IRMAA Surcharges Explained: The Medicare Cliff That Penalizes Roth Conversions

The $50,000 Roth Conversion That Cost $4,237 in Medicare Surcharges

A 66-year-old single retiree converts $70,000 from a traditional IRA to a Roth in 2024. On paper, it's a clean tax move. Her marginal federal rate is 22%, she pays roughly $15,400 in federal tax on the conversion, and the dollars now grow tax-free for life. Her advisor models the conversion in a standard tax projection and confirms the math.

Two years later, in 2026, she opens her Medicare letter and discovers her Part B and Part D premiums have jumped sharply. The conversion she made in 2024 lifted her 2024 MAGI from $98,000 to $168,000 — past three IRMAA thresholds, landing her $1,000 over the Tier 3 cutoff for single filers. Her Medicare premiums are now $353.10 per month higher than they would have been: about $4,237 in additional Medicare premiums for the 2026 calendar year alone.

That $4,237 wasn't in the original tax model. It's not a tax — it's a Medicare premium surcharge — and it's invisible to most tax software. It's also a one-year cost for what was supposed to be a permanent benefit, so amortized over a 25-year retirement the math still works in her favor. But the surcharge is real, it came as a surprise, and it points to a structural mechanic in retirement planning that catches a remarkable number of otherwise-careful households.

That mechanic is IRMAA — the Income-Related Monthly Adjustment Amount. It's the Medicare program's way of charging higher-income beneficiaries more for the same Part B and Part D coverage, and it operates through one of the most punitive cliff-bracket structures in all of federal tax-and-transfer law.

What IRMAA Actually Is

IRMAA stands for Income-Related Monthly Adjustment Amount. It's a surcharge added to standard Medicare Part B (doctor visits, outpatient care) and Part D (prescription drug) premiums when a beneficiary's MAGI exceeds certain thresholds.

The base 2025 Part B premium is $185.00 per month. A beneficiary in the top IRMAA tier pays $628.90 per month for Part B — plus an additional $85.80 per month Part D surcharge layered on top of whatever their Part D plan already costs. That's a difference of roughly $529.70 per month per person, or about $6,357 per year per person, between the standard premium and the top tier. For a married couple both on Medicare, the household impact doubles.

IRMAA was created by the Medicare Modernization Act in 2003 (Part B) and the Medicare Improvement for Patients and Providers Act in 2010 (Part D). It's administered by the Social Security Administration, with brackets published annually by the Centers for Medicare & Medicaid Services. The statutory authority sits in 42 U.S.C. §1395r(i) for Part B and 42 U.S.C. §1395w-113(a)(7) for Part D — both meaningful for advisors who want to point clients to the underlying rules.

The thing that makes IRMAA distinct from ordinary federal income tax — and what generates most of the planning failures around it — is its cliff-bracket structure and its two-year lookback.

The Cliff Structure: $1 Over a Threshold, Entire Next Tier

Federal income tax brackets are progressive: each marginal dollar of income is taxed only at the rate that applies to that specific dollar. If a married couple files jointly and their taxable income is $1 over the 22% bracket threshold, only that one dollar is taxed at 22%; the rest stays in the lower brackets below it.

IRMAA does not work that way. IRMAA brackets are cliffs.

If a single filer's MAGI is $106,001, they pay the entire Tier 1 surcharge for the year. If it's $106,000, they pay no surcharge. The difference between those two MAGI figures is one dollar. The difference in annual Medicare premiums is over $1,000 per person. This is not a marginal penalty; it's a step function. The entire next tier of surcharges applies for the full year, retroactively, based on a tax return filed two years prior.

The 2025 CMS-published IRMAA schedule looks like this (the schedule that determines Medicare premiums paid in calendar year 2025, based on the 2023 tax return):

These thresholds and dollar amounts are updated annually. Brackets are inflation-indexed for most tiers but Tier 5 has historically been a fixed cliff at $500K single / $750K MFJ for several years. Always verify current-year numbers against ssa.gov/medicare/lower-irmaa before planning.

