Medicare IRMAA after a Roth conversion in 2026: why one tax move can raise future premiums

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Medicare IRMAA in 2026 is based on modified adjusted gross income, and a taxable Roth conversion can push that income above a Medicare premium threshold. That sentence is not dramatic. It is also the reason a clean retirement tax move can come back later wearing a Medicare badge. The Roth conversion itself may still be smart. The trap is thinking the tax bill is the only bill. A conversion can reduce future required minimum distributions. A conversion can move money into an account with qualified tax-free withdrawals. A conversion can help heirs avoid inheriting a fully taxable IRA. But if the conversion raises adjusted gross income, it may also raise Medicare Part B and Part D premiums for a later year. That later-year timing is where people get ambushed. Medicare does not usually look at the income year you are living in right now. For 2026 IRMAA, Social Security says it generally uses the federal tax return filed in 2025 for tax year 2024. Sometimes it may use a 2023 return if that is the newest IRS data available. So the premium pain can feel delayed. You do the conversion. You file the tax return. Then a Medicare notice appears later and says your monthly premium is higher. Very elegant system. Very expensive little jump scare. This article is a premium impact checklist, not personalized tax advice. Use it to spot the Medicare side effects before you convert. Use it to ask better questions to a CPA, enrolled agent, financial planner, or SHIP counselor. And please do not treat Roth conversion calculators like magic vending machines. They are useful. They are not your mom.

The core rule to remember

IRMAA stands for Income-Related Monthly Adjustment Amount. It is an extra Medicare premium amount for higher-income beneficiaries. SSA explains that higher-income beneficiaries may pay more for Medicare Part B and Medicare prescription drug coverage. Part B covers doctors’ services, outpatient care, and other medical services. Part D covers prescription drug coverage. If IRMAA applies, it can hit both. That matters because a Roth conversion is usually taxable. IRS Publication 590-A says that a traditional IRA amount converted into a Roth IRA may be included in gross income and subject to ordinary income tax. The same IRS publication says you generally include in gross income the traditional IRA distributions you would have included if you had not converted them. That taxable income can raise adjusted gross income. SSA defines MAGI for Medicare premium purposes as total adjusted gross income plus tax-exempt interest income. So the basic chain is simple. Traditional IRA conversion becomes taxable income. Taxable income can raise AGI. AGI can raise Medicare MAGI. Medicare MAGI can cross an IRMAA bracket. Crossing a bracket can raise Part B and Part D premiums. This is why the question is not only, “Can I afford the income tax?” The better question is, “Can I afford the income tax plus the future Medicare premium effect?” That one extra clause is where the adult supervision lives.

The 2026 IRMAA table you need before converting

SSA lists the standard 2026 Part B premium as $202.90 per month. Medicare.gov also lists the 2026 Part B premium as $202.90 per month, or higher depending on income. For 2026, SSA’s first IRMAA threshold is MAGI above $109,000 for most individual filing statuses. For married filing jointly, SSA’s first 2026 threshold is MAGI above $218,000. If income stays at or below those amounts, the 2026 standard Part B premium applies. If income crosses above those amounts, the first 2026 IRMAA tier adds $81.20 per month to Part B. The first 2026 Part D IRMAA tier adds $14.50 per month to the drug plan premium. That first tier is not the whole table. For most single filers, the 2026 tiers move from above $109,000 to $137,000, then above $137,000 to $171,000, then above $171,000 to $205,000, then above $205,000 and less than $500,000, then $500,000 or more. For married filing jointly, the matching 2026 tiers are above $218,000 to $274,000, above $274,000 to $342,000, above $342,000 to $410,000, above $410,000 and less than $750,000, then $750,000 or more. The highest listed 2026 tier for most single and joint filers adds $487.00 per month to Part B. The highest listed 2026 tier adds $91.00 per month to Part D. Married filing separately has its own compressed table. For married filing separately, SSA lists the standard premium up to $109,000 of MAGI. Above $109,000 and less than $391,000, SSA lists a Part B add-on of $446.30 and a Part D add-on of $83.30. At $391,000 or more, SSA lists a Part B add-on of $487.90 and a Part D add-on of $91.00. That separate-filing table is not gentle. It arrives with steel-toe boots. Before a Roth conversion, write down your filing status. Then write down the relevant IRMAA bracket. Then write down how much room you have before the next threshold. That room is your Medicare premium buffer.

