What is IRMAA, and how do I avoid it?

IRMAA stands for income-related monthly adjustment amount. It's a surcharge added to your Medicare Part B and Part D premiums when your income crossed a threshold, and the income it looks at is from your tax return two years ago. It works as a hard cliff, so one dollar over the line costs you the whole step. You avoid it by knowing where the lines sit before you take the income, and sometimes you cross one on purpose because the rest of the plan is worth more than the surcharge.

The letter that shows up two years late

Here's how most people meet IRMAA. A letter arrives from Social Security saying your Medicare premium is going up. You look at the number and you're mad. Nothing about your life changed. You didn't do anything this year.

Right, because it isn't about this year. Your surcharge for a given year is set by the income on the tax return from two years earlier. So a Roth conversion you did, or a property you sold, or a big required withdrawal, shows up on your premium two Januarys later. Long after you quit thinking about it.

That lag is why this catches people. It's also why it's plannable. The decision that triggers it is one you're making right now.

A cliff, and why one dollar really matters

Most of the tax code phases things in. You cross a line and something gets slightly less generous, gradually. That's a phase-out. It means you can be a little aggressive around the edges without much cost.

IRMAA doesn't work that way. It's a cliff. At exactly one dollar over the threshold, your premium jumps to the next tier for the whole year. Nothing gradual about it.

So the dollar genuinely matters here, in a way it almost never does elsewhere. When we model a conversion, this is one of the few places we care about the last few hundred dollars of income. Fill the bucket. Just watch the bucket while you pour.

The thresholds move every year, and they're different for a single filer than for a married couple filing jointly. Look them up rather than trusting a number you read once. Medicare's own page on costs carries the current tiers.

What actually counts toward the number

The measure is modified adjusted gross income, which for most people is their adjusted gross income plus any tax-exempt interest.

The pieces that usually move it in retirement are the ones you'd expect. Required withdrawals from pre-tax accounts. Roth conversion income. Capital gains from selling something. The taxable part of Social Security. Pension income. Interest and dividends in a taxable account.

What doesn't count is money coming out of a Roth, and money you take from a checking account or from principal you already paid tax on. That's the whole reason where your dollars live starts to matter more once Medicare is in the picture. Two households can spend the identical amount in a year and land in different tiers, purely because of which accounts the spending came from.

That's the same idea driving the withdrawal order question generally: which account you tap changes what your return says, even when your life looks the same.

The part people get wrong

This is the piece I most want somebody to take away, because the fear of IRMAA costs more than IRMAA does.

The surcharge looks back at one tax year. It shows up on your premium about two years later. And then it goes away. It doesn't follow you forward. If your income drops back below the line, your premium drops back with it, on the same two-year delay.

So it's a one-year event with a delayed arrival. That reframes the whole thing. You didn't earn a permanent penalty. You bought a single year's cost, and you can weigh it against what that year's decision bought you.

I've watched people turn down a conversion that was right for every other reason because of this. That's usually the more expensive choice. It's just quieter, and it plays out over a longer stretch.

When crossing the line on purpose is right

Sometimes the surcharge is worth paying.

The years between the last paycheck and the first required withdrawal are the most flexible tax years most people will ever have. Once required withdrawals start, they set a floor under your taxable income whether you want one or not, and that floor keeps climbing. So there's a real argument for converting aggressively during the window, even in years where you clear a Medicare threshold, because the alternative is a permanently higher income for the rest of your life.

That's a comparison, and it's specific to your numbers. The way to answer it is to run both paths out over the years you have left, rather than reacting to the one line you can see. Should I do Roth conversions has the short version of that decision, and Roth conversion dosage covers the how-much side. If you're doing this before Medicare has even started, Roth conversions before Medicare is written for exactly that stretch.

Worth saying: brackets in general feel like cliffs and mostly are not. Crossing into a higher bracket only taxes the income above the line at the higher rate. IRMAA is one of the few places where the intuition people have about brackets is actually true.

The appeal most people never hear about

If your income dropped because of a life-changing event, you can ask Social Security to use a more recent year instead.

Retirement itself counts. So do the death of a spouse, a divorce, a spouse's work stoppage or reduction, loss of income-producing property, and a few others. The form is SSA-44, and it exists precisely because the two-year lookback would otherwise charge a newly retired person a premium based on the last year they were still working full time.

That last case is common and it's worth knowing about the year you retire. A lot of people pay a surcharge they could have had adjusted.

So how do you avoid it

Know where the lines are before you take the income. Look at the whole retirement window instead of one year at a time. The tax picture between about 60 and 75 keeps changing underneath you, and the right move in one chapter is wrong two chapters later. Decide which account the money comes from with the threshold in view. And when a conversion or a sale would push you over, price the surcharge honestly against what you'd be giving up.

None of that works if the investments, the taxes, and the income plan are being handled by different people who never compare notes. The threshold sits right where all three meet, which is why they get decided together at one table. That's the Keystone method, and Medicare timing generally is covered in what I need to know about Medicare.

The cliff is real and the dollar counts. It's also one year, and one year is worth less than the rest of them.

Questions people ask when the Medicare letter arrives

Why did my premium go up when my income went down?

Because the premium is set by your return from two years ago. If your income has since dropped and it was a life-changing event like retiring, you can ask for a redetermination using a more recent year.

Does a Roth conversion count toward IRMAA?

Yes. Conversion income is ordinary income on your return, so it flows into the figure Medicare looks at. That's why conversions in the years right before and after 63 get modeled carefully.

Is the surcharge permanent once I trigger it?

No. It applies to one year's premiums, based on one year's return, and it comes off again when your income falls back below the threshold.

Do withdrawals from a Roth account count?

Qualified withdrawals from a Roth generally don't add to the figure. That's a large part of why building up money in a Roth before Medicare starts is worth something beyond the tax rate itself. Required withdrawals from pre-tax accounts do count, which is covered in what are required minimum distributions.

Keep exploring

Related reading on this site: Medicare what i need to know, Roth conversion should i, Roth conversions before medicare, Roth conversion dosage, What are required minimum distributions?, Keystone method.

When it helps, the free Roth Conversion Timing guide walks through the pieces in plain English, and you can start with a no-pressure Explore Call any time.

Sources

• Medicare: Part B and Part D costs, including the income-related adjustment tiers
• Social Security Administration: Medicare premiums and what to do if you disagree
• Social Security Administration: Form SSA-44, life-changing event request
• IRS: required minimum distributions from retirement plans and IRAs
• IRS: taxability of Social Security benefits

For discussion purposes only. This is general educational information and not individualized investment, tax, or legal advice. Medicare thresholds and premium tiers change every year, so confirm the current figures against the official sources above and review your own return with the right professional before you act.