IRMAA Explained: The Medicare Surcharge Most People Never See Coming

Most people assume their Medicare premiums are the same as everyone else's. They aren't. If your income exceeds certain thresholds, you'll pay significantly more — based on a tax return you filed two years ago. Here's a clear explanation of how IRMAA works, why the timing catches people off guard, and what you can do about it.

What Is IRMAA?

IRMAA stands for Income-Related Monthly Adjustment Amount. It is a surcharge — an additional amount added on top of the standard Medicare Part B and Part D premiums — that applies to enrollees whose income exceeds certain thresholds set by the federal government.

The concept is straightforward: Medicare premium costs are income-adjusted. Higher earners pay more. Most people pay the standard premium. Those above the income thresholds pay the standard premium plus an IRMAA surcharge, which increases in steps as income rises.

IRMAA is not a penalty. It's not triggered by a mistake or a missed deadline. It's simply the mechanism Medicare uses to scale premiums to income — the same philosophy as income-based tax brackets, applied to healthcare premiums.

But understanding that IRMAA exists is only the beginning. The more important thing to understand is how Medicare determines whether you owe it — because the timing of that determination is where most people get caught flat-footed.

How IRMAA Is Calculated: The Income Threshold Structure

IRMAA applies to both Part B (medical insurance) and Part D (prescription drug coverage) premiums. The income thresholds and surcharge amounts are adjusted annually by the Centers for Medicare and Medicaid Services (CMS), so the exact figures change each year. What follows is an explanation of the structure — always verify current dollar amounts at Medicare.gov before making decisions.

Medicare determines your IRMAA tier by looking at your Modified Adjusted Gross Income (MAGI). MAGI for IRMAA purposes is your Adjusted Gross Income plus any tax-exempt interest income — the figure from your federal tax return.

There are five IRMAA tiers above the standard premium level, each applying a progressively larger surcharge to both Part B and Part D. As a general illustration of how the tiers are structured — with individual filer thresholds and approximate surcharge levels based on recent years:

Surcharge amounts shown are approximate, based on recent published figures. Income thresholds and amounts adjust annually. Always verify current figures at Medicare.gov or with the Social Security Administration.

A few things worth noting about this structure. First, IRMAA surcharges are per person. If you and your spouse are both on Medicare and both above the threshold, you each pay the surcharge independently — it's not a household figure. Second, the thresholds apply to both Medicare Advantage and Original Medicare enrollees. There is no way to structure your Medicare coverage to avoid IRMAA — if your income qualifies, you pay it regardless of which path you chose.

Third — and this is the part most people miss entirely — the income that determines your IRMAA tier isn't your income this year.

The Two-Year Lag: Why Last Year's Income Isn't the Problem

Here is the specific mechanic that surprises people most: Medicare does not use your current year's income to determine your IRMAA tier. It uses your income from two years prior, as reported on your federal tax return.

Your 2026 Medicare premiums are based on your 2024 tax return. Your 2027 premiums will be based on your 2025 return. This is called the two-year lookback, and it creates a timing mismatch that catches a specific group of people particularly hard: those who retired recently.

Consider the scenario. You spent most of your career as a physician, an executive, or a business owner. You earned a substantial income in 2024. You retired in early 2025. Your income dropped significantly — perhaps by 70 or 80 percent — the moment you stepped away from practice.

You turn 65 in 2026 and enroll in Medicare. You're now living on retirement income — Social Security, pension distributions, portfolio withdrawals — at a fraction of your former earnings. And yet Medicare looks at your 2024 tax return, sees the income from your final working year, and places you into a high IRMAA tier. You receive a bill for premium surcharges that reflect a financial reality from two years ago, not the one you're living today.

This isn't an error. It's how the system is designed. The Social Security Administration — which administers IRMAA on Medicare's behalf — simply uses the most recent tax return available. In most cases, that means a two-year lag between your actual financial picture and the income figure driving your premiums.

For people whose income has dropped significantly since that tax return was filed, the result can feel punishing. And for people who weren't expecting it at all — who assumed their Medicare premium would be the same standard amount everyone else pays — it can feel like a genuine shock.