A simple example

Imagine a single Medicare beneficiary with projected Medicare MAGI of $105,000 before any Roth conversion. The first 2026 individual IRMAA threshold is above $109,000. That person has roughly $4,000 of room before the first IRMAA tier. A $3,000 taxable Roth conversion may stay below the threshold. A $10,000 taxable Roth conversion may push income above it. Once the threshold is crossed, the effect is not limited to the dollars above the line. The premium tier applies based on the bracket. In the first tier, Part B would be the standard $202.90 plus $81.20 per month. If the person also has Part D coverage, Part D would add $14.50 per month to the plan premium. That is $95.70 per month of extra Medicare premium exposure in the first tier. Over 12 months, that is $1,148.40. Now compare that with the tax benefit of the conversion. Maybe the conversion still wins. Maybe it does not. The point is not that Roth conversions are bad. The point is that a $10,000 conversion is not always just a $10,000 conversion. Sometimes it is a tax move plus a Medicare premium move. That is the part calculators love to hide in a footnote. Footnotes are where budgets go to get humbled.

Why the timing feels weird

SSA says it uses the most recent federal tax return the IRS provides. For 2026 IRMAA, SSA says this is generally a return filed in 2025 for tax year 2024. That means a 2024 conversion can affect 2026 Medicare premiums. A 2025 conversion may affect a later premium year. A 2026 conversion may affect a later premium year after that. The lag matters for retirement planning. Someone may convert at age 63 and see Medicare premium consequences around age 65. Someone already on Medicare may convert this year and see the adjustment later when SSA receives the tax return data. This is why the conversion year and the premium year are not always the same year. It also explains why people say, “But my income is lower now.” They may be right. Medicare may still be looking backward. SSA does provide paths to update or challenge certain income information. But a voluntary Roth conversion is not automatically a life-changing event. That distinction matters.

What counts in Medicare MAGI

SSA says Medicare MAGI is your total adjusted gross income plus tax-exempt interest income. AGI is not the same thing as taxable income after deductions. This is a common planning mistake. People look at their taxable income after the standard deduction and think they have more room than they do. IRMAA does not start from taxable income after the standard deduction. It starts from MAGI as SSA defines it for Medicare premium purposes. That means ordinary income items can matter. IRA distributions can matter. Pension income can matter. Capital gains can matter. Taxable brokerage dividends can matter. Social Security taxation can matter indirectly because the conversion can make more Social Security benefits taxable. Tax-exempt interest can matter because SSA adds it back. That last one surprises municipal bond investors. Tax-exempt does not always mean invisible. It just means tax-exempt for a specific tax calculation. Medicare has its own guest list. And IRMAA is standing at the door with a clipboard.

Roth conversions are still allowed at high income

IRS Topic 309 says you may be able to convert amounts from a traditional IRA into a Roth IRA regardless of the amount of your adjusted gross income. That is important because Roth contribution limits and Roth conversion rules are different animals. High income can limit direct Roth IRA contributions. High income does not automatically block a Roth conversion. So the issue is usually not, “Am I allowed to convert?” The issue is, “What does the conversion do to my tax return?” IRS Topic 309 also says conversions after 2017 from a traditional IRA to a Roth IRA may not be recharacterized. Publication 590-A says the same thing for conversions made in tax years beginning after December 31, 2017. That means you generally cannot undo a completed traditional-to-Roth conversion by recharacterizing it back. This is a big planning point. Old internet advice about undoing a conversion may be stale. Stale tax advice is like stale bread. Sometimes harmless. Sometimes it breaks a tooth.

The premium impact checklist

Start with filing status. Single, married filing jointly, and married filing separately can produce very different IRMAA thresholds. Do not use the joint table if you file separately. Do not use the separate table if you file jointly. This sounds obvious. It is exactly the kind of obvious thing people skip when the spreadsheet looks pretty. Next, estimate Medicare MAGI before the conversion. Use AGI plus tax-exempt interest as the Medicare starting point. Do not subtract the standard deduction. Do not subtract itemized deductions. Do not subtract the conversion income just because it is a Roth planning worksheet. IRS Publication 590-A warns that conversion income is not subtracted when figuring other AGI-based phaseouts and taxable income. Then identify the nearest 2026 IRMAA threshold. For many individual filers, the first line is $109,000. For many joint filers, the first line is $218,000. For married filing separately, the jump after $109,000 is especially sharp. Now calculate conversion room. Conversion room equals the next IRMAA threshold minus projected Medicare MAGI before conversion. If the number is negative, you are already in an IRMAA tier. If the number is small, one tidy conversion can move you. Then test multiple conversion sizes. Test $0. Test a small conversion that stays within the bracket. Test a conversion that fills the bracket. Test the conversion your advisor originally suggested. Test the conversion that creates the best tax bracket outcome. Compare all of them after Medicare premiums. Finally, check the calendar. Ask which tax year the conversion belongs to. Ask which Medicare premium year may use that tax return. Ask whether you are already on Medicare or approaching enrollment. The closer you are to Medicare, the less imaginary IRMAA becomes.

