IRMAA Cliff at $103K: Roth Conversion Targeting Below the Bracket

One dollar of income over $103,000 in 2024 modified adjusted gross income triggers approximately $1,050 to $1,100 in additional annual Medicare premiums in 2026 for a single filer. For a married couple filing jointly on Medicare, exceeding $206,000 by one dollar doubles that to roughly $2,100 to $2,200. This is the IRMAA cliff — the Income-Related Monthly Adjustment Amount — and it is not a gradual slope. It is a hard step function where a single dollar of excess income produces the full surcharge for the entire calendar year. If you are managing Roth conversions, RMD timing, or withdrawal sequencing from a six-figure retirement portfolio, the IRMAA bracket is the constraint you must size every conversion against.

How the two-year lookback works

Medicare determines your IRMAA tier using your MAGI from two years prior. Your 2024 tax return sets your 2026 premiums. Your 2025 return sets 2027 premiums. The Social Security Administration pulls this data automatically from IRS records — you do not need to report it, and you cannot opt out.

IRMAA MAGI is defined as your adjusted gross income (Form 1040, line 11) plus tax-exempt interest income (line 2a). This includes all the income sources you would expect — pension distributions, traditional IRA withdrawals, Roth conversion amounts, capital gains, rental income, and the taxable portion of Social Security — plus one source many retirees overlook: municipal bond interest. If you hold $300,000 in muni bond funds yielding 3.5%, that $10,500 in tax-exempt interest adds to your IRMAA MAGI even though it does not appear in your AGI. IRMAA MAGI does not add back untaxed Social Security benefits, which distinguishes it from ACA MAGI used for marketplace premium subsidies.

2026 IRMAA bracket table (based on 2024 MAGI)

The following table shows the 2026 IRMAA tiers based on 2024 MAGI, with the approximate monthly Part B premium at each tier. Part D surcharges are separate and vary by plan, but Tier 1 adds approximately $13.70/month per person.

Source: CMS Medicare premiums and IRMAA thresholds. Part B figures shown are approximate for 2026 based on 2024 MAGI. Part D surcharges ($13.70 to $81.00/month at Tier 1 through Tier 5) are additional and vary by plan. Thresholds are indexed to inflation and updated annually by CMS.

The $103,000 cliff: exact dollar math

Consider a single filer — a 66-year-old retiree — with the following 2024 income: $24,000 Social Security benefit (approximately $20,400 taxable at the 85% inclusion rate), $32,000 pension from a former employer, $8,000 in qualified dividends and capital gains from a taxable brokerage account, and $3,500 in municipal bond interest. Before any IRA distribution or Roth conversion, this retiree’s IRMAA MAGI is approximately $63,900 ($20,400 + $32,000 + $8,000 + $3,500).

The headroom below $103,000 is $39,100. This retiree can convert up to $39,100 from a traditional IRA to a Roth IRA in 2024 without triggering any IRMAA surcharge on 2026 premiums. A conversion of $39,101 — one dollar over — triggers the full Tier 1 surcharge: approximately $888 in additional Part B premiums plus roughly $164 in Part D surcharges, totaling approximately $1,052 in extra annual Medicare costs from that single excess dollar.

At Tier 2 ($129,001 single), the Part B surcharge jumps to $2,220/year. This means a retiree who overshoots $103,000 by $26,001 pays $1,332 more in Part B alone compared to someone who landed at $103,000. The marginal cost of each additional IRMAA tier is steep enough that precise conversion sizing — not rounding to the nearest $10,000 — produces measurable annual savings.

