The 2026 IRMAA Cliff Map

IRMAA — the Income-Related Monthly Adjustment Amount — is an extra charge added to your Medicare Part B and Part D premiums once your modified adjusted gross income (MAGI) rises above a threshold. It is structured as a staircase of cliffs: one dollar of MAGI over a boundary moves your entire year's premium up to the next step. This study maps those 2026 cliffs directly — where they sit, what the marginal dollar costs at each one, and the headroom from a grid of income positions to the next boundary. It does not model a Roth conversion or a break-even rate; that is the companion conversion-cost study, cross-linked below.

What IRMAA is (and the two-year lookback)

Everyone on Medicare pays a base Part B premium. Above the first MAGI threshold, IRMAA adds a per-tier surcharge on top of both Part B and Part D. Three features make the surcharge easy to trip over:

• It is a cliff, not a phase-in. Each tier applies to the whole year the moment MAGI clears the boundary. There is no gradual ramp — a dollar over and a thousand over cost exactly the same.
• It runs on a two-year lookback. Your 2026 premiums are set from the MAGI on the tax return you filed two years earlier. Income you realize this year shows up as a surcharge two years later, and if your income drops back below the boundary, the surcharge falls away again.
• It is charged per person. The surcharge applies to each enrollee. A married couple who are both on Medicare each pay it, so their annual cost at any tier is exactly twice the per-person figure.

The boundaries below use the official convention: an interior tier applies only when MAGI is greater than its floor, so income landing exactly on a round threshold stays in the lower tier. The one exception is the top tier, whose floor is inclusive (MAGI at or above $500,000 single / $750,000 MFJ already pays the top surcharge).

The 2026 cliff map

Every boundary, for both filing statuses. "Surcharge below" is the annual Part B + Part D surcharge (per person) for MAGI just under the boundary; "surcharge at/above" is the surcharge once you cross it. The cliff cost is the difference — the price of the single dollar that crosses. The last column expresses that cliff cost as a percentage of that one dollar: a deliberately extreme "effective marginal rate on the crossing dollar," shown to make the point that a cliff punishes the marginal dollar, not the average one. Click any column to sort.

*A one-dollar illustration: the per-person cliff cost divided by the single dollar of MAGI that triggers it, as a percentage. It is not a tax bracket rate and does not apply to any dollar other than the one that crosses the boundary.

Why one dollar is so expensive at a cliff

A normal marginal tax works on a ramp: an extra dollar of income is taxed at your bracket rate, so a dollar costs cents. A cliff works differently. The surcharge is a flat annual dollar amount attached to a tier, and the whole amount switches on at the boundary. So the dollar that crosses the boundary carries the entire step — $1,148.40 at the first cliff, up to $1,736.40 at the steepest one — while every dollar before it and after it inside the tier carries nothing extra. That is why the "effective marginal rate on the crossing dollar" column reaches into the tens of thousands of percent: it is one dollar doing the work of the entire step. The practical consequence is that the expensive mistake is not converting or realizing a lot of income — it is realizing just a little too much and clipping a new tier for no real benefit.

Couples pay it twice

Because IRMAA is charged per enrollee, a married couple who are both on Medicare face double the per-person cliff. The steepest boundary that costs one person $1,736.40 costs a two-Medicare couple $3,472.80 for the year. The married-filing-jointly boundaries sit at roughly twice the single-filer thresholds, but the surcharge per person at each tier is identical to a single filer's — the couple simply pays it two times over. The "couple" column in the map above shows that doubled figure for the MFJ rows.

How much headroom to the next cliff?

The flip side of a cliff is the flat ground before it: every dollar of MAGI up to the next boundary adds no surcharge at all. This grid walks a range of MAGI positions and shows the current tier, the annual per-person surcharge you are already paying at that income, and the room left before the next cliff. Filter by filing status and sort any column.

CC-BY-4.0 — free for any use including republication and journalism, with attribution to QuantCalc Research.

Related

Assumptions

• Figures are the 2026 Medicare Part B + Part D IRMAA surcharge tiers, per enrollee, annualized (monthly add-on × 12).
• Each cliff row prices the single dollar that crosses the boundary, using the official boundary rule: interior tiers apply for MAGI strictly above the floor; the top tier applies at or above its floor.
• The per-couple column assumes a married-filing-jointly household in which both spouses are enrolled in Part B and Part D; it is twice the per-person surcharge.
• The "rate on the crossing $1" is an illustration of the cliff cost relative to one dollar of MAGI, not a marginal tax bracket rate and not a figure that applies to any other dollar.
• MAGI is the modified adjusted gross income from the tax return two years prior (the CMS lookback year). The 2026 thresholds are inflation-indexed and drift over time.
• Married filing separately (lived with spouse) uses a different compressed schedule and is out of scope here.

Methodology

Changelog

• v2026.1 — initial release. 10 cliffs (5 tiers × 2 filing statuses) plus a 113-row headroom grid, generated from irmaa.js / constants-2026.js.

Dataset license: CC-BY-4.0. QuantCalc is an independent retirement-planning research project. Not affiliated with, endorsed by, or sponsored by any state or federal agency, including CMS or the Social Security Administration. Not financial, tax, or legal advice.