The $1 mistake near a threshold

IRMAA thresholds are cliffs, not smooth ramps. That means crossing a threshold by a small amount can raise monthly premiums for the tier. A person who is $1 below a threshold and a person who is $1 above a threshold may face different premium treatment. That can feel unfair. It is also exactly why the math matters. If a conversion puts you barely above a threshold, you need to know that before December 31. After the conversion is completed, the recharacterization escape hatch is generally not available for post-2017 traditional IRA conversions. You may still manage estimated taxes. You may still plan later years. But the income event may already be baked. This is why year-end Roth conversion planning should include more than one number. Do not only ask, “How much room do I have in the 22% bracket?” Ask, “How much room do I have before Medicare premiums jump?” Ask, “Will the conversion make more Social Security taxable?” Ask, “Will capital gains or mutual fund distributions arrive later in December?” Ask, “Do I have tax-exempt interest that SSA adds back?” Ask, “Is this the year to convert, or should I spread the conversion?” The bracket cliff does not care that you were busy. It has no customer service department.

Married couples need a second pass

Married filing jointly gets wider IRMAA thresholds than single filing. That sounds comfortable. But retirement creates strange income years. One spouse may retire before the other. One spouse may start Social Security. One spouse may begin Medicare while the other is still working. One spouse may have a pension start date. One spouse may have a large traditional IRA. One spouse may die, and the survivor may later file as single. That last point is uncomfortable, but it is real planning. Joint thresholds are not simply doubled forever in every life scenario. A Roth conversion strategy that looks reasonable for a couple may need a survivor-income test. This does not mean converting everything immediately. It means measuring the future tax and Medicare shape. For joint filers, the first 2026 threshold is above $218,000. The next threshold is above $274,000. A large conversion can cross more than one line. Crossing one line may be acceptable. Crossing two lines accidentally is a different flavor of spicy. Financial planning should be flavorful. It should not require a fire extinguisher.

Married filing separately is its own warning label

SSA’s 2026 married filing separately table is much less forgiving. If you are married, lived with your spouse at some time during the taxable year, and file separately, SSA lists only three rows. At MAGI up to $109,000, the standard Part B premium applies. Above $109,000 and less than $391,000, the listed Part B add-on is $446.30 per month. The listed Part D add-on is $83.30 per month. At $391,000 or more, the listed Part B add-on is $487.90 per month. The listed Part D add-on is $91.00 per month. That is not a tiny nudge. That is a monthly bill with a megaphone. If you file separately, do not borrow assumptions from articles written for joint filers. Do not rely on generic conversion advice that says “fill the bracket” without checking IRMAA. Do not assume separate filing solves everything because it helped one unrelated tax issue. Separate filing can be useful in some cases. It can also be expensive in Medicare premium planning. This is professional-advice territory. Bring the actual filing status. Bring the projected return. Bring the conversion amount. Bring snacks. The meeting may have spreadsheets.

What to do before a Roth conversion

First, pull last year’s federal tax return. Find adjusted gross income. Find tax-exempt interest. Find IRA distribution lines and taxable IRA distribution amounts. Find capital gains. Find Social Security benefit taxation if applicable. Next, build a current-year estimate. Add wages if you still work. Add pension income. Add taxable IRA withdrawals. Add brokerage income. Add expected capital gains. Add mutual fund year-end distributions if you can estimate them. Add tax-exempt interest for the Medicare MAGI test. Then add the proposed Roth conversion. If the conversion is from a traditional IRA with no basis, the taxable amount may be close to the converted amount. If you have nondeductible basis, Form 8606 and pro-rata rules can matter. This article is not the place to freestyle basis math. That is how spreadsheets start speaking in tongues. Ask your tax professional before assuming only part of the conversion is taxable. Then compare the estimate to the SSA IRMAA table. Look at the next threshold. Look at the one after that. Large conversions can pass more than one line. Finally, set aside cash for taxes outside the IRA if possible. Withholding from the conversion may reduce the amount that actually reaches the Roth. Underpayment rules may also matter. IRS Publication 590-A notes that if you must include conversion income, you may need to increase withholding or make estimated tax payments. The conversion decision should include tax payment logistics. Good planning is not glamorous. It is often just avoiding a very avoidable invoice.

