Roth Conversion and IRMAA: How It Affects Medicare Premiums

Yes. The taxable amount of a Roth conversion is added to your adjusted gross income, which feeds the modified adjusted gross income (MAGI) Social Security uses to set IRMAA. The effect is delayed: a conversion done in 2026 generally shows up in your 2028 Part B and Part D premiums, and it only costs you something if it pushes MAGI over an IRMAA threshold. Social Security treats an IRA conversion as one-time income, not a life-changing event, so it isn't grounds for relief on Form SSA-44.

Rules and figures are checked against Social Security's operating manual (POMS), Section 1839 of the Social Security Act, CMS's 2026 premium announcement and IRS guidance, all listed under Sources. Every example on this page is hypothetical.

A Roth conversion counts toward IRMAA because the converted amount is taxable income in the year you convert. The IRS says you include in gross income anything you'd have had to include if you hadn't converted it, normally on the return for the conversion year (IRS Publication 590-A, conversions). Rolling a traditional 401(k) or 403(b) balance into a Roth IRA is treated the same way.

From there, the path is short. The taxable amount lands with your IRA distributions on Form 1040, rolls into adjusted gross income, and becomes part of the number Social Security compares with the IRMAA thresholds.

IRMAA MAGI = adjusted gross income (Form 1040, line 11; line 11a on the 2025 form) + tax-exempt interest (line 2a)

That's the definition in Social Security's MAGI policy, POMS HI 01101.010, and it covers most retirees. The statute behind it also adds back a few rare exclusions, such as excluded foreign earned income (Social Security Act §1839(i)(4)). Our guide on how to calculate MAGI for IRMAA line by line covers those.

Three details decide how much of a conversion actually reaches that number.

Only the taxable part counts

If you've ever put after-tax (nondeductible) money into a traditional IRA, part of a conversion may be a return of that basis, which isn't included in income. Form 8606 figures the split pro rata across all your traditional, SEP and SIMPLE IRAs, so you can't choose to convert only the after-tax dollars. A $40,000 conversion doesn't always mean $40,000 of MAGI.

It can add more than dollar for dollar

For many converters, 85% of their Social Security benefits are already taxable, the maximum. Then a $50,000 conversion adds $50,000 to MAGI and no more.

At more modest incomes, it's different. The IRS decides how much of your benefit is taxable by adding half your benefits to all your other income, including tax-exempt interest (IRS Publication 915). A conversion raises that total, so it can pull more of your Social Security into AGI. MAGI then rises by more than the amount you converted.

Deductions don't shrink it

IRMAA stops at AGI plus tax-exempt interest. The standard deduction and itemized deductions come after AGI, so they lower your tax bill without lowering IRMAA MAGI. The same goes for the new deduction of up to $6,000 for people 65 and older, available for 2025 through 2028, which is also taken after AGI (IRS: deductions for working Americans and seniors). Municipal bond interest you never paid federal tax on goes right back in.

Seven distinctions that trip up converters

Social Security generally sets your premiums from the tax return two years before the premium year, and never more than three (POMS HI 01101.010). So a conversion's IRMAA effect lands two years after the year you convert. Convert in 2026, and the question is your 2028 Medicare bill.

That lag has three practical consequences.

The increase usually lasts one premium year

Each premium year is priced from its own tax year. If a 2026 conversion pushes you over a line but your 2027 income stays under it, 2029 premiums are set from 2027 and the surcharge drops away. A conversion plan spread over several years can still produce several IRMAA years: one for each conversion year that crosses a line.

Your first exposed year is usually the year you turn 63

If you enroll at 65, your first premium year generally looks back to the tax year in which you turned 63. Conversions in earlier years usually fall outside the Medicare window. That's why the years before 63 get so much attention from people planning large conversions.

Two things shift the window. Enrolling in Part B later, for example because you're covered through current work, moves your first premium year later. And the three-year fallback described below can occasionally reach back one more year.

You're planning against lines that don't exist yet

CMS released the 2026 figures on November 14, 2025, and normally announces the next year's in the fall. As of October 17, 2026, it hadn't announced 2027's. Its own Medicare & You 2027 handbook still prints the 2026 thresholds and notes that 2027 amounts weren't available when it went to print. The 2028 thresholds that will judge a 2026 conversion are further off still.