The Two-Year Lookback: Why Today's Conversion Hits Two Years From Now

The other defining feature of IRMAA is the two-year lookback. The MAGI used to determine the IRMAA tier in any given Medicare year is taken from the federal tax return filed two years prior.

• 2026 IRMAA → based on 2024 tax return MAGI
• 2027 IRMAA → based on 2025 tax return MAGI
• 2028 IRMAA → based on 2026 tax return MAGI

The reason is administrative: SSA needs a finalized, IRS-confirmed MAGI figure to apply the surcharge, and by the time Medicare premiums for year N are set in late year N-1, only the year N-2 return has been processed.

This lookback creates a planning rhythm that often gets overlooked. Decisions made in tax year N drive Medicare premiums in calendar year N+2. A retiree who converts a large IRA balance to a Roth in 2024 sees the IRMAA consequences in 2026. A retiree who realizes a large capital gain in 2025 sees the IRMAA consequences in 2027.

For couples coordinating Roth conversions with their Medicare-eligibility year, the lookback can either help or hurt. A 63-year-old who converts aggressively in 2024 will have age-65 Medicare premiums in 2026 set by that 2024 MAGI — meaning the conversion year directly determines the first IRMAA tier the household lands in. Pre-Medicare conversions are not a free zone; they set up the surcharge two years out.

What Counts as MAGI for IRMAA

Different federal programs use different definitions of MAGI. The IRMAA definition is one of the broadest.

IRMAA MAGI = AGI (Form 1040, line 11) + tax-exempt interest (Form 1040, line 2a)

That's it. Unlike MAGI for Roth IRA contribution phase-outs or ACA premium credits, IRMAA does not add back items like the foreign earned income exclusion, student loan interest deduction, or US savings bond interest exclusion for education. The simplicity is also what makes it punitive: virtually any income source that lands in AGI lands in IRMAA MAGI.

Income sources that count toward IRMAA MAGI:

• Wages, self-employment income, and net rental income
• Pension and annuity income (taxable portion)
• Traditional IRA, 401(k), 403(b), and TSP distributions, including RMDs
• Roth conversions (dollar-for-dollar)
• Taxable Social Security benefits
• Realized capital gains (long-term and short-term)
• Qualified dividends and ordinary dividends
• Taxable interest
• Tax-exempt municipal bond interest (added back specifically for IRMAA)
• Inherited IRA distributions, including those required under the SECURE Act 10-year rule

Income sources that do not count toward IRMAA MAGI:

• Roth IRA and Roth 401(k) qualified distributions
• HSA qualified distributions
• Return of cost basis from non-deductible IRA contributions
• Loans (including reverse mortgage proceeds and policy loans from permanent life insurance cash value)
• Inheritances (the inheritance itself is not income; subsequent distributions from inherited tax-deferred accounts do count)
• Gifts received
• Life insurance death benefits

This list explains why "tax-free" accounts have such an outsized role in late-retirement planning. A Roth distribution doesn't just save federal income tax — it also avoids feeding IRMAA, the Social Security taxation tier structure, and the ACA premium credit phase-out. The compound effect is much larger than the headline tax savings.

The Income Events That Most Often Trigger IRMAA

In practice, a small number of planning events generate the majority of unexpected IRMAA surcharges. Knowing which ones tend to land where helps advisors flag the risk early.

Roth conversions. Dollar-for-dollar, conversions land in MAGI. A conversion sized without an IRMAA model attached frequently lands a household in a tier higher than the marginal federal tax savings can justify. This is the single most common avoidable IRMAA event.

First-year RMDs. The required minimum distribution starting age (currently 73, rising to 75 in 2033 under SECURE 2.0) introduces a step-up in MAGI that many retirees do not see coming. A household that lived comfortably under Tier 1 for years can flip into Tier 2 or 3 simply because RMDs began.

Sale of a primary residence with appreciation above the §121 exclusion. The exclusion is $250,000 single / $500,000 MFJ. Any gain above that amount lands in AGI as a long-term capital gain — taxed at preferential federal rates, but counted at full face value for IRMAA. A retired couple selling a long-held home in a high-appreciation market routinely sees a one-time MAGI spike into Tier 4 or 5.