The One Scenario Where the Lag Works in Your Favor

The two-year lookback cuts both ways. If your income was unusually low two years ago — due to a gap year, early retirement, a business loss, or a year with significant deductions — your IRMAA tier may be lower than your current income would otherwise suggest. Enjoy it. It won't last. The next year's determination will work from a more recent return.

This asymmetry matters for planning. If you're still working and Medicare is on your horizon, the income you report in the next two years will directly determine your premium costs when you enroll. That's not a reason to make bad financial decisions — but it is a reason to understand the timing before you get there.

What You Can Do About It: The Life-Changing Event Appeal

If your income has dropped significantly since the tax return Medicare is using, you're not without options. Medicare and the Social Security Administration allow you to request a redetermination — informally called an IRMAA appeal — based on a qualifying life-changing event.

The qualifying events that allow you to request a more recent income figure include: retirement or reduction in work hours, the death of a spouse, divorce or annulment, loss of income from income-producing property, loss or reduction of pension income, and employer settlement payment received due to the employer's closure or bankruptcy.

Notice what's on that list: retirement. If you stopped working and your income has dropped significantly since the tax year Medicare is using, you may be able to appeal and have Social Security use a more current income estimate instead. If approved, your IRMAA tier — and your premiums — will be adjusted accordingly.

The process involves filing Form SSA-44 (Medicare Income-Related Monthly Adjustment Amount — Life-Changing Event) with your local Social Security office. You'll need to provide documentation of the life-changing event and an estimate of your current modified adjusted gross income. The form is available at ssa.gov.

This isn't a guaranteed fix — Social Security will evaluate the request and the documentation — but for people who experienced a genuine, significant income change due to a qualifying event, it is a legitimate and often successful path to having premiums recalculated on a more current basis.

IRMAA Applies to Both Medicare Paths — Without Exception

One thing I want to be explicit about, because it occasionally causes confusion: IRMAA applies whether you choose Original Medicare + Medigap or Medicare Advantage. It is not a feature of one structure or the other. It is an overlay on top of Medicare itself.

If your income triggers IRMAA, you will pay the Part B surcharge regardless of which path you choose. If you have a standalone Part D plan (required under Original Medicare), you'll also pay the Part D IRMAA surcharge. If you're on Medicare Advantage and your plan includes drug coverage, the Part D surcharge still applies to you individually.

This matters because it means IRMAA should not influence your Medigap vs. Medicare Advantage decision. It's a fixed cost either way. The question of which path is right for you structurally — coverage flexibility, out-of-pocket exposure, geographic portability, long-term optionality — is entirely separate from IRMAA. Don't conflate them.

A Note on Planning Ahead

For people still a few years from Medicare eligibility, the two-year lag creates a planning window that's worth taking seriously — particularly in years with above-normal income events. The sale of a business. A large Roth conversion. A one-time distribution from a retirement account. Capital gains from a significant asset sale. Any of these can push your MAGI above an IRMAA threshold, and the premium impact will arrive two years later, right as you're entering Medicare.

I'm not a tax advisor, and this isn't tax planning guidance. But I would encourage anyone approaching Medicare to have a conversation with their financial advisor or CPA specifically about the two-year IRMAA lookback as part of pre-retirement income planning. The interaction between retirement timing, income recognition, and Medicare premium calculation is one of those areas where a little advance awareness can make a meaningful financial difference.

The Bottom Line

IRMAA is not a trap, and it's not unfair in its design. It's a straightforward income-scaling mechanism that most higher earners would recognize as consistent with how the broader tax system works. What makes it feel unfair — and what causes genuine financial disruption for people — is the two-year lag combined with the near-universal failure to explain it clearly before enrollment.

If your income is below the first threshold, IRMAA doesn't affect you and you can file this away as general awareness. If your income is above it — or if you're in the years immediately before Medicare with variable or elevated income — this is worth knowing now rather than discovering on your first premium statement.

And if you've recently retired and find yourself paying IRMAA surcharges based on income that no longer reflects your reality, the SSA-44 appeal process exists precisely for that situation. Use it.