The law indexes the lower thresholds to consumer prices and rounds them to the nearest $1,000 (Social Security Act §1839(i)(5)). Social Security's table shows the joint line rising from $194,000 for 2023 to $218,000 for 2026. The same section schedules the top single-filer threshold, $500,000 since 2019, to start adjusting with 2028. Using the 2026 lines as a stand-in is reasonable. Planning to the dollar against them isn't.

IRMAA isn't phased in gradually. It's a set of tiers, and one dollar over a threshold puts you in the higher tier for the entire premium year. In 2026, crossing the first line adds $81.20 a month to Part B and $14.50 a month to Part D: $1,148.40 for the year for one person with both.

IRMAA is added to the $202.90 standard Part B premium and to whatever your Part D plan charges, in Original Medicare and Medicare Advantage alike. Part D IRMAA applies only if you have Medicare drug coverage. The single column also covers head of household and qualifying surviving spouse; married filing separately uses a steeper table (see edge cases). Annual figures are the monthly amounts times 12. Sources: SSA POMS HI 01101.020; SSA, Premiums: Rules for Higher-Income Beneficiaries.

Next to a conversion, that structure makes the last few thousand dollars the most expensive ones.

Suppose a single filer expects $100,000 of MAGI before converting and converts $15,000. MAGI lands at $115,000, which is $6,000 over the line. Under 2026 figures, that $6,000 slice triggers $1,148.40 of extra premiums, about 19 cents per dollar, before any income tax. Converting $9,000 instead would have stopped at exactly $109,000, still in the standard tier.

The reverse also holds: once you're over a line, the surcharge doesn't grow until the next one. A single filer pays the same 2026 surcharge at $110,000 as at $137,000. Each further step adds about $1,735 a year per person with Part B and Part D, except the top step, which adds $580.80.

That's why some people who decide to cross a threshold convert up to the top of the tier rather than just past the line. Whether that makes sense depends on your tax bracket and long-term plan. It's a conversation for a tax professional, not a premium table.

It's October 2026. One spouse is 67 and has been on Medicare since 2024. The other is 64 and will enroll in 2027. They file jointly and want to move part of a traditional IRA into a Roth before December 31. Here's their expected 2026 income before any conversion.

1. Name the premium year. 2026 income sets 2028 premiums. By 2028, both spouses are on Medicare. This year only one of them gets a Medicare bill. The year their conversion is judged, both will.

2. Find the room. Using the 2026 joint threshold of $218,000 as a stand-in for 2028: $218,000 − $128,800 = $89,200.

3. Check the Social Security effect. Their benefits are already 85% taxable, the maximum. So every dollar they convert adds exactly one dollar of MAGI.

4. Price the options. The table and chart below apply the 2026 tiers to five conversion amounts.

Going from $85,000 to $100,000 adds $2,296.80 of premiums for the couple. Measured against the $10,800 that crossed the line, that's about 21 cents per dollar, on top of income tax.

A $145,000 conversion costs the same IRMAA as $100,000. The extra $45,000 moves into the Roth with no additional Medicare cost. Income tax on it is a separate question.

Going from $145,000 to $150,000 adds $3,472.80 of premiums for $5,000 more converted. That's roughly 69 cents per dollar of the extra conversion.

If they'd priced the decision from this year's bill, with only one spouse on Medicare, they'd have seen $1,148.40 at the first tier. The real exposure in 2028 is twice that.

They also wouldn't plan to the last dollar. An $85,000 conversion leaves $4,200 of room against today's line. That's thin if a fund pays a large December distribution or dividends come in higher than expected, and the 2028 line itself is unknown.

None of these amounts is the "right" one. A couple might reasonably choose $145,000 if the future tax savings they expect outweigh $2,296.80 of premiums. That trade-off belongs with someone who can see their whole tax picture. What the arithmetic does is make the Medicare cost visible before it's locked in.

Not on the grounds of the conversion. Social Security's operating manual lists "conversion of an IRA" as one-time income that is a non-qualifying event, alongside capital gains from selling property, lottery winnings and cashing bonds (POMS HI 01120.005, Life Changing Events). The list of events that can support a new determination is exclusive.

The events that do qualify are short and specific: death of a spouse, marriage, divorce or annulment, work reduction, work stoppage, loss of income-producing property, loss of employer pension, and a settlement payment from a current or former employer. If someone asks anyway, Social Security's staff instructions say to explain that the event doesn't qualify. A request filed regardless is recorded as a non-qualifying event and dismissed. You can still request reconsideration of the IRMAA decision itself, but the conversion gives the rules nothing to act on.