Roth conversion sizing: the targeting framework

The goal is to convert as much traditional IRA balance to Roth as possible each year without crossing the next IRMAA bracket. This reduces future RMDs (which are calculated only on traditional balances), shifts assets into a tax-free account with no lifetime RMDs, and avoids the IRMAA surcharge that a larger conversion would trigger. The framework has four steps:

1. Project your non-conversion MAGI. Add up all income sources for the year: taxable Social Security, pension, rental income, dividends, capital gains, required minimum distributions (if applicable), and tax-exempt interest. Use prior-year figures as a baseline, adjusted for known changes (e.g., a new RMD, Social Security COLA increase).
2. Identify the target IRMAA threshold. For most retirees near the first bracket, this is $103,000 (single) or $206,000 (MFJ) based on the applicable tax year. If your non-conversion MAGI already exceeds the first tier, target the next tier down you can realistically reach — or, if already well above, convert up to the top of your current tier rather than wasting headroom.
3. Calculate the conversion headroom. Subtract your projected non-conversion MAGI from the target threshold. The result is the maximum Roth conversion amount that keeps you below the bracket. Build in a $500 to $1,000 buffer for unexpected income (a surprise capital gains distribution from a mutual fund, for example).
4. Execute in Q4 when possible. By October or November, you have visibility into nearly all income for the year. A Q4 conversion reduces the risk of overshooting because most income uncertainty has resolved. If you convert in January and receive unexpected income later, you cannot “undo” the conversion — recharacterization of Roth conversions was eliminated by the Tax Cuts and Jobs Act of 2017.

Worked example: David, age 67, $680,000 traditional IRA

David is a single filer who retired at 65. He has a $680,000 traditional IRA (rolled over from a 401(k)), $120,000 in a Roth IRA, and $95,000 in a taxable brokerage account. His annual income sources:

• Social Security at 67 (FRA): $28,800/year ($24,480 taxable at 85% inclusion)
• Small pension from a prior employer: $14,400/year
• Taxable brokerage dividends and capital gains: $6,200/year
• Municipal bond interest (inside brokerage): $2,100/year

David’s non-conversion IRMAA MAGI: $24,480 + $14,400 + $6,200 + $2,100 = $47,180. His headroom below $103,000 is $55,820. With a $1,000 buffer for unexpected income, David can safely convert $54,800 from his traditional IRA to his Roth IRA each year without triggering IRMAA.

At this pace, David converts approximately $54,800/year. Over six years (ages 67 to 72, before RMDs begin at 73 under SECURE 2.0), he converts roughly $329,000 — reducing his traditional IRA balance from $680,000 to approximately $351,000 (plus or minus investment returns). His first-year RMD at age 73 on a $351,000 balance is approximately $13,245 (using the Uniform Lifetime Table divisor of 26.5), compared to $25,660 on the original $680,000 — a difference of $12,415 in annual taxable income that no longer pushes him toward IRMAA thresholds.

What happens if David ignores the IRMAA bracket

If David converts $80,000/year instead of $54,800, his MAGI reaches $127,180 — above the $103,000 threshold but below the $129,000 Tier 2 bracket. He pays an additional ~$1,052/year in Medicare surcharges. Over 6 years, that is approximately $6,312 in extra premiums. The larger conversions reduce his traditional IRA faster (to roughly $200,000 by age 73), saving approximately $5,700/year in future RMD-generated income. Whether the upfront IRMAA cost is worth the future RMD reduction depends on David’s life expectancy, tax rates, and the investment return differential between traditional and Roth accounts. For most retirees, the math favors staying below the bracket unless the traditional IRA balance is large enough that aggressive conversion produces multi-decade compounding benefits that dwarf the surcharge.

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

If a one-time income event pushed your MAGI above an IRMAA threshold — a severance payment, a property sale, a large capital gain from a concentrated stock position — you may be able to appeal the surcharge if a qualifying life-changing event also occurred. The eight qualifying events recognized by SSA are: marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property, loss of pension income, and employer settlement payment.

The critical limitation: a one-time Roth conversion or voluntary asset sale does not qualify as a life-changing event on its own. However, if you retired in the same year (work stoppage), you can file Form SSA-44 requesting that SSA use your reduced post-retirement income to determine IRMAA instead of the higher MAGI from the year you were still working. You must provide documentation of both the qualifying event and your revised income estimate.

