Why is Medicare using my tax return from two years ago?

Because that is how the IRMAA lookback works: Social Security prices your Medicare premiums off the most recent tax return the IRS has given it, and that is normally the return from two years before the premium year. Your 2026 premiums are based on your 2024 tax return — not because Social Security thinks you still earn that much, but because 2024 is the newest complete tax year it has on file when it sets 2026 prices. If your income has dropped since then, you do not always have to wait for the system to catch up: a listed life-changing event lets you ask for a new determination now, using Form SSA-44.

The timeline, year by year

The gap feels strange the first time you see an IRMAA notice, because the notice talks about a year that is already over. But the sequence is mechanical: Social Security cannot price this year's premiums off this year's income — that tax return does not exist yet — so it reaches back to the most recent return the IRS has processed and shared.

The full official tables, for both years and every filing status, are on our 2026 brackets page.

The income number Social Security actually uses: MAGI

The figure that matters is not your salary, your total income, or the tax you paid. It is your MAGI — modified adjusted gross income — which for IRMAA means your adjusted gross income plus tax-exempt interest. That second piece surprises people: interest from municipal bonds, which you never pay regular income tax on, still counts toward IRMAA — enough of it can put a modest-pension retiree into a surcharge tier.

MAGI is also a household number when you file jointly: one MAGI from the joint return sets the tier for both spouses, and each spouse on Medicare pays that tier's surcharge.

Why the two-year gap exists

Three practical reasons stack up. Tax returns arrive on a lag: the return for a given year is filed the following spring, processed by the IRS, and only then shared with Social Security. Premiums for a calendar year are set in the fall of the year before, using whatever complete data exists at that moment. And the system is built for scale — premiums for tens of millions of people are priced from IRS data feeds, not individual updates. The lookback is the price of that automation: accurate eventually, stale by design in the year your life changes.

When your income has already dropped

This is where the lookback hurts most, and where the law gives you a door. If your income fell because of a life-changing event on Social Security's official list — marriage, divorce or annulment, death of a spouse, work stoppage or work reduction, loss of income-producing property beyond your control, loss of pension income, or an employer settlement payment — you can file Form SSA-44 and ask Social Security to price your premiums off a more recent year instead. It is a request for a new determination, not an appeal, and there is no 60-day deadline — but the reduction is anchored to the year you file, so asking in the same year your income dropped matters.

Two limits are worth knowing. First, the event is the whole case: a one-time income spike two years ago, like a house sale or a Roth conversion, is not itself a listed event, and "my income is lower now" by itself changes nothing. Second, your lower income still has to drop you into a lower tier — or out of IRMAA entirely — for the request to change your premium. Our life-changing events guide covers the borderline cases, and the free checker on the homepage tells you whether your situation fits.

The automatic step-down: when doing nothing works

If you simply wait, the system does correct itself — on its own schedule. When the IRS sends Social Security your newer, lower return, that return becomes the basis for the next premium year, and your surcharge steps down or disappears without any form, call, or request from you.

The catch is purely timing: you pay the higher, lookback-based premium in every month in between. That is the real choice the lookback puts in front of you — wait for the automatic step-down, or, if a listed life-changing event caused the drop, use Form SSA-44 to move the correction into the current year. If Social Security used the wrong data in the first place — an amended return it never applied, or IRS figures that were simply incorrect — that is a separate correction path that can reach back to the year the error affected.

Questions people ask

Why is my 2026 Medicare premium based on my 2024 taxes?

Because Social Security uses the most recent tax return the IRS has provided when it sets premiums, and for 2026 that is the return for tax year 2024 — the two-year lookback. It is the standard rule for everyone, not an error on your notice.

What income does Social Security look at for IRMAA?

Your MAGI: adjusted gross income plus tax-exempt interest, from the tax return for the lookback year. On a joint return, that one MAGI sets the tier for both spouses, and each spouse pays that tier's surcharge.

My income dropped this year. Do I have to wait two years for my premium to fall?

Not if the drop came from a listed life-changing event — retirement and work reduction are the most common. File Form SSA-44 to request a new determination based on the more recent year. Without a listed event, the lower income reaches your premium automatically once the newer return works through the lookback.

Will my premium go down on its own when my newer tax return shows lower income?

Yes. When Social Security receives the newer return from the IRS, it reprices the next premium year off that return, and a surcharge based on your old, higher income steps down or ends automatically. You do not need to notify anyone — but you pay the old rate until that premium year arrives.

Not financial or legal advice. Figures and rules here follow CMS and Social Security publications — the brackets page carries the full official tables and sources.