What to do after an IRMAA notice arrives

Medicare.gov says the Social Security IRMAA notice tells higher-income households about Medicare Part B and Part D premium adjustments for the coming year. Medicare.gov says the notice is sent by Social Security. If you receive the notice, keep it. Check the tax year used. Check the MAGI listed. Check the filing status. Check whether SSA used the correct return. SSA says that for 2026 IRMAA it generally uses tax year 2024, from a return filed in 2025. If SSA used older tax data and you filed a newer return, SSA says you can call or visit a local Social Security office so records can be updated. If you amended your tax return and the amendment changes the income counted for IRMAA, SSA says to let them know. SSA says it will need a copy of the amended return and IRS acknowledgment receipt. If your income went down because of a listed life-changing event, SSA says Form SSA-44 may be used to request a reduction. SSA lists events such as marriage, divorce, death of a spouse, work stoppage or reduction, certain loss of income-producing property, certain pension plan changes, and certain employer settlement payments. The key phrase is life-changing event. A planned Roth conversion by itself is usually not the same as stopping work or losing pension income. So do not assume SSA-44 will erase a conversion-driven IRMAA increase. It might help if a qualifying event also reduced income. It is not a universal undo button. Government forms rarely do magic. They mostly do paperwork with better shoes.

When a Roth conversion may still be worth it

Paying IRMAA does not automatically make a Roth conversion a mistake. Sometimes the conversion still wins after counting premiums. That can happen if future tax rates are expected to be higher. It can happen if future required minimum distributions would be large. It can happen if a surviving spouse would face higher single-filer tax brackets later. It can happen if heirs would inherit a large taxable IRA under compressed distribution rules. It can happen if the taxpayer has a low-income year before Social Security, pension income, or RMDs begin. It can happen if the conversion fills a tax bracket without crossing a Medicare threshold. It can happen if crossing one IRMAA tier now prevents a much larger problem later. The goal is not to avoid IRMAA at all costs. The goal is to avoid accidental IRMAA. There is a difference. Intentional premium cost can be part of a good strategy. Accidental premium cost is just tuition paid to the school of “oops.” The best conversion plan shows the trade-off clearly. Income tax this year. Medicare premium effect later. Future RMD reduction. Future Roth flexibility. Survivor filing-status risk. Estate and beneficiary goals. Liquidity for the tax bill. Those items belong in one decision, not six separate vibes.

When to slow down

Slow down if your estimated MAGI is within $5,000 of an IRMAA threshold. Slow down if you file married filing separately. Slow down if you are 63 or older and about to enter Medicare. Slow down if you are already on Medicare and your income varies year to year. Slow down if you have large mutual fund distributions in taxable accounts. Slow down if you sold a home, business, or concentrated stock position. Slow down if you have municipal bond interest. Slow down if you are receiving Social Security and the conversion may make more benefits taxable. Slow down if your spouse has different Medicare timing. Slow down if this is the first year after retirement. Slow down if you are converting just because someone online said “tax rates will only go up.” Maybe they will. Maybe they will not. Your Medicare bill arrives in real dollars either way. Planning should be humble enough to handle both.

A practical conversion worksheet

Use this worksheet before you approve the conversion. Line 1: expected adjusted gross income before conversion. Line 2: expected tax-exempt interest. Line 3: Medicare MAGI before conversion, which is line 1 plus line 2. Line 4: proposed taxable Roth conversion. Line 5: Medicare MAGI after conversion, which is line 3 plus line 4. Line 6: filing status. Line 7: next IRMAA threshold for that filing status. Line 8: distance to threshold before conversion. Line 9: distance to threshold after conversion. Line 10: expected Part B premium tier. Line 11: expected Part D IRMAA tier if enrolled in drug coverage. Line 12: estimated annual Medicare premium increase. Line 13: estimated federal income tax from the conversion. Line 14: estimated state income tax from the conversion, if applicable. Line 15: expected long-term benefit from lower future taxable IRA balance. Line 16: cash source for the tax bill. Line 17: confidence level in the income estimate. Line 18: notes for professional review. If line 17 is low, do not pretend the answer is precise. Use ranges. Run a small conversion. Wait for year-end distribution estimates. Or split conversions across years. The best answer is sometimes “not yet.” That answer is boring. Boring saves money suspiciously often.

