2026 IRMAA Brackets: How Roth Conversions Can Trigger Medicare Premium Cliffs

Medicare premiums are not the same for everyone. If your income exceeds certain thresholds, you pay significantly more — and the jump is not gradual. It is a cliff. One dollar over the line triggers the full surcharge for the next tier. In 2026, crossing even the first IRMAA cliff can cost a couple on Medicare nearly $2,000 per year in extra Part B premiums alone.

This surcharge is called IRMAA — the Income-Related Monthly Adjustment Amount — and it is one of the expensive surprises retirees often discover too late. The reason it catches people off guard is not the surcharge itself. It is the timing: your 2026 Medicare premiums are based on your 2024 income. A Roth conversion, a large RMD, or a capital gain in 2024 can raise your Medicare costs two years later, in a year that feels completely unrelated.

The mistake is easy to make because tax software shows the income tax cost of a conversion immediately. The Medicare cost shows up later, in a different system, with a different notice — and often after the decision can no longer be changed.

The practical planning question is not just which IRMAA bracket applies. It is how much room you have before the next cliff, and what happens if a Roth conversion, capital gain, or RMD uses up that room. That question should be modeled before you execute — not after.

What IRMAA is — and what it is not

IRMAA is a surcharge added to your standard Medicare Part B and Part D premiums when your Modified Adjusted Gross Income (MAGI) exceeds IRS-defined thresholds. The Social Security Administration calculates it each year from your tax return.

IRMAA is not a tax bracket. It is a switch. Once your MAGI crosses a threshold — even by one dollar — the higher premium turns on for the entire year. The surcharge does not phase in. It does not apply only to income above the line. It applies to your full monthly premium from January through December.

At the standard tier, beneficiaries pay roughly 25% of Medicare Part B costs. At the highest IRMAA tier, that share rises to 85%. The difference is the surcharge.

2026 IRMAA Brackets for Medicare Part B

Your 2026 IRMAA surcharge is determined by your 2024 MAGI. Both Part B and Part D use the same income thresholds.

Single filers (based on 2024 MAGI)

Married filing jointly (based on 2024 MAGI)

The joint thresholds are exactly double the single thresholds for Tiers 1–3. The top brackets diverge: Tier 5 starts at $500,000 for singles and $750,000 for couples.

2026 Part D IRMAA Surcharges

Part D uses the same income thresholds. The surcharge is added on top of your prescription drug plan's own premium.

The married filing separately IRMAA trap

If you file taxes as married filing separately, the threshold structure collapses dramatically. There is no gradual climb through tiers. Above $109,000 in MAGI and below $391,000, you pay the near-top Tier 4 equivalent immediately — skipping Tiers 1, 2, and 3 entirely. Above $391,000, you pay the top tier. This is one of the most expensive and least-discussed features of the IRMAA rules. Run the math on both filing statuses before choosing one.

Why the cliff structure matters more than the tier level

Most articles about IRMAA focus on the tier amounts. The more important number is the distance to the next cliff.

Think about it this way: a single retiree at $136,999 in 2024 MAGI pays the Tier 1 surcharge — $974 extra for the year. A single retiree at $137,001 pays the Tier 2 surcharge — $2,435 extra. The cost of that $2 of additional income is $1,461 in higher Part B premiums in 2026. And that is before Part D IRMAA.

This is where many Roth conversion plans go wrong. They look at the income tax bracket. They ignore the Medicare premium cliff two years later.

A Roth conversion that looks attractive at a 22% marginal rate may look different when the IRMAA surcharge is included. The effective cost is not just income tax — it is income tax plus the increase in Medicare premiums for the full year, for both spouses if both are on Medicare.

The two-year lookback: why 2024 income determines 2026 premiums

The SSA uses income from two years prior because that is when the data is available on your IRS tax return. For 2026 premiums, the relevant year is 2024. For 2027 premiums, it will be 2025.

A Roth conversion executed in 2024 affects Medicare premiums today. An RMD taken in 2024, a home sale, a capital gain distribution from a mutual fund — all of those appear in the 2026 IRMAA calculation. The decision and its Medicare cost land in two different calendar years, which is exactly why the connection is easy to miss.

What counts as income for IRMAA purposes

IRMAA uses MAGI — your Adjusted Gross Income with certain deductions added back. For most retirees, the items that push MAGI higher than expected are:

• •Roth conversions — fully included in MAGI in the year of conversion
• •Required minimum distributions (RMDs) — included as ordinary income
• •Social Security benefits — up to 85% of your benefit may be included
• •Capital gains — both short- and long-term gains from investment sales
• •Rental income — net income from real property
• •Tax-exempt interest — municipal bond interest is added back to MAGI for IRMAA purposes, even though it is excluded from taxable income

One notable exclusion: qualified Roth IRA distributions are not included in MAGI or AGI. This is why Roth conversions done before Medicare enrollment can reduce long-term IRMAA exposure — every dollar moved to Roth now is a dollar that will not appear in future RMDs or MAGI calculations.

A worked example: the conversion that cost $2,297

Here is how the cliff plays out for a married couple, both on Medicare in 2026, who took a Roth conversion in 2024.

Had they limited the 2024 conversion to $7,999 — keeping MAGI at $217,999 — they would have paid zero IRMAA in 2026. The choice to convert $30,000 instead added $2,297 in Medicare premiums on top of the income tax owed on the conversion itself.

The conversion may still have been the right decision. But it should have been a deliberate one, with the full cost — including Medicare — visible in advance.

Before you convert, check the Medicare cost too

RetireSmartIRA models IRMAA cliffs alongside income tax, RMDs, and Social Security

Test Roth conversion amounts on iPhone, iPad, or Mac — see the full cost of each conversion before you execute it. Free through 2026.

Strategies for managing IRMAA exposure

Know your distance to the next cliff before any income decision

The most useful habit is checking how far your MAGI is from the nearest IRMAA threshold before executing a Roth conversion, selling an appreciated asset, or taking an above-minimum RMD. If you are $5,000 below a tier boundary, a $10,000 conversion crosses it. The IRMAA cost may still be worth paying — but you should go in knowing you are paying it.

Front-load conversions in the pre-Medicare years

Because of the two-year lookback, conversions done at ages 63 and 64 affect IRMAA at 65 and 66. Many retirees run larger conversions before Medicare enrollment precisely because IRMAA is not yet a factor. In practice, the Roth conversion window can close faster than people expect once Social Security and RMDs begin layering into MAGI alongside Medicare premium constraints.

Use qualified charitable distributions to reduce RMD income without raising MAGI

If you are 70½ or older and charitably inclined, a qualified charitable distribution (QCD) sends money directly from your IRA to charity. It satisfies your RMD without being included in AGI — and therefore keeps that income out of IRMAA MAGI entirely. In 2026, the QCD limit is $111,000 per person, indexed for inflation. A couple directing $20,000 in RMDs through QCDs keeps that $20,000 out of the IRMAA calculation two years forward.

Appeal if your income has dropped

IRMAA is recalculated every year based on income from two years prior. If the lookback year was unusually high, you are not locked in permanently. File Form SSA-44 with the SSA and provide documentation of a qualifying life-changing event and your current income. The reduction applies going forward, not retroactively, so file promptly.

IRMAA is recalculated every year

No IRMAA tier is permanent. The decisions you make in the current year shape what you pay two years from now. Those numbers exist and are knowable in advance. They just need to be looked at before the decision, not after.