacking up, the window of low taxable income closes — and it does not reopen. For those with significant pre-tax balances and a multi-year window of lower income ahead, these years represent a rare opportunity to reposition retirement savings at a meaningful tax discount.
But the size and timing of each conversion must account for the premium bracket, too. Staying under IRMAA thresholds while filling your tax bracket is the difference between a strategy that saves money across the board and one that trades lower taxes for higher health care costs.
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Production of this article included the use of AI. It was reviewed and edited by a team of content specialists.
This story was originally published March 19, 2026 at 8:54 AM.