Two different procedures get called an "IRMAA appeal"

A request for a new initial determination asks Social Security to use more recent income because a qualifying life-changing event lowered it. Form SSA-44 is the usual way to ask, though you can also call or make an appointment (SSA: Request to lower IRMAA). It isn't a formal appeal.

A reconsideration is the formal appeal, filed on Form SSA-561-U2 within 60 days of receiving your notice. Social Security presumes you received it five days after the date on the notice (POMS HI 01140.001). It's for a decision you believe is wrong, such as the wrong MAGI or filing status. You can file both at once, though Social Security notes that a new determination usually gets the same result without an appeal.

Sources: SSA, Premiums: Rules for Higher-Income Beneficiaries; POMS HI 01120.005 and HI 01140.001.

The last row is the one most converters overlook. A conversion can't qualify you, but it doesn't disqualify you either. If you stopped working, for instance, retirement counts as a work stoppage on Form SSA-44, and that event is judged on its own terms.

The first years after retirement are a popular time to convert. Wages have stopped and required distributions haven't started. Those are often the same years a retiree asks Social Security to replace an old, salary-heavy return with newer income.

The catch is that both decisions use the same number. A new initial determination looks at the MAGI for the newer year, all of it. Social Security's manual says it doesn't develop the types of income that make up MAGI, only that MAGI decreased after the event (POMS HI 01120.005). A conversion in that newer year is inside the figure.

None of this means retirees shouldn't convert. It means the conversion and the SSA-44 request should be planned together. In practice, that can mean sizing the conversion so the newer year still clears the line you're asking Social Security to use, or doing the larger conversion in a year that isn't part of the request. A tax professional can tell you what that costs on the tax side.

You sign an SSA-44 request under penalty of perjury, so any estimate has to include income you actually expect, conversions included. The form also lets you give a second estimate for the following year, and a conversion you've planned for that year belongs in it (POMS HI 01120.005). Our step-by-step SSA-44 guide for retirees covers which tax year to enter and what proof to attach.

Work through these steps in order before money moves, because a conversion can't be reversed once it's done.

What to gather before you run the numbers

• Last year's Form 1040, especially lines 2a, 4b, 5b, 6b and 11 (11a on the 2025 form), as a baseline
• This year's statements from your brokerage, pension and Social Security
• Any Form 1099-R from IRA withdrawals or conversions earlier this year
• Form 8606, if you've ever made nondeductible IRA contributions
• Your latest IRMAA notice, which shows the tax year and MAGI Social Security used
• Part B and Part D start dates for you and your spouse
• If you're at RMD age, this year's required amount and whether it's been taken

Bring in help where the question belongs. A CPA or tax-focused financial planner can size a conversion against your tax brackets and state taxes. Social Security (1-800-772-1213) answers questions about your notice. Your State Health Insurance Assistance Program (SHIP) helps with Medicare coverage questions.

You file late or on extension

Social Security uses the most recent return the IRS can provide: usually two years back, never more than three (POMS HI 01101.010). The law's cutoff is October 15 of the year before the premium year; if the IRS doesn't have the two-year-old return in usable form by then, the older one is used until it does (Social Security Act §1839(i)(4)(B)). A return filed on extension can miss that date. When that happens, a conversion year can be used twice, or a conversion made at 62 can reach your first Medicare year. If Social Security used an older return and you've since filed the newer one, it says to call or visit and it will update its records.

You're already taking required minimum distributions

Your RMD age depends on your birth year. Under the SECURE 2.0 Act, it's 73 if you were born from 1951 through 1959 and 75 if you were born in 1960 or later (26 U.S.C. §401(a)(9)(C)(v)). The statute's wording overlaps for people born in 1959; IRS proposed regulations issued in July 2024 treat that group as 73. If you were born before 1951, your RMDs started under earlier rules.

In any year you owe an RMD, that amount can't be converted. The IRS says you can't convert amounts that must be distributed for that year, including the year you reach your RMD age (IRS Publication 590-A). The RMD is taxable income, so it uses up room under the line before any conversion starts. If you delay your first RMD to April 1 of the following year, as the IRS allows, two RMDs land in that second year (IRS: RMD FAQs).

If you're 70½ or older, a qualified charitable distribution sent straight from the IRA to a charity is excluded from income and can count toward the RMD, which leaves more room under the line (IRS Publication 590-B).

