How Medicare IRMAA Surcharges Work

Medicare IRMAA — the income-related monthly adjustment amount — raises Part B and Part D premiums for people above certain income levels. It is a surcharge rather than a tax, it is not means-testing in any gradual sense, and it has two features that make it a genuine planning problem rather than a line item.

It uses income from two years ago, and it works as a cliff.

The two-year lookback

Your premium this year is set by the income on your tax return from two years prior.

That means the surcharge arrives when the income that caused it is long gone — often after retirement, based on a final working year. Someone who retires at 65 pays premiums at 67 based on their income at 65, which may have included a final salary, a severance payment, or the sale of a business.

The planning consequence is uncomfortable but clear: decisions you make today set premiums you will not see for two years. A Roth conversion at 63 shows up as a higher premium at 65. By the time the bill arrives, the opportunity to do anything about it has passed.

This is also why people are so often blindsided. The connection between the action and the consequence is separated by long enough that it is not obvious.

Medicare IRMAA uses cliffs, not brackets

This is the part that costs the most money and it runs against ordinary tax intuition.

Income tax is graduated: crossing a bracket boundary means only the dollars above it are taxed at the higher rate. Nothing dramatic happens.

The Medicare IRMAA tiers do not work that way. One dollar over a threshold moves you into the next tier entirely, and the higher premium applies to the whole year.

So a single dollar of extra income can cost hundreds or thousands. And because the surcharge applies to both Part B and Part D, and to each spouse separately, a couple crossing a threshold pays the increase twice.

That is a marginal rate on one dollar that is effectively enormous, and it is why the Medicare IRMAA calculator is worth running before any deliberate income event rather than after.

The tiers are indexed and republished annually, so check the current figures with Medicare rather than working from remembered numbers.

What counts toward the income figure

The measure is modified adjusted gross income — adjusted gross income plus tax-exempt interest. Several things follow.

Municipal bond interest counts, despite being exempt from income tax. This surprises people who hold municipals specifically to keep income down. The tax equivalent yield calculator should be read with that in mind for anyone near a threshold.

Traditional withdrawals and required distributions count in full. As balances grow, required distributions can push a household over a threshold without any decision being made at all.

Capital gains count, including the one-off kind. Selling a rental property or a long-held stock position can trigger a surcharge two years later.

Roth withdrawals do not count. This is the single most useful fact here, and it is the strongest argument for holding some tax-free balance into retirement — it is the only pocket you can spend from without moving the figure. The withdrawal sequencing guide covers using that lever deliberately.

A Roth conversion counts in the year of conversion. Conversions are among the most common causes of an unexpected surcharge, which is a real tension: the low-income years ideal for converting are also the years setting future premiums. The Roth conversion guide covers sizing a conversion against the threshold rather than into it.

The appeal that most people do not know about

If your income has dropped because of a life-changing event, you can ask for the surcharge to be recalculated using current income instead of the two-year-old figure.

The qualifying events are specific and include retirement or reduced work hours, marriage, divorce, death of a spouse, loss of a pension, and loss of income-producing property.

Retirement is on that list, and this is the single most valuable thing to know here. The most common IRMAA scenario is someone retiring and then being charged a surcharge based on their final working year. That is exactly what the appeal exists for, and a large number of people simply pay it instead.

The process is a form — SSA-44 — plus evidence of the event and an estimate of current income. It is administrative rather than adversarial, and it is decided quickly.

Note what does not qualify: a one-off capital gain, or a Roth conversion. Voluntary income events are not life-changing events, so the surcharge on a deliberate conversion stands. That asymmetry is worth knowing before converting.

Planning around the thresholds

Check before acting, not after. Any deliberate income event — a conversion, a property sale, harvesting gains — should be sized against the threshold first. The two-year lag means there is no correction later.

Fill to just below the line. The correct amount to convert is frequently the space remaining under a threshold, not the space remaining in a tax bracket. Whichever binds first is the real constraint.

Spread events across years. Selling a property in one year may cross two tiers. Structuring an instalment sale, or splitting a conversion across two years, can keep each year under the line.

Use Roth and taxable-basis withdrawals in high-pressure years. Spending from accounts that generate little reportable income keeps the figure down without reducing what you actually spend.

Give from the IRA if you are charitable. A qualified charitable distribution satisfies a required distribution without entering income at all, which is one of the few ways to reduce the figure rather than merely avoid raising it.

Watch the first year of Medicare specifically. The overlap of a final working year, a possible severance, and the start of premiums makes this the most likely year to be caught — and the most likely to qualify for an appeal.