Common mistakes

Mistake 1: using taxable income instead of Medicare MAGI. IRMAA starts from AGI plus tax-exempt interest, not taxable income after deductions. Mistake 2: forgetting Part D. Even if the Part B premium gets most of the attention, IRMAA can also apply to Medicare prescription drug coverage. Mistake 3: ignoring the two-year lookback. For 2026 IRMAA, SSA generally looks to tax year 2024 data. Mistake 4: assuming Roth conversions can still be recharacterized. IRS says post-2017 traditional-to-Roth conversions cannot be recharacterized. Mistake 5: treating all MAGI definitions as the same. Roth contribution MAGI and Medicare MAGI are not identical planning concepts. Mistake 6: forgetting tax-exempt interest. SSA adds tax-exempt interest to AGI for Medicare MAGI. Mistake 7: planning only around federal tax brackets. The best federal bracket plan can still create an ugly Medicare premium result. Mistake 8: converting before checking capital gains. A December mutual fund distribution can push an otherwise clean plan over the line. Mistake 9: assuming SSA-44 fixes everything. SSA-44 is tied to specified life-changing events and income reduction, not every planned income spike. Mistake 10: waiting until after the conversion to ask the question. That is the financial planning version of checking the weather after the picnic.

FAQ

Does a Roth conversion count for IRMAA?

It can. The taxable part of a Roth conversion can increase AGI. SSA’s Medicare MAGI definition starts with AGI and adds tax-exempt interest. If the conversion pushes Medicare MAGI over an IRMAA threshold, premiums may rise.

Which income year affects 2026 IRMAA?

SSA says 2026 IRMAA generally uses the most recent federal tax return the IRS provides. For 2026, SSA says that is generally a return filed in 2025 for tax year 2024. SSA may use 2023 data if that is the newest data available.

What is the 2026 standard Part B premium?

Medicare.gov and SSA list the 2026 standard Part B premium as $202.90 per month. The amount can be higher based on income. The amount can also be affected by separate late enrollment penalties in some cases. This article is focused on IRMAA, not late enrollment penalties.

What is the first 2026 IRMAA threshold?

For most individual filing statuses, SSA lists the first 2026 threshold as MAGI above $109,000. For married filing jointly, SSA lists the first threshold as MAGI above $218,000. Married filing separately has a separate table. Always use the table that matches the return you file.

Does IRMAA affect both Part B and Part D?

Yes, it can. SSA says higher-income beneficiaries may pay an additional premium amount for Part B and Medicare prescription drug coverage. If you have only one of those benefits, SSA says you pay IRMAA only on the benefit you have. If you have both, the adjustment can apply to both.

Can I appeal IRMAA after a Roth conversion?

You can disagree with SSA’s decision if the information is wrong. SSA also provides a process for certain life-changing events that reduce income. A planned Roth conversion alone is not listed as a life-changing event. If SSA used incorrect tax data, amended return data, or older IRS data, follow SSA’s instructions for updating the record.

Can I undo a Roth conversion if it triggers IRMAA?

Generally, do not count on that. IRS Topic 309 and Publication 590-A say conversions after 2017 from a traditional IRA to a Roth IRA may not be recharacterized. That is why the IRMAA check needs to happen before the conversion. The planning window is usually before the income event, not after the notice.

Is avoiding IRMAA always the right move?

No. A conversion can still be worth doing even if it creates IRMAA. The question is whether the long-term benefit exceeds the income tax and premium cost. Avoiding every premium increase can lead to under-converting in genuinely good tax years. The enemy is not IRMAA. The enemy is surprise IRMAA.

Should I convert before Medicare starts?

Maybe. Some people convert in lower-income years before Medicare begins. But the Medicare lookback can still matter near age 63 and later. If you are close to Medicare age, model which tax year may feed which premium year. Do not assume “before Medicare” means “invisible to Medicare.”

Who should review the numbers?

A CPA, enrolled agent, retirement-focused financial planner, or SHIP counselor can help. The best reviewer is someone who understands both tax returns and Medicare premium rules. Bring the proposed conversion amount and the relevant SSA table. Do not show up with only a vibe and a coffee. Coffee is useful. It is not documentation.

Sources

Bottom line

A Roth conversion can be good tax planning and still raise Medicare premiums later. Those two statements can live in the same room. For 2026, the key numbers are the $202.90 standard Part B premium, the $109,000 individual IRMAA threshold, and the $218,000 married filing jointly threshold. The key mechanism is Medicare MAGI. The key mistake is checking ordinary income tax while ignoring Part B and Part D. Before converting, estimate AGI, add tax-exempt interest, add the taxable conversion, and compare the result with the SSA IRMAA table. Then decide whether the conversion is still worth it. If yes, do it intentionally. If no, resize it. That is the whole point. The conversion should be a choice, not a premium surprise with stationery.