Roth conversion IRMAA

Why a conversion can raise a Medicare premium

A Roth conversion moves money from a traditional retirement account into a Roth account. The converted amount is generally included in income for the year of the conversion. That income raises adjusted gross income and, in most cases, modified adjusted gross income as well.

IRMAA uses modified adjusted gross income from a prior year. The premium for 2026 generally uses income from 2024. A conversion in that lookback year can therefore raise the Part B and Part D amounts for 2026. The Roth account may grow tax-free, but the Medicare premium can arrive before the benefit feels real.

The conversion does not have to be enormous to matter. The question is proximity to a cliff. If the conversion keeps income under the first threshold, the standard premium may still apply. If it crosses the line by one dollar, the surcharge starts for the whole year.

The two-year lookback in practice

The lookback creates a timing problem. In the year you convert, you may be focused on the income tax. The Medicare premium shows up later, based on the same return. A conversion that looks affordable in the tax software can still create an IRMAA surprise.

The practical fix is to plan the conversion with both years in view. Ask what the lookback year income will be after the conversion, not just what the tax bill will be. Then compare that figure with the IRMAA table for the premium year.

If you convert every year, the income may keep you in a higher tier every year. If you convert once, the effect may last for the premium year that uses that return. The pattern matters as much as the amount.

Measure the headroom before you convert

Headroom is the distance from your income to the next bracket line. It is a more useful number than the tier label because it tells you how much room a conversion has before the price changes.

Run the IRMAA cliff checker with the projected income before the conversion. Read the next tier start and subtract the projected income. That is the headroom. Then decide how much to convert, or whether to split the conversion.

Do not treat headroom as a target. It is a boundary. Converting exactly up to the line leaves no margin for a late dividend, a capital gain distribution, or a corrected tax form. A small cushion is usually more comfortable than a perfectly optimized number.

A worked example

A single filer expects $100,000.00 of modified adjusted gross income before any conversion. That is below the first threshold, so the standard tier applies.

The filer converts $20,000.00. Income becomes $120,000.00. That is above the first threshold of $109,001.00, so the first IRMAA tier applies. The Part B total becomes $284.10, and the Part D add-on is $14.50. The combined monthly surcharge is $95.70, or $1,148.40 a year.

The next tier starts at $137,001.00. The filer still has $17,001.00 of headroom before that higher tier. That is the number to watch if the filer considers a second conversion or expects more income later in the year.

Mistakes that create a surprise

The most common mistake is using the income after the conversion for the tax estimate but forgetting the two-year Medicare lag. The tax bill and the premium are related but not simultaneous.

Another mistake is converting in a year with an unusually high income, such as a year with a business sale or a large capital gain. The combined income can cross several IRMAA tiers. The tax cost and the Medicare cost both rise.

A third mistake is assuming that a later market loss undoes the conversion income. The conversion income is reported in the year of the conversion. A market decline after the conversion does not rewrite the return or the IRMAA decision.

What to ask a tax preparer

Ask four questions before converting:

• What will modified adjusted gross income be after the conversion, including all income sources?
• Which IRMAA tier does that figure create in the premium year?
• How much headroom remains before the next tier?
• Would splitting the conversion across two years change the total tax and premium cost?

Bring the IRMAA table to the conversation. A tax preparer can model the tax, but the Medicare table is a separate rule with its own cliff. The best decision usually considers both.

Convert in a low-income year

The IRMAA effect is easier to manage when the conversion year is otherwise quiet. A year with no salary, no business sale, and no large capital gain leaves more room before the first threshold. A retiree who has not started Social Security may have a window with lower income.

That window is not automatic. A pension, an annuity, or a required distribution can fill it. A conversion also raises the income used for other tests, including the Marketplace subsidy rules if the household is not on Medicare yet. The conversion decision belongs in a whole-year plan.

If the window is short, a smaller conversion may be better than a large one that crosses a cliff. The goal is not to convert everything at once. The goal is to use the room you have without paying an avoidable premium penalty.

The Part D side of the same decision

IRMAA has a Part B piece and a Part D piece. The Part B piece changes the medical premium. The Part D piece is added to the drug plan premium, and it can apply even when the Part B amount is already high.

