Roth conversions and IRMAA: the two-year echo

A Roth conversion is taxed in the year you convert — and then, two years later, it echoes: Social Security prices that year's Medicare premiums off the return with the conversion income in it. A $120,000 conversion in 2024 can mean top-tier IRMAA surcharges through 2026 — thousands in extra premiums for a move that was still, on balance, smart. Here's how the pieces fit.

The mechanics

• Conversion income counts in MAGI (AGI + tax-exempt interest) for the conversion year.
• Premiums two years later use that MAGI. Convert in 2026 → the echo lands in 2028 premiums.
• The brackets are cliffs: $1 over a line raises the surcharge for the whole year, per person — a converting couple pays it twice.

Can you appeal the conversion year's IRMAA?

Not on the conversion alone — it isn't a listed life-changing event. But conversions are often timed with retirement, which is. The classic case: convert heavily in your last working year, retire, and two years later face a surcharge priced off the combined salary-plus-conversion income. If your post-retirement income has genuinely dropped a tier, the work-stoppage event is your SSA-44 door — the conversion is context, the retirement is the case. Run your numbers in the checker.

Planning the next conversion

• Size to the bracket, not the tax bracket alone. The IRMAA cliff nearest your target MAGI is a real cost line — sometimes converting slightly less this year beats converting more.
• Watch both spouses' exposure: joint MAGI sets both premiums.
• Married filing separately is a trap for converters: its IRMAA table jumps to near-top rates almost immediately.
• Coordinate the calendar: conversion timing, capital gains, and RMDs all land in the same MAGI. One year of stacking can cost two years of premiums.

This page is educational, not tax or financial advice — conversion decisions deserve a professional who can see your whole return.