What Is IRMAA? The Medicare Surcharge on Higher Incomes

IRMAA stands for income-related monthly adjustment amount. It is an extra amount added to your Medicare Part B and Part D premiums when your income is above a threshold.

That is the whole thing. Whose income triggers it, how much of it there is, and how it comes off again are the rest of this page.

One clarification before anything else, because it changes how you should think about the rest. IRMAA is not a tax. It is a reduction in a subsidy.

What does IRMAA actually stand for?

Income-related monthly adjustment amount. Social Security’s own regulation defines it as “an additional amount of premium that you will pay for Medicare Part B coverage if you have income above the threshold” (20 CFR §418.1010(b)(4)).

Notice the word “premium.” The government pays most of the cost of your Part B coverage, and your standard premium covers the rest. Under 42 U.S.C. §1395r(i)(1), a beneficiary whose income exceeds the threshold has that subsidy reduced, and the monthly premium increased by the same amount.

So the surcharge is not money taken from you. It is a discount you stop receiving.

That distinction sounds academic. It is not. It explains why the amount is set as a percentage of what Part B actually costs rather than as a flat fee, why it moves every year, and why it never appears anywhere on your tax return.

Is IRMAA a tax?

IRMAA is not a tax, and the differences are the practical ones.

Ordinary income tax is assessed by the IRS on the return you file. IRMAA is assessed by Social Security, on information the IRS forwards to it, and it is collected as part of your Medicare premium. It usually comes out of your Social Security check before you ever see it. If you are not yet drawing Social Security, Medicare bills you directly.

Income tax is graduated. Each slice of income is taxed at its own rate. IRMAA is not graduated at all, and that is the single most important thing to understand about it.

And income tax reaches everyone with taxable income. IRMAA reaches only people enrolled in Medicare Part B or Part D. If you are not enrolled, there is no premium to adjust, and your income is irrelevant to it.

Who does IRMAA apply to?

Three conditions have to hold at once.

You have to be enrolled in Part B, Part D, or both. Part B is outpatient medical coverage. Part D is prescription drug coverage, and the Part D surcharge is written into a separate subpart of the same regulation (20 CFR §418.2101), backed by its own statute at 42 U.S.C. §1395w-113(a). Part A, which most people receive premium-free, carries no income-related adjustment at all. Someone still working past Medicare age on employer coverage, who has delayed Part B, has nothing for the surcharge to attach to.

Your modified adjusted gross income has to be above the threshold. Not at it. Above it. The regulation calls the threshold “a level of modified adjusted gross income above which the beneficiary will have to pay the income-related monthly adjustment amount” (20 CFR §418.1105(a)). A household sitting exactly on the number pays the standard premium.

The income has to come from the tax year Social Security is looking at, which is not the year you are living in. It is the return from two years back, which is why the decision that causes a surcharge is always closed by the time the letter arrives. The look-back period has a page of its own, because the timing is where most of the confusion lives.

One structural point that surprises people: this is measured per person, not per household. Two spouses both enrolled in Part B each pay their own adjustment, calculated from the same joint return. The published amount is roughly half of what a couple feels.

The current thresholds and the dollar amount at each tier are in the 2026 IRMAA bracket article. They move every year, which is exactly why they are not on this page.

Why is IRMAA a cliff rather than a phase-in?

Because the adjustment is attached to a range, not to the dollars inside it.

Social Security determines which modified adjusted gross income range you fall into, and each range carries a fixed percentage of the unsubsidized Part B cost (20 CFR §418.1120(b)). Land anywhere in a range and you pay that range’s amount. There is no proration, no blending, and no partial credit for being near the bottom of it.

Compare that with the tax code. Cross into a higher tax bracket and only the dollars above the line are taxed at the higher rate. The first dollar over costs you a few cents. Under IRMAA, the first dollar over a threshold costs you the entire step up to the next tier, for twelve months, for each spouse enrolled.

I find a tollbooth is the right image. Which lane you are sent to is decided by a single number. The toll for that lane is identical whether you cleared the line by a dollar or by forty thousand.

This is also why IRMAA planning is a matter of inches rather than direction. Most tax planning asks how much income to create. IRMAA planning asks a narrower question: does the number land above a specific line or below it.

What income counts toward IRMAA?

Modified adjusted gross income, and the definition is specific.

Under 20 CFR §418.1010(b)(6), modified adjusted gross income is your adjusted gross income as defined by the Internal Revenue Code, plus five categories of tax-exempt income:

• Tax-exempt interest.
• Income from U.S. savings bonds used for higher education tuition and fees.
• Foreign earned income.
• Income from sources within Guam, American Samoa, or the Northern Mariana Islands.
• Income from sources within Puerto Rico.

Two consequences of that definition do most of the damage.

It starts from adjusted gross income, not taxable income. Adjusted gross income sits above your standard deduction on the return. Taxable income sits below it. They are never the same number, and the gap between them is the size of your deductions. A plan built around filling a tax bracket is aiming at the lower of the two figures while IRMAA measures the higher one.

Tax-exempt interest is added back in full. Municipal bond income is invisible to the income tax and completely visible to IRMAA. A portfolio built specifically to hold taxable income down can be carrying a Medicare problem that never appears on the tax return at all.

There is no separate list of what counts. Anything that lands in adjusted gross income is in. A Roth conversion, a realized capital gain, the sale of a rental property, a large required withdrawal from a retirement account. None of them are special cases. They are simply income, and income is what the measure reads.

