IRMAA and Roth Conversions: The Tax Cliff Every Pre-Retiree Must Navigate (2026)

You've heard that the years between retirement and RMDs are your best window to convert traditional IRA money to Roth — low tax brackets, earned income gone, Social Security not yet started. That's true. But there's a second tax system layered on top of the federal brackets that most people discover too late: IRMAA.

IRMAA (Income-Related Monthly Adjustment Amount) is a Medicare surcharge that can add up to $13,872/year for a couple — triggered not by current income, but by a Roth conversion you did two years ago. For retirees doing multi-year conversion plans, IRMAA thresholds matter as much as tax brackets.

What IRMAA is and how it works

Medicare Part B (medical insurance) and Part D (prescription drug) premiums include a standard amount everyone pays. But once your income crosses certain thresholds, you pay an income-related surcharge on top — IRMAA. The SSA determines your IRMAA each year using your MAGI from two years prior.

IRMAA applies whether you're on Original Medicare or Medicare Advantage. Part B participation is required in either case, so the Part B surcharge is unavoidable once you're in an IRMAA tier. The Part D surcharge applies to prescription coverage — even if you get drug coverage through a Medicare Advantage plan, you still pay the Part D IRMAA surcharge.

2026 IRMAA tiers — based on your 2024 MAGI

For 2026, the SSA uses your 2024 Modified Adjusted Gross Income (MAGI). The standard Part B premium in 2026 is $202.90/month. Here are the tiers and what each costs:¹²

Part D surcharge is per person and per plan year. Annual extra = (Part B + Part D surcharge) × 12 per Medicare enrollee.

The two-year lookback — the planning timeline that trips people up

IRMAA uses a two-year-old return because that's the most recent year the IRS has processed and shared with the SSA. This creates a specific planning horizon:

• Your 2026 IRMAA is based on your 2024 MAGI — if you retired in 2024 and income dropped, you may still be in a high IRMAA tier in 2026 based on your last working year.
• Conversions done in 2026 affect your 2028 Medicare premiums — not 2026. The cost of crossing a tier lands two years later.
• The optimal conversion window often starts 2–3 years after retirement — once the two-year lookback clears your high-income working years.

Why IRMAA is a cliff, not a bracket

Federal income tax brackets work incrementally: the first dollar of income in a bracket is taxed at that rate, and only income above the bracket threshold moves up. IRMAA doesn't work that way.

IRMAA is a threshold surcharge. Cross the line by $1 and you owe the full tier surcharge on every dollar of Medicare premiums for the entire year. There's no partial surcharge, no gradual phase-in.

This creates extreme marginal cost at each tier boundary. For a married couple with both spouses on Medicare:

• $1 over $218,000 → $2,296/year more in Part B + Part D premiums
• $1 over $274,000 → $3,474/year more (the difference between Tier 1 and Tier 2 for two people)
• $1 over $342,000 → another $3,470/year jump

In practice, this means the $218K and $274K MFJ thresholds are "invisible brackets" with marginal rates well above 100% on the dollars immediately above them. Converting $50,000 and landing $2,000 over the $218K line costs $2,296 in Medicare surcharges the following two years — on top of the federal income tax on the $50,000.

Strategic conversion ceilings: staying under each tier

Before calculating your optimal conversion amount, you need to know your "other MAGI" — income that will show up on that year's return regardless of conversions:

• Pension and annuity income
• Social Security (85% is typically taxable once combined income exceeds certain thresholds)
• Required Minimum Distributions (if you're past RMD age)
• Dividends, capital gains, rental income
• Part-time work or self-employment

Subtract that "other MAGI" from the IRMAA threshold you want to stay under — the difference is your maximum conversion amount without crossing the tier.

Example: Retired couple, MFJ, both on Medicare. Other MAGI: $95,000 (pension $60K + 85% of Social Security $35K). Target: stay under $218,000 (Tier 0).

Maximum conversion = $218,000 − $95,000 = $123,000

If their traditional IRA balance is $1.5 million and they're doing a 10-year conversion plan, they need to average $150K/year. That $123K ceiling means they may need to accept Tier 1 in some years — or push the plan slightly longer — or use capital gain harvesting to reduce other MAGI in the years they convert most heavily.

