Does a Roth Conversion Raise Your Medicare Premiums? How IRMAA's Two-Year Lookback Works

Medicare premiums are not the same for everyone. If your income is above certain thresholds, you pay more for Medicare Part B and Part D, and a Roth conversion, a large capital gain, or a big required distribution can push income over a line without anyone noticing until the bill arrives. This article explains how the surcharge works and what to ask before a conversion. It is general education, not advice for your situation.

What is IRMAA?

IRMAA stands for Income-Related Monthly Adjustment Amount. It is an extra amount added to the standard Part B premium (and to Part D drug coverage premiums) for people whose income is above set thresholds. For 2026, the standard Part B premium is $202.90 per month, and higher-income enrollees pay more, up to $689.90 per month in total at the top tier.

The Social Security Administration (SSA) makes the IRMAA determination, using tax information from the IRS. See the SSA's Medicare premiums information for how it works.

Which year's income counts toward IRMAA?

The SSA uses your modified adjusted gross income (MAGI), which is your adjusted gross income plus tax-exempt interest, from your federal tax return. Per the SSA's Form SSA-44, the SSA asks the IRS for your return from two years back: for 2026 premiums, that is tax year 2024, and if that return is not available, it uses tax year 2023. Following the same pattern, income reported on your 2025 return generally sets 2027 premiums, and 2026 income generally affects 2028. This delay is why a decision made in December can show up on a Medicare bill more than a year later.

What are the IRMAA income thresholds?

The surcharge is tiered. The 2026 thresholds published by CMS are:

Single MAGI	Joint MAGI	Total monthly Part B premium
Up to $109,000	Up to $218,000	$202.90
$109,001 to $137,000	$218,001 to $274,000	$284.10
$137,001 to $171,000	$274,001 to $342,000	$405.80
$171,001 to $205,000	$342,001 to $410,000	$527.50
$205,001 to under $500,000	$410,001 to under $750,000	$649.20
$500,000 or more	$750,000 or more	$689.90

Thresholds are adjusted each year, and CMS typically publishes the next year's figures in the fall, so the 2027 numbers may differ. Part D carries its own separate surcharge. Each spouse enrolled in Medicare pays the surcharge individually.

A note worth highlighting: IRMAA works in tiers. Income that lands even slightly above a threshold moves you into that tier's full surcharge for the year, rather than a partial one.

How can a Roth conversion affect IRMAA?

When you convert pre-tax IRA money to a Roth IRA, the converted amount is added to your taxable income for that year (see our article on when Roth conversions make sense). Higher income can mean a higher MAGI, which can mean a higher tier two years later. Other income sources can do the same, including required minimum distributions, realized capital gains, and the taxable portion of Social Security.

Whether a conversion actually crosses a threshold depends on your filing status, your other income, and the size of the conversion. Some people convert in measured amounts across several years, while others find the surcharge is a small part of the overall tax picture. Which approach fits depends on your specific numbers, and it is worth modeling before you act.

Can you appeal an IRMAA determination?

In some cases, yes. If you had a qualifying life-changing event and your income went down as a result, you can ask the SSA to use a more recent tax year by filing Form SSA-44 (you can also call 1-800-772-1213). The events listed on the form are:

• Marriage
• Divorce or annulment (where you will not file a joint return with your spouse for the year)
• Death of your spouse
• Work stoppage or reduction (you or your spouse stopped working or reduced hours)
• Loss of income-producing property not at your direction, such as from a declared disaster, fraud, or theft
• Loss of pension income from a scheduled cessation, termination, or reorganization of an employer's pension plan
• An employer settlement payment related to the employer's bankruptcy or reorganization

The SSA requires evidence of both the event and your more recent income. Because the form's list covers events such as work stoppage and does not list income changes you chose to create, such as a Roth conversion, a realized capital gain, or a large distribution, do not assume those will qualify. The SSA decides each request, so review the form's instructions.

What questions should you ask before converting?

• Which MAGI tier am I in today, and how close am I to the next one?
• Does my conversion plus other income this year cross a threshold?
• Do I have an upcoming life event that could lower future income?
• Is the potential surcharge outweighed by the tax benefit I am trying to capture?

Your tax professional or fiduciary advisor can help weigh these together with your bracket, withdrawal order, and long-term goals.

The bottom line

IRMAA is one of several costs that can accompany a rise in income in retirement. It is not a reason to avoid planning, but it is a reason to look at a multi-year picture before making a decision that cannot be undone. Your results depend on your income, filing status, and timing.

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