The mirror image is just as useful. Money that never enters adjusted gross income never reaches this measure at all. A qualified Roth withdrawal and a return of basis are both outside it regardless of your age. The earnings portion of a non-qualified Roth withdrawal is not — it is includible in gross income, so it reaches this measure like any other income. So is a qualified charitable distribution from an IRA — but only once you have reached age 70½, since the distribution has to be made on or after that date to qualify (26 U.S.C. §408(d)(8)(B)(ii)), and there is an annual dollar cap on the amount excluded.

What each tier costs in dollars, and what one dollar over a line actually buys you, is on the 2026 bracket page.

If it helps to have the numbers in one place, I keep them all in the Ultimate Retirement Guide.

Does a high-income year mean a permanently higher premium?

A high-income year does not raise your premium permanently. This is the most reassuring fact about IRMAA, and the one people most often have backwards.

The determination is made fresh for each effective year — defined at 20 CFR §418.1010(b)(2) as the calendar year for which the adjustment is determined — against whatever tax year the IRS has most recently supplied. Nothing carries forward. A single unusual year raises your premium for the corresponding premium year, and then, absent anything else, falls away.

So a one-time event — a property sale, a conversion, a concentrated position finally liquidated — buys you one expensive year of Medicare premiums, not a permanent reclassification. That is a very different planning problem than a permanent one, and it is worth being precise about, because the fear of permanence talks people out of decisions that are actually worth making.

The exception is anything that repeats. A required minimum distribution from a large retirement account is not a one-time event. It arrives every year, grows with the account, and it is the version of this that genuinely does need planning years ahead of time.

Can you appeal an IRMAA determination?

Yes, and there are two separate routes. They are commonly described as one thing, and they answer different questions.

Reconsideration is the appeal. Under 20 CFR §418.1325, if you are dissatisfied with the initial determination about your income-related monthly adjustment amount, you may request that Social Security reconsider it. This is the route when you think the determination is simply wrong — the wrong tax year, the wrong filing status, a figure that does not match your return. Reconsideration runs on the standard Social Security review rules at 20 CFR §§404.907 through 404.922. Those rules set the filing window at 60 days after you receive notice of the initial determination (20 CFR §404.909(a)(1)), and an extension is available if you show good cause for missing it.

A new initial determination is the life-changing-event route. This is not an appeal. It is a request to have Social Security use a more recent tax year’s income instead of the year on file, and 20 CFR §418.1201 sets four conditions that must all be met. You experienced a major life-changing event. That event caused a significant reduction in your modified adjusted gross income. You ask for the more recent year to be used. And you supply the evidence.

The events are a closed list at 20 CFR §418.1205:

• Your spouse dies.
• You marry.
• Your marriage ends through divorce or annulment.
• You or your spouse stop working or reduce your hours.
• You or your spouse lose income-producing property through something outside your control, such as a disaster, arson, fraud, or theft.
• You or your spouse experience a scheduled cessation, termination, or reorganization of an employer’s pension plan.
• You or your spouse receive a settlement from an employer because of that employer’s closure, bankruptcy, or reorganization.

Retiring is on that list, under stopping work. A great many people pay a surcharge computed from a final working year’s salary and never learn that they could have asked for it to be recalculated.

The second condition matters as much as the first. Under 20 CFR §418.1215, a reduction in income is “significant” only if it moves you to a lower percentage on the table, or drops you below the threshold entirely. An event that changes your life but not your income does not qualify.

Form SSA-44 is how most people file the request. Its full name is the Medicare Income-Related Monthly Adjustment Amount — Life-Changing Event form. Social Security’s own manual describes the form as optional. The request can also be made in person at a field office (POMS HI 01120.001).

Two details from Social Security’s manual are worth carrying. The life-changing event may have occurred at any time in the past; there is no window that closes on you. The relief, however, does have timing: it generally starts in January of the year you make the request, so delay costs prior years. And a request applies only to the person filing it — if the same event affects both spouses, both have to file (POMS HI 01120.005).

And note what is not on the list. A Roth conversion is not a life-changing event. Neither is a property sale, a capital gain, an inheritance, or a strong year in the market. Those are choices and investment outcomes, and 20 CFR §418.1205 does not reach them; 20 CFR §418.1210 adds that events affecting your expenses but not your income, and losses from ordinary investment risk, specifically do not count.

There is one more route worth knowing, separate from both. If you amend the return Social Security used, you can provide the amended return and have the determination corrected retroactively, within three calendar years of the close of that tax year (20 CFR §418.1150).

What do people get wrong about this?

They think it is permanent. It is redetermined annually. One high year is one high year.

They think there is one MAGI. There are several, and they are not interchangeable. The definition that governs IRMAA is at 20 CFR §418.1010(b)(6). The one governing health insurance subsidies is different, and the provisional income calculation that decides how much of a Social Security benefit is taxable is different again.

They think crossing a threshold taxes only the excess. It charges the full tier.

They think it is a household cost. Both spouses on Medicare pay separately.

They think municipal bond interest is invisible. It is invisible to the tax and fully visible here.

They plan the income year and forget the premium year. The two are two years apart, and by the time the letter arrives the decision that caused it is long closed. Why the gap is two years, and which year is the first one that counts for you.

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IRMAA is one piece of what Medicare costs in retirement, and the piece most sensitive to decisions made years earlier. For this year’s thresholds and tier amounts, see the 2026 IRMAA brackets. For the timing — why the measure runs two years behind, and which birthday starts the clock for you — see the IRMAA look-back period. For everything around it — enrollment timing and the Part B late-enrollment penalty, coverage before Medicare age, and how premiums fit a withdrawal plan — start at Healthcare in Retirement.