You file married filing separately

If you lived with your spouse at any point in the year, a much steeper table applies. In 2026, MAGI over $109,000 and under $391,000 goes straight to $446.30 a month of Part B IRMAA and $83.30 of Part D; at $391,000 or more it's $487.00 and $91.00 (POMS HI 01101.020). If you lived apart the entire year, the regular single table applies.

The younger spouse has Marketplace coverage

If the spouse who isn't on Medicare yet buys an ACA Marketplace plan, the same conversion can affect premium tax credits in the conversion year itself. Marketplace savings use expected income for the coverage year and a different MAGI that also adds non-taxable Social Security (HealthCare.gov: what to include as income). The expanded credits that ran through 2025 have expired, so in 2026 household income above 400% of the federal poverty line generally ends eligibility for the credit entirely (IRS: eligibility for the premium tax credit). Near that line, a conversion can cost far more in lost Marketplace credits than in Medicare premiums.

You're 65 or older between 2025 and 2028

The new deduction of up to $6,000 per person 65 or older phases out as income rises above $75,000, or $150,000 on a joint return (IRS). It doesn't change IRMAA, but a conversion that raises AGI can shrink it. That's a tax cost on top of any premium cost, and worth including when you size a conversion.

Your filing status changes later

Below the top tier, the 2026 joint thresholds are twice the single ones: $218,000 against $109,000. A conversion done in a year you file jointly, including the year a spouse dies, is measured against the joint lines. In later years a surviving spouse usually files as single, and the household's income is then measured against lines half as high. Death of a spouse is itself a qualifying life-changing event (how IRMAA relief works after the death of a spouse), but it doesn't change which lines later years are measured against.

If you're planning a conversion this year, work through the sequence above with your own numbers and leave a cushion. Then have a tax professional weigh the bracket trade-off before December 31, since conversions are normally taxed in the year you make them.

If a notice already reflects a conversion year, compare the MAGI on it with line 11 plus line 2a of that year's return. If the numbers match and nothing else changed, the surcharge generally runs for that premium year, and the next notice uses the next return.

If you also retired, cut back, married, divorced, lost a spouse or lost pension income, that event, not the conversion, is what may let Social Security use newer income. That's the question CheckIRMAA's free check is built to answer.

• SSA POMS HI 01101.010, Modified Adjusted Gross Income (MAGI): MAGI definition, two-year lookback, three-year limit, 2023–2026 thresholds
• SSA POMS HI 01101.020, IRMAA Sliding Scale Tables: 2026 Part B and Part D amounts, married-filing-separately table
• SSA POMS HI 01120.005, Life Changing Events: qualifying events, non-qualifying one-time income including IRA conversions, second-year estimates
• SSA POMS HI 01140.001, Overview of the Appeals Process for the Income-Related Monthly Adjustment Amount: 60-day reconsideration window, appeal levels, appeal vs. new determination
• SSA, Premiums: Rules for Higher-Income Beneficiaries: 2026 premium table, amended returns, older-return updates, IRS data errors
• SSA, Request to lower an IRMAA: Form SSA-44 and other ways to ask
• Social Security Act §1839: MAGI add-backs, threshold indexing and rounding, the taxable year used and the October 15 data cutoff
• CMS, Medicare & You 2027: still lists 2026 IRMAA thresholds; 2027 amounts not available at printing
• CMS, 2026 Medicare Parts A & B Premiums and Deductibles: $202.90 standard Part B premium, released November 14, 2025
• IRS Publication 590-A (2025): conversion income in the conversion year, RMDs that can't be converted, no recharacterization since 2018
• IRS Publication 590-B (2025): qualified charitable distributions count toward the RMD
• IRS, Retirement plan and IRA required minimum distributions FAQs: first-RMD deadline of April 1 of the following year
• 26 U.S.C. §401(a)(9)(C)(v): RMD applicable age of 73 or 75
• IRS, IRA FAQs: Recharacterization: conversions and Roth rollovers since 2018 can't be recharacterized
• IRS Publication 915 (2025): how much of Social Security is taxable
• IRS, Roth IRAs: qualified distributions are tax-free
• IRS, One Big Beautiful Bill Act: tax deductions for working Americans and seniors: deduction for people 65 and older, 2025–2028
• HealthCare.gov, What to include as income: Marketplace MAGI
• IRS, Eligibility for the premium tax credit: the 400% of poverty line income limit

This article explains federal rules in general terms as of October 17, 2026. It isn't tax, legal or financial advice, and it can't predict how Social Security will decide a request. CheckIRMAA is independent of the Social Security Administration, CMS and Medicare.