Use the IRMAA-aware Roth conversion calculator to run this math automatically for your numbers and see each tier scenario side by side.

When is crossing an IRMAA tier worth it?

The cliff is real, but sometimes crossing it is still the right call. The breakeven question: does the lifetime tax saved by converting more outweigh the IRMAA surcharge triggered?

A rough framework: if you're converting at 22% now to avoid 32% on future RMDs, you're saving 10 cents per dollar converted. The IRMAA Tier 1 surcharge for a couple is $2,296/year — paid for two years (it resets after two years when the lookback catches up). That's $4,592 in additional Medicare cost per IRMAA event.

To justify crossing into Tier 1, the extra conversion that pushed you over the line should save at least $4,592 in lifetime tax. At a 10% bracket differential, that means converting at least $46,000 above the tier boundary — not just $1 over. A more complete analysis includes time-value of money, state taxes, and beneficiary outcomes, but this directional test filters out marginal overshoot scenarios quickly.

Multi-year IRMAA planning: the conversion calendar

For a retiree with a large traditional IRA doing conversions over 8–12 years, IRMAA is a rolling constraint, not a one-year problem. Each year's conversion amount determines Medicare premiums two years later — which is itself a tax-year constraint when you're also converting that year.

A multi-year IRMAA-aware plan typically works like this:

1. Year 0–2 post-retirement: IRMAA may still reflect high-income working years via lookback. Convert conservatively or not at all while the lookback clears.
2. Year 3–10 (golden window): IRMAA lookback reflects retirement income. Maximize conversions while staying under your target tier, or accept a specific tier deliberately if the math supports it.
3. Year 11+ / RMD years: RMD income stacks on top of conversion income. Conversion room shrinks as RMDs grow. IRMAA exposure increases. Many advisors shift strategy to QCDs and charitable giving instead of additional conversions at this stage.

This sequence is exactly why the golden window matters — the 8–12 years when IRMAA lookback is lowest and RMDs haven't started is the highest-value conversion window.

Social Security and the IRMAA double-exposure

Social Security creates a specific IRMAA interaction that surprises many retirees. When combined income (half of SS + other income including conversions) exceeds $44,000 (MFJ), 85% of SS benefits become taxable. Conversion income stacks directly on top.

But that's separate from IRMAA. IRMAA uses MAGI — which includes the taxable portion of Social Security. So in a year where you have $40K in SS (85% taxable = $34K), a pension of $30K, and you convert $150K:

• MAGI = $34K + $30K + $150K = $214,000 (under the $218K MFJ Tier 1 threshold — barely)
• If you had converted $155K instead: $219,000 MAGI → Tier 1 IRMAA triggered for 2028

Delaying Social Security creates additional conversion room: before SS starts, you have only pension + investment income + conversions counting toward MAGI. The years between retirement and SS claiming are often when the IRMAA window is widest. See the SS + Roth conversion guide for the full interaction analysis.

Married couples: two IRMAA exposure points

When both spouses are on Medicare, IRMAA is assessed individually but based on joint MAGI. Both pay Part B and Part D surcharges at the tier determined by the couple's combined MAGI — which is why the couple-tier numbers in the table above are exactly double the per-person figures.

Several planning nuances matter for couples:

• Age difference: If one spouse is 5+ years younger and not yet on Medicare, you have only one IRMAA exposure — the Medicare-eligible spouse. This can allow more aggressive conversions in those years.
• Death of spouse: Filing status shifts from MFJ to single. The MFJ threshold of $218K becomes $109K single — half the room, same income. A surviving spouse with $130K annual income would be in Tier 1 instead of Tier 0. Pre-planning conversions while both spouses are alive (MFJ) is part of the widow bracket strategy.
• Separate Medicare enrollment timing: If one spouse is under 65, their Part B doesn't exist yet — no IRMAA surcharge for that person. IRMAA applies only once enrolled in Medicare.

The IRMAA appeal: SSA-44 and life-changing events

This is the most overlooked piece of IRMAA planning. If your income dropped significantly due to a qualifying event — and you're being assessed IRMAA based on an older, higher-income year — you can appeal to use more recent income.

