All premium, surcharge, and tax figures reflect the 2026 program year, using 2024 modified adjusted gross income under Medicare’s two-year lookback. This article is educational and not individualized tax, legal, or investment advice.
TL;DR — Quick Verdict
- A Roth conversion counts as ordinary income and inflates your modified adjusted gross income (MAGI), the exact figure Medicare uses to set your Income-Related Monthly Adjustment Amount (IRMAA) two years later.
- In 2026 the standard Part B premium is $202.90/month, but a large conversion can push you to $689.90/month per person — a difference of $5,844 a year, before Part D.
- IRMAA is a cliff, not a phase-in: converting $1 over a threshold triggers the full surcharge for the whole year. Tier 1 costs about $1,148/year per person; Tier 5 costs about $6,936/year per person.
- Timing beats size. Converting to the top of the 24% federal bracket ($211,400 MAGI for joint filers) while watching the $218,000 IRMAA line is the core planning tension.
- Verdict: For most married retirees under age 63, a measured multi-year conversion strategy beats one large conversion — it fills low tax brackets without detonating an IRMAA cliff.
The Centers for Medicare & Medicaid Services set the 2026 standard Part B premium at $202.90 a month. A retiree who converts $150,000 from a traditional IRA to a Roth in a single year can watch that same premium climb to $689.90 — more than triple — two years down the road. The trigger is not wealth; it is one number on one tax return. Roth conversions are taxed as ordinary income, and that income flows straight into the MAGI figure the Social Security Administration reads to assign your IRMAA surcharge. A conversion executed in 2024 sets your 2026 Medicare bill, long after the cash has moved and the decision is irreversible. This guide shows the exact 2026 IRMAA brackets from CMS, models what a conversion does to a real couple’s premiums, compares the one-big-conversion approach against a staged multi-year plan, and names the mistakes that cost retirees thousands. Vanguard and Fidelity will happily process the conversion in minutes; neither warns you about the Medicare invoice that arrives in 2026.
The 2026 IRMAA Brackets: What a Conversion Actually Costs
IRMAA is a surcharge layered on top of the standard Part B and Part D premiums once your MAGI crosses a threshold. For 2026, MAGI equals your adjusted gross income plus tax-exempt interest, pulled from your 2024 return. A Roth conversion adds dollar-for-dollar to that AGI, so it can lift you one, two, or three tiers depending on size.
The table below shows every 2026 tier as published by CMS. The income ranges are your 2024 MAGI; the premiums are what each person pays monthly in 2026. These are per-beneficiary figures — a married couple where both spouses are on Medicare pays each amount twice.
Source: Centers for Medicare & Medicaid Services, 2026 Medicare Parts A & B Premiums and Deductibles fact sheet, published November 14, 2025 (verify at cms.gov). Single-filer thresholds are half the joint amounts shown.
Single filers hit the first cliff at $109,001. The mechanics are identical to the way NIIT surtax rules and avoidance strategies layer an extra levy on top of ordinary rates — except IRMAA reprices a fixed monthly premium rather than taxing the marginal dollar.
How a Conversion Moves Your MAGI: A Worked Scenario
Consider a married couple, both 66 and enrolled in Medicare, with $150,000 of baseline 2024 income from Social Security, a pension, and required minimum distributions. That figure sits comfortably below the $218,000 first IRMAA threshold, so absent any conversion they would each pay the standard $202.90 in 2026.
Now they convert $120,000 from a traditional IRA to a Roth in 2024. The conversion is fully taxable as ordinary income, lifting their MAGI to $270,000. That lands them in the second IRMAA tier for 2026. Each spouse’s Part B premium jumps from $202.90 to $284.10, and each now owes a $14.50 Part D surcharge where they previously owed nothing.
Run the annual math. The Part B increase is $81.20 per month per person, and the Part D surcharge adds $14.50 per month per person — $95.70 combined. Across twelve months that is $1,148.40 per person, or $2,296.80 for the couple. The couple converted $120,000 and, as a side effect they never saw on the conversion confirmation screen, bought themselves a $2,296.80 Medicare surcharge that recurs for the full 2026 year. Push the conversion to $210,000 and MAGI reaches $360,000, landing them in the fourth tier at $527.50 each — a $7,783.20 combined annual premium versus the $4,869.60 they would pay at baseline.
