IRMAA: How Your Income Affects Medicare Premiums

Most people assume everyone pays the same amount for Medicare. Then a letter arrives from Social Security announcing that their premiums will be hundreds of dollars higher than their neighbor’s, and the acronym IRMAA enters their vocabulary for the first time. It is one of the most common surprises we see among Winchester retirees, especially in the first year or two after leaving a good career.

IRMAA is not a penalty and it is not a mistake, but it is confusing, and the rules behind it reward people who understand them ahead of time. This article explains what IRMAA is, how the brackets work, and why a decision you make this year can show up on your Medicare bill two years from now. It is general education only, not advice for your personal situation.

What is IRMAA and who has to pay it?

IRMAA stands for Income Related Monthly Adjustment Amount. It is a surcharge added on top of the standard Medicare Part B and Part D premiums for people whose income exceeds certain thresholds. For 2026, the surcharge generally begins once modified adjusted gross income passes roughly $109,000 for a single filer or $218,000 for a married couple filing jointly, with the thresholds adjusted each year.

Most Medicare enrollees never pay it, since the large majority of retirees fall below the first threshold. For those above it, the surcharges climb through several brackets and can add anywhere from about $80 to more than $500 per person per month across Part B and Part D at the highest tier. Because it applies per person, a married couple can effectively pay the adjustment twice.

The two year lookback catches people off guard

Here is the piece that surprises almost everyone: IRMAA is based on your tax return from two years ago. Your 2026 Medicare premiums are set by the income on your 2024 return, because that is the most recent return the IRS had fully processed when Social Security ran the numbers. The income that matters is called modified adjusted gross income, which in plain terms is your adjusted gross income plus any tax exempt interest, such as municipal bond income.

The practical effect is a lag between your life and your premium. Someone who retires from a strong salary in 2025 can spend 2026 living on far less while paying surcharges based on their final working years. The reverse is also true: income spikes today, from whatever source, quietly set up higher premiums two years down the road. Understanding the lag is half of understanding IRMAA.

The brackets are cliffs, not ramps

IRMAA brackets work differently than tax brackets, and the difference matters. With income taxes, only the dollars above a threshold get taxed at the higher rate. With IRMAA, crossing a threshold by even one dollar triggers the full surcharge for that entire bracket, for the entire year. There is no proration and no partial adjustment. One dollar of extra income can genuinely cost a couple more than a thousand dollars in added premiums.

This cliff structure is why the people who study IRMAA pay so much attention to where their income lands in any given year. Common events that push retirees over a line include large withdrawals from retirement accounts, converting money from a traditional IRA to a Roth IRA, selling a home or investment property with a big gain, and required minimum distributions, which are the withdrawals the IRS requires from most retirement accounts starting in your 70s.

You can appeal when life changes

Because of the two year lookback, Social Security provides an appeal process for people whose income has dropped due to a life changing event. Qualifying events include retirement or reduced work hours, marriage, divorce, the death of a spouse, and a few others such as losing a pension. If one applies, you can file Social Security’s life changing event form and ask them to use your current, lower income instead of the two year old return.

This appeal is routine and widely used, especially by new retirees. Someone who stops working in December and starts Medicare with premiums based on peak salary years is exactly who the process exists for. What does not qualify is simply having one unusually high income year from an investment sale or conversion. Those adjustments stand, which is why the planning conversation ideally happens before the income event, not after the letter arrives.

Why IRMAA belongs in retirement income planning

None of this means higher earners should avoid income, and paying IRMAA for a year is sometimes the natural byproduct of a sensible move. The point of understanding the brackets is simply awareness of timing. People often discuss with their advisors how the timing of account withdrawals, conversions, charitable giving from retirement accounts, and property sales interacts with the thresholds, since the same dollars taken in a different year can produce a different premium outcome.

For Winchester retirees, the takeaway is that Medicare premiums are connected to your tax return, and the connection runs on a two year delay with hard cutoffs. Any year that includes retirement, a large sale, a conversion, or a change in marital status is a year worth mapping against the brackets. That is a planning exercise, not a form you fill out after the fact.

Bottom Line

IRMAA is a monthly surcharge on Medicare Part B and Part D premiums for higher income households, based on your tax return from two years prior, with bracket thresholds that operate as all or nothing cliffs. Life changing events like retirement can be appealed, but one time income spikes generally cannot. The rules are the same for everyone, yet the right moves depend entirely on your own income picture, so talk through your specific situation with a licensed professional before acting. The team at Clarity Insurance & Retirement in Winchester walks through these numbers with local families every week.

Related reading: our medicare planning enrollment services, Long Term Care Insurance Basics, How HSAs Work in Retirement