What IRMAA is
IRMAA stands for Income-Related Monthly Adjustment Amount. It is an extra charge added to your Medicare Part B premium, and to your Part D drug coverage, when your income is above a set level. Everyone on Part B pays the standard premium, which is $202.90 a month in 2026. IRMAA is the amount on top of that.
CMS says these surcharges reach roughly 8% of people on Part B. That sounds small until you look at who is in that 8%: retirees with pensions, large IRAs, required minimum distributions, and anyone doing Roth conversions. In other words, the people who saved well.
The charge is per person. If you and your spouse are both on Medicare, you each pay it. The Part B portion is usually taken out of your Social Security check. The Part D portion is paid to Medicare, even if you pay your drug plan’s own premium to the insurance company. If you are on a Medicare Advantage plan, you still pay Part B, so IRMAA still applies.
The two-year lookback
Social Security sets your premium using the tax return from two years earlier. Your 2026 premiums are based on your 2024 return. That timing is the single most important thing to understand, because it means the income you create this year shows up as a premium bill two years from now.
| Income you report on your return for | Sets your Medicare premiums for |
|---|---|
| 2024 | 2026 |
| 2025 | 2027 |
| 2026 | 2028 |
| 2027 | 2029 |
Two things follow from this. First, a large Roth conversion in one year raises premiums for one year, two years later. It does not lock you into higher premiums permanently. Second, the lookback starts before Medicare does. If you enroll at 65, the income you report at 63 sets your first premium. Conversions done at 63 and 64 count.
What counts as income
Medicare uses modified adjusted gross income, or MAGI. For IRMAA, MAGI is your adjusted gross income from line 11 of Form 1040, plus any tax-exempt interest from line 2a. That second piece surprises people. Municipal bond interest is free of federal income tax, but it is not free of IRMAA.
Raises your IRMAA income
- Roth conversions
- IRA, 401(k), and TSP withdrawals, including RMDs
- Pensions and taxable annuity payments
- Wages and self-employment income
- Capital gains, including a home sale above your exclusion
- Interest and dividends
- The taxable part of your Social Security
- Tax-exempt municipal bond interest
Does not count
- Qualified Roth IRA withdrawals
- Qualified charitable distributions (QCDs) from an IRA
- HSA withdrawals used for qualified medical costs
- Spending money from savings or checking
- The nontaxable part of your Social Security
One more thing the calculator above accounts for: Social Security. Up to 85% of your benefits can become taxable, and how much depends on your other income. When you add a Roth conversion, part of your Social Security can become taxable at the same time. In that range, a $10,000 conversion can raise your AGI by $17,000 or more. If you use the “I know my AGI” option, the calculator cannot see this effect, so use “Build it for me” if you receive Social Security.
Why it’s a cliff
Income tax brackets are gradual. If you move into the next bracket, only the dollars above the line are taxed at the higher rate. IRMAA does not work that way. Cross a line by one dollar and you pay the full surcharge for that level, on every month of the year, for every person on Medicare in your household.
For a married couple both on Medicare, the first line costs $2,296.80 a year. The top level costs $13,872 a year.
Here is the math for the first line. Part B goes up $81.20 a month and Part D goes up $14.50 a month. That is $95.70 a month, times 12 months, which is $1,148.40 per person. Times two people, $2,296.80. At the top level, $487.00 plus $91.00 is $578.00 a month, times 12, times 2, which is $13,872.
2026 IRMAA brackets
These are the official 2026 figures from CMS. They apply to income from your 2024 tax return. The surcharge amounts below are per person, per month.
| Single filers | Joint filers | Part B total | Part B surcharge | Part D surcharge | Yearly, per person |
|---|---|---|---|---|---|
| $109,000 or less | $218,000 or less | $202.90 | $0.00 | $0.00 | $0 |
| $109,001 – $137,000 | $218,001 – $274,000 | $284.10 | $81.20 | $14.50 | $1,148.40 |
| $137,001 – $171,000 | $274,001 – $342,000 | $405.80 | $202.90 | $37.50 | $2,884.80 |
| $171,001 – $205,000 | $342,001 – $410,000 | $527.50 | $324.60 | $60.40 | $4,620 |
| $205,001 – $499,999 | $410,001 – $749,999 | $649.20 | $446.30 | $83.30 | $6,355.20 |
| $500,000 or more | $750,000 or more | $689.90 | $487.00 | $91.00 | $6,936 |
Married but filing separately, and lived with your spouse at any point in the year? The schedule is much harsher. Income at or below $109,000 pays no surcharge. Above $109,000 and below $391,000, you pay $446.30 for Part B and $83.30 for Part D. At $391,000 or more, $487.00 and $91.00. If you lived apart all year, use the single filer column.