The lookback makes this worse than it sounds. By 2026, when the bill arrives, the conversion income is two years gone. Retirees routinely forget the 2024 decision entirely and appeal a surcharge they cannot appeal, because a voluntary Roth conversion is not one of the qualifying life-changing events on Form SSA-44.
The Cliff Effect: Why $1 Can Cost $2,296
Ordinary income tax is marginal. Cross into the 24% bracket and only the dollars above the line are taxed at 24%; everything below keeps its lower rate. IRMAA works nothing like that. It is a cliff. The moment your MAGI touches $218,001 as a joint filer, the entire surcharge for that tier applies to every month of the year — there is no gradual phase-in.
Picture two couples with nearly identical returns. The first reports $218,000 in 2024 MAGI and pays the standard $202.90 each in 2026. The second reports $218,001 — one dollar more — and each spouse pays $284.10 plus the $14.50 Part D surcharge. That single dollar costs the second couple $2,296.80 over the year. No investment on earth returns a worse ratio than one dollar of income triggering $2,296.80 of surcharge.
This is why a Roth conversion demands the same threshold discipline that governs capital gains rates by holding period and income: the goal is not merely to convert cheaply but to stop the conversion before it nudges MAGI across the next cliff. A conversion sized to land at $217,900 is dramatically cheaper in total cost than one landing at $218,100, even though the taxable conversion amounts differ by only $200. The discipline here mirrors the precision required in tax-loss harvesting mechanics and real savings, where the exact dollar figure realized determines the benefit.
One Large Conversion vs. Staged Multi-Year Conversions: Which Is Better?
The central strategic choice is whether to convert a large balance in a single year or spread smaller conversions across several years. Each approach trades off differently against the federal bracket schedule and the IRMAA cliff.
A single large conversion front-loads the tax bill and almost always breaches one or more IRMAA thresholds. Convert $300,000 in one year on top of $150,000 of baseline income and your MAGI hits $450,000 — the fifth IRMAA tier at $649.20 per person, plus $83.30 Part D each. You also push a large slice of the conversion through the 32% and 35% federal brackets, since the 24% bracket for joint filers ends at $211,400 in 2026.
A staged approach converts a smaller amount annually — say $55,000 a year for six years — keeping each year’s MAGI near the top of the 22% bracket ($100,800 for joint filers) and well under the $218,000 IRMAA line. Total tax paid is lower because more dollars are taxed at 22% and 24% instead of 32%, and IRMAA is avoided entirely in years the threshold is respected. The trade-off is time and market risk: the un-converted balance stays exposed to future required minimum distributions and possible rate increases. This account-by-account sequencing is the heart of asset location strategy across account types.
Verdict
For most married retirees under age 63 — before the two-year lookback reaches their first Medicare year — staged conversions win. They fill the 22% and 24% brackets deliberately while keeping MAGI under $218,000, avoiding both higher marginal rates and every IRMAA cliff. A single large conversion only makes sense when a specific event (a large future RMD, an inheritance, or an expected rate hike) makes concentrating the tax hit into one lower-income year genuinely cheaper than spreading it. Model both before converting a dollar.
What Most People Get Wrong About Conversions and IRMAA
Three mistakes recur often enough that planners treat them as predictable.
Mistake 1: Ignoring the two-year lookback near age 63
A conversion at age 63 sets your premium at 65; a conversion at 63 or 64 lands in your first Medicare years. The consequence is an IRMAA surcharge that greets you the moment you enroll. The correct action is to complete aggressive conversions before the calendar year you turn 63, so the lookback window has cleared by the time Medicare begins.
Mistake 2: Forgetting that both spouses pay
Retirees model IRMAA as a single premium and are stunned when the surcharge doubles. Every tier figure applies per Medicare-enrolled person. The consequence is a real cost of $2,296.80 rather than $1,148.40 at Tier 1. The correct action is to multiply every surcharge by the number of enrolled spouses when sizing a conversion.
Mistake 3: Overlooking tax-exempt interest in MAGI
Municipal bond interest is federally tax-free but still counts toward IRMAA MAGI. A retiree holding a large muni portfolio may sit closer to a threshold than their tax return’s taxable income suggests. The consequence is a conversion that breaches a cliff the investor never saw coming. The correct action is to add tax-exempt interest to projected AGI before deciding how much to convert. For high earners still working, the interaction with a backdoor Roth IRA process for high earners compounds the MAGI-tracking challenge.