Inherited IRA distributions under the SECURE Act 10-year rule. A non-spouse beneficiary inheriting a traditional IRA must drain it within 10 years. Compressed into a working spouse's earnings years or a high-income retirement year, the distributions can land the household in a top IRMAA tier for multiple years.

Realized capital gains. Long-term gains are taxed at preferential rates federally, but for IRMAA they count at the same face value as ordinary income. A portfolio rebalance, a concentrated-position sale, or a mutual fund's large year-end capital gain distribution all land in MAGI.

Pension lump sums rolled to an IRA and then withdrawn. The rollover itself is not taxable, but any subsequent withdrawal hits AGI. Retirees who take a lump sum and then draw heavily from the IRA in the rollover year see a compounded IRMAA effect.

Annuity withdrawals exceeding cost basis. Non-qualified annuity distributions are taxed under last-in-first-out (LIFO) ordering, meaning early withdrawals are gain-first and fully count toward IRMAA.

The Effective IRMAA Rate on a Marginal Dollar

The most useful framing for IRMAA planning is the effective IRMAA rate — the additional Medicare premium cost divided by the income event that triggered it, expressed as a percentage.

Worked example: A married couple's baseline 2024 MAGI is $200,000, which puts them just under the Tier 1 threshold of $212,000 for the 2026 IRMAA year — base premiums only. They consider a $70,000 Roth conversion, which would push 2024 MAGI to $270,000. That lands them in 2026 Tier 2 (which begins at $266,000 MFJ), crossing two tier boundaries at once.

• Baseline (under Tier 1 threshold) surcharge over standard, per person, annual: $0
• Tier 2 surcharge over standard, per person, annual: ~$2,646
• Increase per person from moving Standard → Tier 2: ~$2,646
• Both spouses on Medicare: ~$2,646 × 2 = ~$5,292

That ~$5,292 of additional Medicare premium is the cost of the $70,000 conversion crossing two tier boundaries. The effective IRMAA rate on the conversion is $5,292 / $70,000 = about 7.6%, layered on top of the federal and state marginal income tax on the conversion. A 22% federal marginal bracket combined with a 7.6% IRMAA cost makes the effective marginal cost of the conversion roughly 29.6% — before state tax.

The same effective-rate framing applies to capital gains, RMDs, and any other discretionary income event. The point isn't to avoid all conversions, gains, or distributions. It's to right-size them to land just under the next tier ceiling whenever a tier crossing is discretionary.

The RetirementForge IRMAA Calculator computes this effective IRMAA rate directly, comparing the IRMAA tier with and without a proposed conversion and outputting the per-dollar cost. The Roth Calculator extends this across a multi-year horizon, sizing each year's conversion to a chosen tier ceiling.

The Life-Changing Event Appeal (Form SSA-44)

The two-year lookback can produce a result that feels deeply unfair: a retiree whose income has dropped substantially in retirement still pays surcharges based on a working year's MAGI. SSA recognizes this through the Life-Changing Event appeal.

Filing Form SSA-44 allows a beneficiary to request that SSA use a more recent (or projected) MAGI in place of the two-year-old tax return MAGI. Qualifying life-changing events include:

• Retirement or work stoppage (the most common — by definition, retirement triggers an income drop relative to working years)
• Work reduction
• Marriage, divorce, or death of spouse
• Loss of pension income (e.g., underfunded pension plan failure)
• Loss of income-producing property due to disaster
• Receipt of a settlement payment from a former employer for involuntary termination

The appeal is most valuable in the year the retiree first enrolls in Medicare, when the two-year lookback would otherwise pin Medicare premiums to the last full year of working income. A retiree who earned $250,000 in 2024 and retires January 2026 would, without an appeal, pay 2026 Medicare premiums based on 2024 MAGI — likely in Tier 2 or 3 — even though current retirement income is far lower. Form SSA-44 lets SSA use the 2026 projected MAGI instead.