A conversion that moves a household into a higher tier raises both pieces. The monthly difference in the worked example includes both. If one spouse has no Part D plan, that spouse may not pay the Part D amount, but the Part B amount can still apply. The household total depends on who is enrolled.

Do not compare only the Part B line. Read the full tier and the enrollment facts for each spouse.

When a conversion is not worth the premium

A conversion is not worth it if the tax cost, the IRMAA cost, and the loss of other income-based benefits together exceed the long-term benefit. That can happen when the conversion pushes income over a subsidy cliff or a tax bracket at the same time as an IRMAA cliff.

It can also happen when the money will be spent soon. A Roth account is most valuable when it has time to grow and when the owner expects a higher future tax rate. A conversion made only to fill a bracket, without a plan for the money, can create costs without a clear benefit.

Run the numbers with a tax preparer. Use the IRMAA calculator for the premium side. Then decide whether the combined result supports the conversion, a smaller conversion, or no conversion this year.

How much Roth conversion before IRMAA

The usable amount is the headroom to the next IRMAA threshold, not the size of the conversion you would like to make. Start with projected MAGI before the conversion, find the threshold that applies to the filing status, and subtract. The result is the room you have before the next tier.

That calculation answers a narrow question. It does not include the income tax on the conversion, the effect on other credits, or the future tax rate. A conversion that fits under the IRMAA line can still be a poor tax move, and a conversion that crosses the line can still be worthwhile if the tax savings are larger than the Medicare surcharge.

The timing is two years removed. Income in the conversion year generally sets the premium two years later. A conversion in the current year can therefore change a premium after the next tax return is processed. Do not assume the premium will change immediately.

Splitting a conversion can preserve headroom. Converting part of the amount this year and part next year may keep each year below a threshold, but it also spreads the tax and adds two years of planning. The right answer depends on the brackets, the taxpayer's age, and the rest of the income picture.

Use the IRMAA calculator to see the tier and the surcharge, then take the conversion amount to a tax preparer. The calculator does not model the tax on the conversion. It shows the Medicare cost of crossing a line, which is only one part of the decision.

Three honest caveats

1. A Roth conversion can be a sound tax move and still raise IRMAA. The two results are not contradictory.
2. This page does not calculate the income tax on a conversion or promise a tax benefit. It only explains the Medicare premium interaction.
3. The IRMAA table changes by year. Confirm the current thresholds and the lookback year on the official sources before you convert.

Frequently asked questions

Does a Roth conversion increase IRMAA?

It can. The conversion raises modified adjusted gross income in the conversion year, and IRMAA uses that income two years later. Whether the tier changes depends on the amount and the thresholds.

Can I avoid IRMAA by converting after I retire?

Retirement may lower other income, which can leave more room before a cliff. It does not remove the conversion income from the lookback year or the two-year delay.

Is there a Roth conversion limit for IRMAA?

There is no special IRMAA conversion limit. The limit is the distance to the next income bracket. Convert more than the headroom and the surcharge can apply.

Does a backdoor Roth conversion count?

The tax treatment depends on the accounts and the steps used. Ask a tax preparer how the transaction is reported, and assume any income it creates can affect IRMAA.

Can I undo a conversion to lower IRMAA?

Recharacterizing a Roth conversion is generally not available under current rules. Do not assume a conversion can be reversed after the year ends. Ask a tax preparer before acting.

Do both spouses pay IRMAA after a conversion?

If both spouses are enrolled in Medicare and file a joint return, each may pay the surcharge based on the joint income. The household cost can be double the single estimate.

Source table

Figure	Value used	Official source
Part B standard premium	$202.90	CMS Part B premium fact sheetChecked October 28, 2026
First single threshold	$109,001.00	CMS Part B premium fact sheetChecked October 28, 2026
Second single threshold	$137,001.00	CMS Part B premium fact sheetChecked October 28, 2026
Roth conversion tax treatment	Reported in the conversion year	IRS Publication 969Checked October 28, 2026
Roth account rules	IRS retirement plan FAQ	IRS Roth account FAQsChecked October 28, 2026

What to do next

Before you convert, enter the pre-conversion income and the projected income in the IRMAA cliff checker. If the conversion crosses a line, use the How to lower IRMAA guide to compare timing options, and ask a tax preparer to model the combined tax and premium cost.