The short answer
A Roth conversion raises IRMAA exposure because converted amounts count in gross income for the conversion year, per IRS Publication 590-A, and Social Security generally prices each premium year from the return two years back. One conversion echoes into one premium year, bounded by the published surcharges.
Say you convert in 2026. Nothing happens to your Medicare premium that year, or the next. It appears in 2028, long after the decision, on a bill that never mentions the conversion.
How does a Roth conversion affect IRMAA?
A Roth conversion affects IRMAA because converted amounts are gross income for the conversion year, under IRS Publication 590-A, and IRMAA reads income. Call it the Third Line Item: a conversion's true cost sheet is the tax paid, the tax saved, and possibly one year of higher premiums.
The Third Line Item joins two published rules. The IRS: conversion amounts are included in gross income, normally on the return for the year converted. Social Security: each premium year is priced from the most recent return the IRS provides, generally two years back. Both rules are the government's. The naming is ours.
Whether the third line changes any decision is not this page's call, and the page will say so again below. Its job is making the line visible and computable.
When does the surcharge actually hit?
The surcharge from a conversion hits generally two years after the conversion year, because Social Security prices each premium year from the most recent return the IRS provides: convert in 2024 and the income appears on the 2024 return, which generally sets 2026 premiums.
That year-chain is the stated cycle's own arithmetic, and it runs on any start year: the conversion's income lands on its year's return, the return is filed the following year, and it generally prices the premium year after that.
The echo is also single: each premium year is re-determined from the then-most-recent return, so one conversion year raises one premium year and then leaves the record when the next return replaces it.
How do I model the two year lag?
Modeling the lag means placing each conversion year's MAGI against a bracket map that will only be published two years later. The knowable parts are the conversion amount, the rest of the year's income, and the current map; the unknowable part is the future map itself.
MAGI, in Social Security's definition, is total adjusted gross income plus tax-exempt interest income, so the conversion sits on top of everything else the year produces.
The current reference points carry their year: in 2026 the surcharges begin above 109,000 dollars of MAGI for individual filers and 218,000 dollars for joint filers. Future bounds are published year by year, and this publication does not project them, which is the honest limit of any model.
Is the conversion still worth it?
Whether a conversion is worth it is not a question this page can answer, because the worth lives in your tax rates, your horizon, and your heirs, none of which Medicare publishes. What the published record contributes is one clean fact: the premium effect is bounded and computable.
Bounded, because the surcharge ladder has a published top: the additions per bracket are fixed amounts, and the companion cliff article prices each step of the current year's ladder. Computable, because the echo's timing and duration follow the stated cycle.
So the honest framing is neither alarm nor dismissal: the Third Line Item is a real, finite number that belongs on the sheet you and your tax professional read together.
Can I size a conversion around the brackets?
Sizing a conversion around the brackets is arithmetic the sources permit: conversion income lands in a chosen year, MAGI is that year's adjusted gross income plus tax-exempt interest, and the bracket rows are published bounds. Filling a row without crossing it is a computable target against the current map.
Four things are knowable when you do that arithmetic, and one is not.
- The conversion amount lands in gross income for the year you convert it
- MAGI is that year's adjusted gross income plus tax-exempt interest income
- The bracket bounds are published, so this year's map is a real target
- A bound has a hard edge, so one dollar over prices the entire next step
What is not knowable is the map that will actually price the conversion. The premium is set two years later, against bounds published for that year and not for this one.
Whether to aim at any of this is the decision the disclaimer at the bottom of this page means: the mechanics are public arithmetic, and the choice is yours with your tax professional.
What ages matter most for planning?
The ages that matter are set by two clocks: Medicare eligibility at 65 and the two year lookback, which together make 63 the first year whose income can echo into a Medicare premium. From 63 on, every year's MAGI is potentially a premium input.
That 63 is derived, not decreed: Medicare is federal health insurance for anyone 65 and older, Social Security generally reads the return from two years back, and the subtraction is ours.
One more published age belongs on the planning calendar: 70 and a half, the earliest age for a qualified charitable distribution, the IRS mechanism the companion planning article covers. Ages this ledger's sources do not state, this page does not state.
How the charge reaches you is worth knowing before you plan around it, because it does not arrive the way people expect.
