The IRMAA Cliff

The surprise bill

A couple does what their financial advisor tells them: in 2024, they convert $80,000 from a Traditional IRA to a Roth. Their tax bill that April looks reasonable. Two years later, January 2026, they receive a letter from Social Security: their Medicare Part B premium is going up by $5,800/year — combined, $11,600/year for the couple. Plus an additional Part D surcharge of about $1,650/year combined. Total cost of that conversion they did two years ago: roughly $13,250/year, for one full year, on top of the federal tax they already paid.

Welcome to IRMAA — the Income-Related Monthly Adjustment Amount. The most-overlooked tax cliff in retirement planning, by a wide margin.

What IRMAA actually is

Medicare Part B (doctors, outpatient) and Part D (prescription drugs) charge a base premium that the government partially subsidizes. The standard 2025 Part B premium is about $185/month per person — the government picks up the other ~75% of the actual cost.

For higher-income retirees, the government claws back some of that subsidy by adding a surcharge to your monthly premium. That surcharge is IRMAA. It's calculated annually based on your modified adjusted gross income (MAGI) from two tax years prior.

2025 thresholds for MFJ (single thresholds are roughly half):

Tier 0:  MAGI ≤ $212,000        → no IRMAA (standard premium)
Tier 1:  $212,000 – $266,000    → +$1,052 / person / year
Tier 2:  $266,000 – $334,000    → +$2,644 / person / year
Tier 3:  $334,000 – $400,000    → +$4,236 / person / year
Tier 4:  $400,000 – $750,000    → +$5,827 / person / year
Tier 5:  > $750,000              → +$6,357 / person / year

(Numbers cover Part B + Part D surcharges combined.
 Single thresholds are half of MFJ for Tiers 0–3
 — $106k / $133k / $167k / $200k — then $500k for Tier 4.
 Tier 4 caps are statutorily fixed and never index.)
      

Thresholds inflate slowly (about 2.5%/year recently). Surcharges grow with healthcare inflation.

Why this is "a cliff" — not a slope

IRS income tax is a graduated system. Earn one dollar over the 22% bracket and that one dollar gets taxed at 24%, not the rest of your income. The damage from crossing a bracket is gradual and proportional.

IRMAA isn't like that. The tiers are hard cliffs. One dollar over the threshold and your entire premium jumps to the higher tier. For a married couple:

• MAGI of $265,999 → no Tier 2 surcharge ($0 IRMAA for that tier)
• MAGI of $266,001 → Tier 2 fires → $2,644 × 2 = $5,288/year

That $2 of extra income just cost you $5,288. The implied marginal "tax rate" on that $2 is effectively 264,400%. Cliffs do not get more vertical than this.

Worse: IRMAA is a one-year-at-a-time calculation. So if you trip a tier in one year only (say, by doing a one-time large Roth conversion), the surcharge fires for one year only. But if your income stays elevated, the surcharge stays elevated — and it compounds across both spouses.

The two-year lookback (the part that bites)

Here's the twist that catches almost everyone: IRMAA in 2026 is based on your 2024 tax return. The damage from a 2024 Roth conversion shows up in your 2026 Medicare premium, two full years later. By the time the bill lands, you've usually forgotten what you did and it feels arbitrary.

Practical implications:

• You can't react to it. When the SSA letter arrives in late 2025 telling you what your 2026 premium will be, the underlying income event happened in 2024 — there's nothing you can do about it now.
• You have to plan in advance. A Roth conversion done today doesn't show up on your Medicare bill until two years from now. So if you're nearing the IRMAA threshold this year, the cost won't be visible until far enough in the future that most retirees forget about it.
• One bad year ripples forward. An unexpectedly large RMD, an inherited IRA distribution, a large capital gain from selling a house — any one of these can spike a single year of MAGI and trigger IRMAA two years out.

The Roth conversion interaction

Standard Roth conversion advice says: "convert up to the top of the 22% bracket" or "convert up to the top of the 24% bracket" to fill cheap brackets while you can. Both of those bracket tops sit well above the IRMAA Tier 1 threshold ($212k MFJ in 2025).

Concretely, here's what filling the 22% bracket looks like for a typical retiree couple already collecting $40k/year of Social Security and a $25k pension:

Standard ordinary income:    $65,000 (SS taxable + pension)
22% bracket top (2025 MFJ):  $206,700 (taxable income)
Standard deduction:          $30,000
AGI ceiling = bracket_top + std_ded ≈ $236,700

But IRMAA Tier 1 threshold:  $212,000 AGI

So "fill the 22% bracket" pushes AGI to ~$237k — Tier 1!

The IRMAA cost: $1,052 × 2 = $2,104/year — for the year that conversion shows up on your Medicare bill. For a single year, the math may still work in favor of the conversion (you saved 22% federal on the conversion, much more than the $2k in IRMAA). But if you do the same conversion every year for 10 years, you're paying $2,104/year × 10 = $21,040 in cumulative IRMAA on top.

And if you push just over Tier 2 ($266k AGI), the per-year IRMAA jumps to $5,288/year per couple. Over 10 years that's $52,880. The math gets uncomfortable fast.