The form is short (two pages), but it requires documentation of the life-changing event (typically a letter from the former employer or a pension termination notice). It can be submitted before or after Medicare premiums are set, with retroactive adjustment when filed before the year ends.

This is not a recommendation to file — appeals are subject to SSA's review and approval, and not every income drop qualifies. Beneficiaries with questions about their specific situation should consult their Medicare counselor or a qualified financial advisor before filing.

Coordinating IRMAA with the Rest of the Plan

IRMAA isn't a standalone calculation. It interacts with — and frequently competes against — several other planning surfaces.

Federal tax brackets. A conversion that fills the 22% bracket without crossing an IRMAA tier may be optimal. A conversion that fills the 22% bracket and crosses into IRMAA Tier 2 may not be. The right comparison is the total marginal cost (federal + state + IRMAA), not just the federal bracket fill.

Social Security taxation tiers. The provisional income calculation for taxation of Social Security has its own bracket-like structure with cliffs at $25K/$32K (single/MFJ) for 50% taxation and $34K/$44K for 85% taxation. Income events that don't trigger IRMAA may still push more of Social Security into taxable territory.

ACA premium tax credits (for pre-65 retirees). For couples retiring before 65, MAGI controls Affordable Care Act subsidy eligibility. A pre-Medicare year with a large conversion can wipe out ACA subsidies entirely — often a larger immediate cost than IRMAA would have been on the same conversion in a Medicare year.

Capital gain harvesting. Realized gains feed IRMAA at face value even though they're taxed federally at 0%, 15%, or 20%. A retiree taking advantage of the 0% LTCG bracket may still pay IRMAA on those gains two years later.

The right way to think about IRMAA is not as a single isolated bracket schedule, but as one of several cliff-style cost structures that a retiree's MAGI passes through in any given year. Roth conversions, RMDs, and capital gain realizations should be modeled against the full stack — federal tax, state tax, IRMAA, Social Security taxation, ACA — not against any single one.

What This Means for Retirement Income Planning

Three practical takeaways for advisors and retirees working through IRMAA-sensitive planning:

1. Build the IRMAA model in before the tax model. Tax software defaults to federal and state brackets and rarely surfaces IRMAA at all. Adding a step that maps projected MAGI against current-year IRMAA brackets — and the future-year impact through the two-year lookback — should be a standard part of any conversion, harvesting, or distribution decision.

2. Treat tier ceilings as hard caps, not targets. Discretionary income events should land just below the next tier ceiling, not at it. The cliff structure means there's no benefit to being closer to the threshold — and a small forecasting error in either direction has asymmetric consequences.

3. Use the SSA-44 appeal aggressively in the transition year. The year of retirement is the most common cause of an unjustified IRMAA charge. Beneficiaries don't have to accept the surcharge silently. The appeal is administrative, documented, and well-understood by SSA.

The broader point is that retirement income planning is a coordination problem, and IRMAA is one of the most under-modeled coordination surfaces in the field. A conversion strategy that ignores IRMAA can quietly leak thousands of dollars per year in Medicare premiums for retirees who would have considered themselves well-planned. The math doesn't have to be complex — but the model has to include the IRMAA dimension, and most don't.

For advisors building this into their workflow, the IRMAA Calculator handles single-year tier mapping with the effective-rate output, and the Roth Calculator extends the analysis across a multi-year conversion horizon with the two-year lookback applied automatically. The companion article Withdrawal Sequencing: Which Accounts to Tap First covers how IRMAA interacts with the broader drawdown order.

IRMAA isn't a tax. It isn't progressive. It isn't kind to retirees whose income temporarily spikes. But it is predictable — and what's predictable can be planned for. The households that get hurt by IRMAA are almost always the households whose advisors didn't model it. That's a planning problem, not a Medicare problem.

This article is for educational purposes only and is not tax, legal, or investment advice. IRMAA brackets, premium amounts, and rules change annually. Consult a qualified tax professional and verify current-year IRMAA brackets at ssa.gov/medicare/lower-irmaa before making any financial decision based on this material.