IRMAA and Roth conversions
Most people ask the wrong question about IRMAA. They ask, “How do I avoid it?” The better question is, “What does crossing the line cost per dollar I convert, and is it worth it?”
Take a married couple, both on Medicare, with income of $156,200. They can convert $61,800 and stay under the first line. Suppose they convert $117,800 instead, filling the first IRMAA level all the way to its top at $274,000. The extra $56,000 they converted above the first line costs them $2,296.80 in premiums two years later. Divide one by the other: $2,296.80 ÷ $56,000 is about 4.1 cents on each of those dollars.
Now suppose they convert $62,800, just $1,000 over the line. Same $2,296.80 surcharge, spread over only $1,000. That is a 230% cost on those last dollars. Same couple, same line, wildly different result. The cliff punishes landing just over it. It barely matters if you go through it with purpose.
IRMAA is a cost to price, not a wall to stop at.
That is why the ladder in the calculator shows the cost per dollar above your free room. Compare that number to the income tax rate you expect to pay later on money left in a traditional IRA, including RMDs that keep growing, and the tax your heirs would pay on what is left. Sometimes staying under the line wins. Sometimes paying the surcharge for a year or two to get more money into a Roth sooner wins by a wide margin. It depends on your numbers, which is the point of running them.
The surviving spouse squeeze
When one spouse dies, the survivor usually files as single starting the year after. The income lines for single filers are half the joint lines. Income often does not fall by half. The survivor keeps the larger Social Security check, much of the pension, and all of the IRA and its RMDs.
A couple with $150,000 of income pays no IRMAA. A surviving spouse with the same $150,000 lands in the second level as a single filer. That is $202.90 plus $37.50, or $240.40 a month, which is $2,884.80 a year in surcharges that did not exist before. Roth conversions done while both spouses are alive, at the joint lines, are one of the main ways to soften this.
Appealing with Form SSA-44
Because Medicare looks back two years, the income it uses may not reflect your life today. If your income dropped because of a qualifying life-changing event, you can ask Social Security to use a more recent year by filing Form SSA-44. The qualifying events are marriage; divorce or annulment; death of a spouse; work stoppage; work reduction; loss of income-producing property; loss of pension income; and an employer settlement payment.
Retirement counts as work stoppage, and it is the most common reason people file. If you retired in 2025 and your 2024 income included a full salary, your 2026 premiums may be based on income you no longer have.
If Social Security denies the request, you can ask for reconsideration. You can also request a new determination if the IRS data they used was wrong or if you amended that year’s return.
Moves worth modeling
Every one of these depends on your numbers, so treat them as questions to run, not rules to follow.
Convert before the lookback starts. Income at 62 and earlier never touches a Medicare premium. Conversions in the years between retirement and 63 carry no IRMAA cost at all.
Size each year’s conversion to a line, with a cushion. Dividends, fund capital gain distributions in December, and interest can push you over a line you thought you cleared. Leaving a few thousand dollars of room is cheap insurance.
Use QCDs once you are 70½. Gifts to charity sent straight from your IRA count toward your RMD but do not count as income for IRMAA.
Watch the one-time spikes. A home sale above your exclusion, a business sale, or an inherited IRA payout can push you up several levels in one year. Spreading the income across years, or pairing it with a low-income year, can change the bill.
Plan for the survivor year. The lines halve when filing status changes. Model the survivor’s income, not just the couple’s.
Coordinate with your Social Security claiming age. Delaying benefits leaves room in your early 60s to convert while your income is low. Scott models these together, because the claiming decision and the conversion plan affect each other.
Sources
- CMS, 2026 Medicare Parts A & B Premiums and Deductibles (Nov. 14, 2025)
- Social Security Administration, Form SSA-44: Medicare IRMAA Life-Changing Event
- 2026 Medicare Trustees Report, projected 2027 Part B premium