Social Security sends a letter stating the premium amounts and the reason for them. If you have both Part B and drug coverage, both get the adjustment; if you have only one, only that one does.
Payment differs too. For people billed rather than having it deducted, Part B including its adjustment is billed every 3 months, and the Part D adjustment every month.
Three ages set the planning calendar, and each one is published.
| The age | What it opens | Where it comes from |
|---|---|---|
| 63 | The first year whose income can price 65 | Subtraction, not statute |
| 65 | Medicare eligibility | Federal health insurance from age 65 |
| 70 and a half | The qualified charitable distribution | The earliest age the IRS allows one |
The first row is the one people miss, because nothing happens at 63 that you can feel.
What this means for you
A Roth conversion is a tax decision with a Medicare echo: income now, premium effect two years on, one year per conversion, bounded by published surcharges. The mechanics are all published and computable; the verdict belongs to you and your tax professional, with the echo priced in rather than discovered.
For the ladder the echo lands on, read the brackets article. For the hard edges, the cliff article. For the tools that move MAGI in other directions, the planning article beside this one.
FAQ
Does a Roth conversion count as income for IRMAA?
Yes, by the IRS's own rule. Publication 590-A states that amounts converted from a traditional IRA to a Roth IRA must be included in gross income, normally on the return for the year of the conversion. IRMAA then reads that return through Social Security's definition of MAGI, total adjusted gross income plus tax-exempt interest income.
The two rules connect with no gap: the conversion raises gross income, gross income raises MAGI, and MAGI meets the bracket table. None of this makes a conversion wrong; it makes the conversion's premium effect a fact to compute rather than a surprise to receive, which is this article's entire purpose.
When would a conversion made in 2026 show up in my premiums?
Generally in 2028, by the cycle's own arithmetic. The income lands on the 2026 return, filed in 2027, and Social Security generally prices each premium year from the most recent return the IRS provides, two years back, the same pattern its page states for 2026 premiums reading tax year 2024.
The word generally matters: occasionally the IRS supplies an older return, and that case has its own correction path through Social Security. The bracket map the 2026 conversion will actually meet is the 2028 map, unpublished today, which is the modeling limit this article names rather than papers over.
The delay is structural rather than administrative. Social Security uses the most recent federal tax return the IRS provides (G13), which is why a conversion lands on a premium two years later rather than the next month.
Does the surcharge repeat every year after one conversion?
No. Each premium year is re-determined from the then-most-recent return, so a single conversion year produces a single elevated MAGI, one elevated premium year, and then the record moves on when the next return replaces it.
The echo repeats what one return said, once. A series of conversion years is different arithmetic: each year's conversion writes its own future premium year, one for one.
That one-for-one structure is exactly what makes the premium effect computable in advance, and it is also why a conversion plan spread across years meets several smaller echoes rather than one large one.
It does not repeat, because the income does not. A conversion is gross income for the conversion year only (G15), so it affects the premium year tied to that return and no other.
Is one big conversion better than several small ones?
The published record prices the structures differently but does not rank them. One large conversion concentrates MAGI into a single year: one loud echo, priced by whichever rows it crosses, edges included. Several smaller conversions spread MAGI across years: several quieter echoes, each meeting its own future bracket map.
The cliff arithmetic in the companion article is what makes the difference computable, and the tax side of the ledger, rates now versus rates later, is not Medicare's subject at all. Which structure fits your situation is precisely the decision this publication leaves with you and your tax professional.
This page cannot answer it and will not pretend to. What it can give you is the mechanism: the conversion is income in the year it is made (G15), and the thresholds it may cross are the ones published for that year (G4).
What official sources govern all of this?
Three, and all are quotable. IRS Publication 590-A carries the conversion income rule: converted amounts are included in gross income for the conversion year. Social Security's higher-income premiums page carries the rest: the MAGI definition, the two year cycle with its named tax years, the bracket tables, and the letter that announces a determination.
And CMS's yearly fact sheet publishes the surcharge amounts alongside the premiums. Anything not in those sources, future bracket bounds included, is projection, and this page deliberately contains none. The letter in your mailbox and the current year's charts are the whole verifiable record.
The Medicare side rests on the thresholds and the lookback rule (G4, G13). The tax side rests on IRS Publication 590-A for the conversion being gross income in its year (G15).