Is a Roth Conversion Worth the IRMAA Hit? Conditional Logic
The surcharge is a real cost, but it is not automatically disqualifying. Whether a conversion pays off depends on your situation.
A conversion is likely worth accepting an IRMAA surcharge when your current marginal rate is meaningfully lower than the rate you expect in retirement, when large future required minimum distributions would otherwise force you into a high bracket anyway, or when you are converting primarily to leave tax-free assets to heirs who would face their own high rates. In these cases a one- or two-year IRMAA surcharge is a finite, calculable price for permanently removing an asset from future taxation. Because inherited Roth assets sidestep the ordinary-income drag entirely, the calculus connects directly to step-up in basis for inherited assets and broader estate tax planning tools, costs, and savings.
A conversion is likely not worth the hit when it merely accelerates income you would have realized at the same or lower rate anyway, when the surcharge recurs across multiple years because you convert too much too fast, or when you are within the two-year lookback of enrolling and could simply wait. Charitably inclined retirees have a further lever: routing appreciated assets through a donor-advised fund costs and tax benefits vehicle can lower MAGI in the same year, partially offsetting a conversion’s IRMAA impact. The distinction between converted ordinary income and portfolio income also mirrors the broader investment vs earned income tax treatment that shapes every retirement withdrawal plan.
Frequently Asked Questions
Does a Roth conversion always increase my Medicare premium?
No. IRMAA applies only when your MAGI crosses a threshold — $218,000 for joint filers or $109,000 for single filers in 2026. A conversion that keeps you below the first cliff produces no surcharge at all. The 2026 standard Part B premium of $202.90 stands until your 2024 MAGI exceeds the entry threshold, per CMS.
Can I appeal an IRMAA surcharge caused by a conversion?
Generally no. The Social Security Administration lets you appeal using Form SSA-44 only after a qualifying life-changing event — marriage, divorce, work stoppage, or death of a spouse. A voluntary Roth conversion is not on that list, so the surcharge stands for the year it applies. This is why conversion timing matters more than the appeal process.
How far ahead should I plan conversions before Medicare?
Because of the two-year lookback, income in the year you turn 63 sets your premium at 65. Retirees who want to convert aggressively without triggering IRMAA typically complete large conversions before age 63. After that, each conversion should be sized against the $218,000 joint threshold to avoid a surcharge in your Medicare years.
What’s the most a conversion could cost me in 2026 IRMAA?
The top 2026 tier applies at $750,000 joint MAGI: $689.90 Part B plus $91.00 Part D per person monthly. Against the standard $202.90, that is roughly $6,936 more per person for the year, or nearly $14,000 for a couple both on Medicare. A single very large conversion is the most common way retirees reach this tier.
How We Researched This Article
Every premium, surcharge, and income threshold in this article was verified against primary sources before publication. The 2026 IRMAA brackets, the standard Part B premium of $202.90, and the $283 annual deductible come directly from the Centers for Medicare & Medicaid Services 2026 Medicare Parts A & B Premiums and Deductibles fact sheet, released November 14, 2025 and effective January 1, 2026. The tier-by-tier Part B and Part D surcharge amounts were cross-checked against the CMS release as reported by Kiplinger and Medicare.org, which reproduce the official schedule.
Federal tax bracket thresholds and the $32,200 married-filing-jointly standard deduction used in the conversion scenarios are drawn from IRS Revenue Procedure 2025-32, published October 9, 2025, and confirmed against the Internal Revenue Service newsroom release and the Tax Foundation annual bracket summary. The two-year lookback mechanics and MAGI definition follow SSA program guidance (POMS HI 01101.020).
The couple scenarios are modeled, not measured: they apply the verified 2026 brackets to hypothetical income profiles to illustrate the cliff effect and staged-conversion trade-offs. Annual surcharge totals are original calculations multiplying the monthly Part B and Part D figures by twelve, and by two where both spouses are enrolled. One limitation applies: 2027 and 2028 IRMAA brackets were not final at the time of research, so multi-year conversion planning should be re-run each fall as CMS releases updated thresholds. State-level premium variation is outside this article’s scope. Research last conducted July 2026. All figures were verified against named primary sources before publication.