The "stay just below" strategy

The most-effective IRMAA-aware tactic: deliberately size your Roth conversions to land just below an IRMAA threshold rather than filling a full ordinary-income tax bracket. Concretely:

• A retiree with $65k of fixed income could convert about $146k to land at $211,999 MAGI — staying in Tier 0.
• That's only modestly less conversion than filling the 22% bracket fully (which would have been ~$170k), but it saves $2,104/year of IRMAA two years later.
• Compounded over a multi-year conversion plan, the "stay just below" version typically outperforms "fill the bracket" by $10,000–$50,000 in cumulative lifetime cost.

The trick is that the "ideal" conversion amount depends on:

• Your other income (pension, RMDs in later years, SS)
• Whether your spouse's SS hasn't started yet (low-income window)
• Whether you have ACA subsidies (a separate cliff, see below)
• Where the IRMAA thresholds are in the future year you'll actually be on Medicare

This is exactly why a calculator beats spreadsheets — too many moving parts to track by hand.

Appealing IRMAA: the SSA-44 form

IRMAA isn't always permanent. If your income drops because of a "life-changing event," you can appeal and have the surcharge reduced or eliminated — using Form SSA-44.

Qualifying life-changing events under the SSA rules:

• Marriage
• Divorce or annulment
• Death of a spouse
• You or your spouse stopped working (full retirement counts)
• You or your spouse reduced your work hours significantly
• Loss of income-producing property (involuntary, not a planned sale)
• Loss of pension income (employer plan terminated, not just stopped contributing)
• Receipt of settlement payment from a former employer

Notable absence: "I did a one-time Roth conversion" is NOT a qualifying event. Voluntary tax-planning maneuvers don't qualify for relief. Neither does "I had a large RMD" (RMDs are predictable). The form is for involuntary income changes that won't recur.

If you retire mid-year and your IRMAA surcharge is based on the high-income working year two years prior, that is a qualifying event ("stopped working"). The SSA-44 will adjust your premium based on your current reduced income instead. This is the most common successful appeal.

The interaction with other tax cliffs

IRMAA is the largest income-based cliff retirees face, but it's not the only one. Roth conversion sizing has to dodge several cliffs simultaneously:

• Social Security taxability phase-in — at provisional income above $32k MFJ, SS becomes 50% taxable; above $44k, 85%. Roth conversions push provisional income up. Covered in detail in our previous post on the SS tax torpedo.
• ACA Premium Tax Credit cliff (under non-enhanced rules) — for pre-Medicare retirees, exceeding 400% of FPL eliminates all PTC subsidies. Can cost $10,000+/year if you cross it.
• Net Investment Income Tax (NIIT) — 3.8% surtax on investment income above $250k MFJ AGI. Frozen-threshold, so it bites more retirees every year.
• 0% LTCG bracket — capital gains are literally free if your taxable income is under ~$96,700 MFJ. Roth conversions stack right on top of this threshold.
• IRMAA itself — the topic of this post, with 5 hard tiers each costing $1,052+/person/year.

All of these cliffs interact. A conversion that respects one might trigger another. The optimal conversion sizing is the one that respects all of them simultaneously — which is computationally annoying for humans but trivial for a tool.

How RothHelper handles it

The RothHelper calculator models all five IRMAA tiers with the real two-year MAGI lookback (using your pre-projection household income as a proxy for the first two retirement years). The Projections table shows per-year IRMAA tier and dollar surcharge for each strategy, so you can see at a glance which strategies stay below thresholds and which cross them.

The Advisor tab's lifetime tax cost ranking includes IRMAA surcharges — so the recommended strategy is one that respects the tiers, not just the federal bracket math. The Sensitivity tab can show you exactly how much IRMAA costs your final net worth, often surprising users with how large the impact is.

What the tool doesn't do: hold the conversion amount precisely under the next tier threshold automatically. The "optimize" strategy finds the conversion amount that minimizes lifetime tax cost (including IRMAA), but it can recommend amounts that just barely cross a tier when the cumulative federal tax savings exceed the IRMAA cost. If you want to stay strictly under, the "Custom amount" strategy lets you specify your own threshold-aware target.

What to do

Concrete steps for any retiree near retirement who's considering Roth conversions:

1. Run the projection. See which strategy your situation actually favors. Don't assume "fill the 22% bracket" works for you just because it's what everyone says.
2. Look at the IRMAA tier column for each strategy, year by year. Compare lifetime IRMAA cost between strategies.
3. Try the "Optimize" strategy. It accounts for IRMAA in its lifetime-tax-minimization search.
4. Try a manual approach. Use the "Custom amount" strategy with a number that lands you $1,000–$5,000 below the next IRMAA threshold each year (giving yourself buffer for unexpected income).
5. Watch the two-year lookback. Income today affects Medicare two years from now. The year before you go on Medicare (typically age 64) is the last year your income matters for IRMAA — anything in that year shows up on the bill you'll receive starting age 66.
6. File SSA-44 if you have a legitimate life-changing event. Recent retirees especially should file it — it's the most successful IRMAA appeal.