IRMAA: How One Dollar of Income Can Raise Your Medicare Premium by Thousands

You probably think your Medicare premium is a fixed number. Everyone on Part B pays the same, and if your income creeps up a little, maybe your premium creeps up a little too. Reasonable. That is how almost everything else in the tax code works: brackets are marginal, so an extra dollar of income gets taxed at your rate, not your whole income.

IRMAA does not work that way.

IRMAA, the Income-Related Monthly Adjustment Amount, is a surcharge on Medicare Part B and Part D premiums. And it is a cliff, not a slope. Go one dollar over a threshold and you do not pay a little more on that dollar. You pay the full surcharge for that entire bracket, for both spouses if you are married, for the whole year.

That is why a single dollar of income can cost you thousands.

What is IRMAA and who pays it?

IRMAA is an extra amount added to your Medicare Part B and Part D premiums when your income exceeds certain thresholds. It is authorized under §1839(i) of the Social Security Act, administered by the Social Security Administration, and it hits anyone enrolled in Medicare whose income clears the first tier.

The base Part B premium for 2024 is $174.70 per month. If your income is under the first threshold, that is what you pay. Above it, IRMAA stacks a surcharge on top, and there is a separate Part D surcharge (added to whatever your drug plan already charges) on the same income schedule.

Two features make IRMAA sting more than people expect:

• It is per person. A married couple where both spouses are on Medicare pays the surcharge twice.
• It runs on a two-year lookback. Your 2024 IRMAA is based on your 2022 return, the most recent one on file when SSA runs the calculation.

That lookback is why IRMAA blindsides so many newly retired people. The year you had a big capital gain or sold a business is the year that sets your premium two years later, long after the money is spent.

What income counts toward IRMAA?

IRMAA uses your modified adjusted gross income, or MAGI, which for this purpose is your adjusted gross income plus tax-exempt interest. That last part surprises people.

Your MAGI for IRMAA is AGI (line 11 of your Form 1040) plus any tax-exempt interest reported on line 2a. Municipal bond interest that you bought specifically because it was "tax-free" still counts here. It is invisible to your income tax and fully visible to IRMAA.

Everything that inflates AGI is in play:

• Capital gains, including the one-time gain from selling a rental or a business
• Roth conversions (the converted amount is ordinary income the year you convert)
• Required minimum distributions from traditional IRAs and 401(k)s
• Taxable Social Security
• Tax-exempt muni interest, added right back in

What does not push you over: Roth withdrawals in retirement, return of principal, and the money itself once it is inside a Roth. That is the whole planning game.

Why is IRMAA a cliff instead of a slope?

Because the brackets are all-or-nothing. Once your MAGI crosses a threshold by any amount, you pay the surcharge for the entire bracket, not a prorated share.

Here is the arithmetic that catches people. Say the first IRMAA threshold for a married couple filing jointly is $206,000 of MAGI (2024, based on 2022 income). Land at $205,999 and you pay the base premium. Land at $206,001 and you owe the first-tier surcharge, which for 2024 adds $69.90 per month to Part B plus $12.90 per month to Part D, per person.

For a couple, that is roughly ($69.90 + $12.90) times two spouses times twelve months, or about $1,987 for the year. All triggered by crossing the line by two dollars.

The top bracket is worse. At the highest tier for 2024 (MAGI at or above $750,000 for a married couple), the Part B surcharge alone is $419.30 per month per person. That is over $10,000 a year for a couple, on top of the base premium.

The surcharge does not care whether you cleared the threshold by $1 or by $50,000. Same bracket, same bill.

The Roth conversion that cost $4,000 in premiums

A retired couple came to me in early spring, both 67, both on Medicare, married filing jointly. They had done what a lot of thoughtful retirees do: a Roth conversion in the prior year to fill up the 22 percent bracket before RMDs kicked in. Good instinct. Their advisor had run the income tax math carefully and the conversion made sense on the income tax alone.

Nobody ran the IRMAA math.

The conversion pushed their MAGI about $9,000 over the second IRMAA threshold. That single step moved them up two tiers instead of resting comfortably below the first. The two-year lookback meant the premium surcharge showed up the following year, right when they had forgotten the conversion ever happened. The added Part B and Part D surcharges across both spouses ran close to $4,000 for the year.

The conversion still may have been the right call over a lifetime. But if we had stopped the conversion $9,001 short of that threshold, they would have kept nearly all the tax benefit and skipped the surcharge entirely. The difference between a smart move and a smart move that quietly leaks $4,000 was a number nobody was watching.

Can you appeal or reduce IRMAA?

Yes, in two situations: a qualifying life-changing event, and a plain error in the income SSA used.

If your income dropped because of a specific life-changing event, you can ask SSA to use a more recent, lower year instead of the two-year-old return. You file Form SSA-44, "Medicare Income-Related Monthly Adjustment Amount - Life-Changing Event." The events SSA recognizes are specific and listed on the form:

• Marriage, divorce, or death of a spouse
• Work stoppage or work reduction (retirement counts)
• Loss of income-producing property
• Loss or reduction of a pension
• An employer settlement payment

Retiring is the big one. If your 2022 return reflected full salary but you stopped working in 2024, that is a work-stoppage event, and SSA-44 lets you get the surcharge recalculated on your new, lower income rather than the salary you no longer earn.

What is not a life-changing event: a one-time capital gain or a Roth conversion. Those are choices, and SSA treats them as such. You cannot appeal your way out of a conversion you elected to do. You can only plan around it before you pull the trigger.

How do you plan around the IRMAA cliff?

You watch the threshold before December 31, not after. IRMAA is a year-end problem that becomes unfixable on January 1.

A few moves that actually help:

• Know your bracket edges before you do anything discretionary. If a Roth conversion or a gain would push you $5,000 over a threshold, size it to land just under instead.
• Use qualified charitable distributions. A QCD from an IRA under §408(d)(8) (up to $105,000 in 2024) satisfies your RMD without adding to AGI, which keeps that income out of your IRMAA MAGI entirely.
• Spread out large gains across tax years where you can, rather than realizing everything in one spike.
• Remember the two-year lag when you retire. The year you stop working, plan for the premium bill that lands two years later, and file Form SSA-44 if a life-changing event applies.
• Coordinate the income tax plan and the IRMAA plan together. A conversion that is perfect on the income tax alone can still be a net loss once the surcharge lands.

If your income is close to a threshold and you are weighing a conversion, a property sale, or a large distribution, run both numbers before year-end. IRMAA is one of the few tax traps where being off by a single dollar has the same price as being off by fifty thousand.

Sources

• Social Security Act §1839(i) (income-related Part B premium adjustment)
• IRC §408(d)(8) (qualified charitable distributions)
• Form SSA-44, "Medicare Income-Related Monthly Adjustment Amount - Life-Changing Event"
• IRS Form 1040, line 11 (adjusted gross income) and line 2a (tax-exempt interest)
• CMS 2024 Medicare Part B premium and IRMAA amounts (base premium $174.70/month; surcharge and threshold figures for 2024)