There is no formal filing deadline for Form SSA-44, but you should file as soon as you receive your Initial IRMAA Determination notice (typically mailed by SSA in late fall for the following year’s premiums). If the appeal is approved, the surcharge is removed or reduced retroactively, and any overpaid premiums are refunded. If denied, you can request a formal hearing before an administrative law judge.

Withdrawal sequencing to stay below the cliff

IRMAA bracket management is not just a Roth conversion exercise — it governs your entire withdrawal sequence. The order in which you draw from traditional, Roth, and taxable accounts determines your MAGI in each year, which determines your IRMAA tier two years later.

Before RMDs begin (typically ages 62 to 72): Spend from taxable accounts and/or Roth accounts for living expenses. This keeps your MAGI low, maximizing Roth conversion headroom. Every dollar of traditional IRA you convert now is a dollar that will not generate a taxable RMD later. If your taxable account is insufficient for living expenses, withdraw from the traditional IRA only what you need, then convert additional headroom to Roth.

After RMDs begin (age 73+): Take the RMD from your traditional IRA first (it is mandatory and taxable regardless of whether you need the income). If the RMD exceeds your spending needs, invest the excess in a taxable brokerage account. Supplement any remaining spending needs from Roth (tax-free, no MAGI impact). If you are charitably inclined, use qualified charitable distributions (QCDs) to satisfy part or all of your RMD without increasing AGI — directly reducing your IRMAA MAGI.

Municipal bonds and IRMAA: Many retirees hold municipal bond funds for tax-free income, not realizing that the interest counts toward IRMAA MAGI even though it is excluded from federal income tax. If you are within $10,000 of an IRMAA threshold, evaluate whether the tax-exempt yield on your muni holdings justifies the IRMAA exposure. In some cases, replacing munis with tax-efficient equity index funds (which generate mostly unrealized gains) produces a lower IRMAA MAGI while maintaining or improving after-tax returns.

Key takeaways

• The first IRMAA tier begins at $103,000 MAGI for single filers ($206,000 MFJ) based on 2024 income, and it operates as a cliff: one dollar over the threshold triggers the full Tier 1 surcharge of approximately $888/year in Part B premiums plus roughly $164/year in Part D surcharges per person. For a married couple both on Medicare, the household cost doubles to approximately $2,100 to $2,200/year. There is no proration and no phase-in — you either pay the standard premium or you pay the surcharge for the entire year.
• Roth conversion sizing should be anchored to the IRMAA bracket, not just the income tax bracket. Calculate your non-conversion MAGI for the year, subtract it from $103,000 (or $206,000 MFJ), and convert up to that amount minus a small buffer. Executing conversions in Q4 — when most income for the year is known — reduces the risk of accidentally overshooting. Recharacterization of Roth conversions is no longer available, so an overshoot cannot be reversed.
• Systematic annual conversions during the pre-RMD window (typically ages 62 to 72) compound the benefit: each year’s conversion reduces the traditional IRA balance, which reduces future RMDs, which reduces future MAGI, which reduces future IRMAA exposure. A retiree converting $54,800/year for six years can cut their eventual RMD by roughly half — permanently lowering their IRMAA MAGI in every subsequent year.
• If a one-time income event combined with a qualifying life-changing event (retirement, death of spouse, divorce) pushed you over an IRMAA threshold, file Form SSA-44 with the Social Security Administration as soon as you receive your IRMAA determination notice. A successful appeal removes the surcharge retroactively. A Roth conversion or voluntary asset sale alone does not qualify — but if you also retired, reduced work hours, or experienced another qualifying event in the same period, the appeal mechanism applies.
• Withdrawal sequencing matters as much as conversion sizing. Before RMDs begin, spend from taxable and Roth accounts to keep MAGI low and maximize conversion headroom. After RMDs begin, use qualified charitable distributions to satisfy required distributions without increasing AGI. Re-evaluate municipal bond holdings if tax-exempt interest is pushing your IRMAA MAGI above a threshold — the IRMAA surcharge can exceed the tax benefit of muni income.