Do Roth conversions affect Medicare IRMAA?

Short answer: Yes. To the extent a Roth conversion creates taxable income, it can increase the modified adjusted gross income used to determine a future Medicare income-related monthly adjustment amount, commonly called IRMAA.

That does not automatically make the conversion a mistake. It means the Medicare effect belongs in the same projection as the current tax cost, future required distributions, survivor taxes, investment horizon, estate objectives, and the source of cash used to pay the conversion tax.

Why the timing can feel disconnected

A Roth conversion occurs in one calendar year. Medicare’s income-related adjustment usually appears later because the Social Security Administration generally requests tax-return information from the IRS for the year two years before the premium year. A conversion completed this year may therefore influence Medicare premiums in a later year rather than immediately.

IRMAA can affect both Medicare Part B and Part D. It is assessed in tiers, which means a relatively small amount of additional income can sometimes move a household into a higher tier. Thresholds and premium amounts are updated over time, so planning should use the figures applicable to the conversion year and the projected premium year rather than a table copied from an older article.

What part of a conversion matters?

The IRS explains that converting untaxed traditional IRA amounts to a Roth IRA results in taxation of those amounts. IRMAA calculations use a Medicare-specific version of modified adjusted gross income: adjusted gross income plus certain tax-exempt interest. The planning question is therefore not simply, “How large is the conversion?” It is, “Where does total projected MAGI land after the conversion and every other income item is included?”

Other events can occupy the same income space: wages, pensions, taxable Social Security benefits, interest, dividends, realized capital gains, business income, required distributions, and a property or business sale. A conversion that looks comfortable in isolation may cross another threshold after those items are added.

IRMAA is one cost—not the complete answer

A disciplined review compares alternatives. Paying additional tax and possibly IRMAA now may still be reasonable if it meaningfully reduces later required distributions, creates more tax-diversified retirement income, improves the surviving spouse’s flexibility, or supports legacy goals. Conversely, a conversion may be unattractive when the current combined cost is high and the projected future benefit is limited.

The right comparison is cumulative and multi-year. It should measure the conversion tax, potential Medicare premium changes, future account balances, projected distributions, and the taxes that might otherwise be paid later. One year’s premium should not be ignored—but it should not be evaluated without the rest of the plan.

Can IRMAA be reduced after income falls?

SSA permits a request for a new determination when a qualifying life-changing event causes household income to fall. Examples include marriage, divorce, death of a spouse, work stoppage, work reduction, and certain losses of income. The agency provides Form SSA-44 for this process.

A voluntary Roth conversion is not itself one of the listed life-changing events. Someone who later experiences a qualifying event should review the current SSA requirements and evidence rules rather than assuming a conversion-related IRMAA adjustment will automatically be reversed.

A useful decision sequence

1. Project income without a conversion.
2. Add the proposed conversion and identify the marginal federal and state tax effects.
3. Estimate whether projected MAGI enters a different IRMAA tier.
4. Compare several smaller conversion amounts instead of only an all-or-nothing choice.
5. Model later RMDs, survivor filing status, and the expected use of Roth assets.
6. Coordinate the final assumptions with the client’s qualified tax professional before implementation.

For the broader conversion framework, see How much should you convert to Roth each year? and our Medicare and IRMAA planning page.