Medicare prices each year off the tax return you filed two years earlier, and the income-related surcharge is a cliff rather than a slope. A dollar over a threshold buys the whole step, for twelve months — and the bill arrives long after the money moved.
On $70,000 of other income, converting $39,000 costs nothing. Converting $40,000 costs $1,148 a year in Medicare premiums. The $1,000 that crossed the line was the most expensive money in the plan.
A single filer with $70,000 of other income, aged 63. The surcharge shown is what one beneficiary pays for the year Medicare prices off this return.
| Converted | MAGI | Surcharge / year | Added |
|---|---|---|---|
| $0 | $70,000 | $0 | — |
| $25,000 | $95,000 | $0 | — |
| $39,000 | $109,000 | $0 | — |
| $40,000 | $110,000 | $1,148 | +$1,148 |
| $67,000 | $137,000 | $1,148 | — |
| $68,000 | $138,000 | $2,885 | +$1,736 |
| $100,000 | $170,000 | $2,885 | — |
| $135,000 | $205,000 | $4,620 | +$1,735 |
Plan year 2026. Per beneficiary, per year.
| MAGI over $109,000 | +$1,148 |
| MAGI over $137,000 | +$1,736 |
| MAGI over $171,000 | +$1,735 |
| MAGI over $205,000 | +$1,735 |
| MAGI over $500,000 | +$581 |
| MAGI over $218,000 | +$1,148 |
| MAGI over $274,000 | +$1,736 |
| MAGI over $342,000 | +$1,735 |
| MAGI over $410,000 | +$1,735 |
| MAGI over $750,000 | +$581 |
A conversion window is usually several years long, and the surcharge lands on whichever of them crossed a line. The planner runs the whole window and shows which year the bill comes from — alongside what the conversion did to the rest of the return.
The income-related monthly adjustment amount (IRMAA) added to Medicare Part B and Part D premiums, priced off modified adjusted gross income from two years earlier. Figures are the annual surcharge for one beneficiary.
Medicare prices each year off the return filed two years before, so a conversion at 63 sets the premium at 65.
A married couple where both are enrolled pays the surcharge each, so double these figures. Thresholds are indexed annually, and a one-off event can be appealed with form SSA-44 only for a listed life-changing event — a Roth conversion is not one of them.
Computed by the same engine the planner runs, and asserted against it by a test.
This is a projection under stated assumptions — not financial or tax advice.