The SSA accepts a "life-changing event" appeal via Form SSA-44. Qualifying events include:³

• Marriage or divorce
• Death of a spouse
• Work stoppage (retirement)
• Work reduction
• Loss of income-producing property (not due to negligence)
• Loss of pension income or employer settlement payment

If you retired in 2024 (work stoppage event) and your 2026 IRMAA is based on your 2024 working income, you can file SSA-44 and provide an estimated or actual 2025 return showing your lower retirement income. The SSA can then reassess your 2026 IRMAA at your current income level rather than the two-year-old working income.

If your appeal is denied, you have additional recourse: request a hearing before an Administrative Law Judge, appeal to the Medicare Appeals Council, or petition in federal district court. Most IRMAA appeals based on legitimate life-changing events succeed at the initial reconsideration stage without requiring formal hearings.

Proactive strategy: Advisors helping recently retired clients routinely file SSA-44 as soon as the lower-income year's return is available — it's a free, low-effort way to recover thousands in Medicare surcharges during the transition years.

IRMAA-optimized Roth conversion planning requires multi-year modeling

The complexity here — two-year lookbacks, cliff mechanics, Social Security interactions, RMD growth projections, state taxes on conversions — is precisely why the retirees who get the most value from Roth conversions work with specialists rather than running year-at-a-time numbers.

A well-structured plan models:

• Year-by-year MAGI projections including all income sources
• Which IRMAA tier you'll land in each year based on this year's conversion — and two years' future premiums
• Whether accepting a tier surcharge in a given year is cost-positive after lifetime NPV
• When to file SSA-44 as the lookback clears high-income working years
• How QCDs at 70½+ can reduce IRMAA exposure while meeting charitable goals

Use the IRMAA-aware conversion calculator to model specific conversion amounts against each tier threshold, or the lifetime NPV calculator for multi-year scenario modeling. Then connect with an advisor to build the full plan.

Frequently asked questions

Does IRMAA apply to Medicare Advantage?

Yes. IRMAA is assessed on Part B and Part D regardless of plan type. If you're on Medicare Advantage, you still pay the Part B IRMAA surcharge. The Part D surcharge applies to whatever prescription coverage you have.

What if I only have Part B and no Part D plan?

You pay the Part B surcharge only. The Part D surcharge applies only if you're enrolled in a Part D plan or Medicare Advantage with drug coverage.

Does IRMAA affect Roth conversions after RMDs begin?

Yes — and it becomes harder to manage. RMD income is fixed (based on prior year-end account balance), so it stacks on top of conversions. Most retirees have less conversion room once RMDs begin, and IRMAA exposure is higher. Some shift from conversions to QCDs at that point to keep MAGI down. See the 2026 Roth conversion rules for the RMD-first requirement.

Can I reduce IRMAA by using a QCD instead of converting?

QCDs (Qualified Charitable Distributions) reduce MAGI directly — they satisfy RMD obligations without the distribution appearing in MAGI at all. For charitably inclined retirees, QCDs can lower IRMAA exposure significantly. In 2026, the annual QCD limit is $111,000 per person.⁴

How far in advance should I plan for IRMAA?

At least two years, because of the lookback. Ideally, a full projection for the golden window years — showing MAGI in each year, which IRMAA tier it triggers, and how each year's conversion decision cascades into future premiums.

Sources

1. CMS: 2026 Medicare Parts A & B Premiums and Deductibles — 2026 Part B base premium $202.90; IRMAA Part B surcharges per tier.
2. SSA POMS HI 01101.020: IRMAA Sliding Scale Tables (updated 12/2025) — 2026 IRMAA income thresholds and surcharge amounts for Parts B and D.
3. SSA: Request to lower an Income-Related Monthly Adjustment Amount (IRMAA) — qualifying life-changing events and SSA-44 process.
4. IRS Rev. Proc. 2025-67: 2026 inflation adjustments — QCD limit $111,000 for 2026.

IRMAA thresholds and surcharge amounts verified against CMS and SSA POMS. Values apply to 2026 Medicare premiums based on 2024 MAGI. Part D surcharges are per enrollee and vary if enrolled in a standalone Part D plan vs. Medicare Advantage with drug coverage. QCD limit verified against IRS Rev. Proc. 2025-67. Page last reviewed May 2026.