For many federal retirees, the Income-Related Monthly Adjustment Amount (IRMAA) comes as an unexpected layer of healthcare costs. While Medicare is often thought of as a uniform benefit, IRMAA introduces income-based pricing that can significantly increase monthly healthcare expenses for higher-income retirees.
Understanding how IRMAA is calculated, what income counts, and how timing decisions affect future premiums is essential for effective retirement planning.
How IRMAA Is Calculated
IRMAA is based on your Modified Adjusted Gross Income (MAGI), not simply your taxable income or adjusted gross income alone. For Medicare purposes, MAGI is generally defined as your adjusted gross income (AGI) from your federal tax return plus any tax-exempt interest income, such as municipal bond interest.
The Social Security Administration uses a tiered system to determine whether you will pay IRMAA and how much you will pay. If your MAGI exceeds a certain threshold, you are assessed a surcharge on top of your standard Medicare Part B and Part D premiums. These surcharges increase as income rises, creating distinct “brackets” rather than a gradual phase-in.
In 2026, for example, the first IRMAA threshold begins at $109,000 for individuals and $218,000 for married couples filing jointly, based on MAGI.
The Two-Year Lookback Rule
One of the most important (and often misunderstood!) features of IRMAA is the two-year lookback period.
Your 2026 IRMAA determination is not based on your current income in 2026. Instead, it’s actually based on your 2024 tax return. Similarly, your 2027 IRMAA will be based on your 2025 income, and so on. This delay exists because Medicare relies on finalized IRS tax data, which means there is always a lag between when income is earned and when it affects Medicare premiums.
The practical implication here is significant: financial decisions made today can impact Medicare costs two years in the future. A Roth conversion, large capital gain, or spike in retirement account withdrawals may not affect premiums immediately, but the impact will show up later, often at a time when retirees are no longer actively earning income.
What Income Counts Toward IRMAA
Because IRMAA is based on MAGI, many common sources of retirement income can push retirees into higher brackets. These include traditional IRA and 401(k) withdrawals, Required Minimum Distributions (RMDs), pension income, taxable Social Security benefits, capital gains, dividends, and interest income.
Even income that is not federally taxable—such as municipal bond interest—is included in MAGI for IRMAA purposes. This often surprises retirees who assume tax-free income is excluded from Medicare calculations.
As a result, retirement income planning becomes less about minimizing taxes in isolation and more about managing total MAGI across multiple years.
Why Timing Matters: Roth Conversions and Retirement Transitions
For federal retirees, the period between retirement and the start of Required Minimum Distributions (typically age 73) is often a critical planning window.
During this time, income may temporarily drop, creating opportunities for Roth conversions at lower tax rates. However, these conversions increase MAGI in the year they are executed, which can trigger higher IRMAA premiums two years later.
This creates a trade-off: Roth conversions can reduce future taxes and RMDs, but they may increase Medicare premiums in the short term. Effective planning requires balancing long-term tax efficiency against near-term IRMAA exposure.
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The “Cliff” Effect of IRMAA
IRMAA is also structured as a cliff system rather than a smooth phase-in. This means that even a small amount of income above a threshold can push an entire year’s premiums into a higher bracket.
For example, exceeding a threshold by even one dollar can trigger significantly higher Medicare premiums for the entire year. This makes precise income control especially important for retirees near bracket boundaries.
FEHB Coverage and BCBS Basic Considerations
Many federal retirees remain enrolled in the Federal Employees Health Benefits (FEHB) program after enrolling in Medicare, and coordination between the two systems plays an important role in managing out-of-pocket healthcare costs.
The Blue Cross Blue Shield Service Benefit Plan Basic Option is one of the most commonly used FEHB plans among retirees. While it does not eliminate IRMAA, it can help offset some of the additional costs associated with Medicare premiums. However, it is important to understand that FEHB plans do not reimburse IRMAA directly in most cases.
Instead, some FEHB plans offer premium reimbursements or Medicare Part B premium reductions that can partially offset Medicare costs. In certain cases, these reimbursements may help reduce the net impact of IRMAA, but they rarely cover the full surcharge amount.
Other FEHB plans may provide more generous Medicare coordination benefits, including partial reimbursement of Part B premiums or additional cost-sharing advantages for retirees enrolled in Medicare. These benefits can effectively reduce overall healthcare costs, even though they do not directly eliminate IRMAA obligations.
Because plan benefits vary significantly, retirees should evaluate FEHB options not only based on premiums and coverage, but also on how each plan coordinates with Medicare and whether it provides any form of premium reimbursement that could indirectly offset IRMAA exposure.
Planning Strategies to Manage IRMAA Exposure
Although IRMAA cannot be avoided entirely for higher-income retirees, it can often be managed with careful planning. Strategies such as smoothing income over multiple years, timing Roth conversions strategically, harvesting capital gains in lower-income years, and coordinating withdrawals across accounts can all help reduce MAGI volatility.
Charitable giving strategies, such as Qualified Charitable Distributions from IRAs once eligible, can also reduce taxable income while satisfying charitable goals.
The key principle is that IRMAA planning is not a one-year decision. Because of the two-year lookback, every tax decision has a delayed impact, making multi-year planning essential.
IRMAA adds a layer of complexity to Medicare that many retirees don’t anticipate until they receive their first premium notice. Because it is based on a two-year lookback and tied to MAGI rather than taxable income, it can be influenced by a wide range of financial decisions.
For federal employees and retirees, the most effective approach is to integrate IRMAA considerations into broader retirement income planning. By understanding how income flows translate into future Medicare costs and how FEHB coordination may offset some expenses, retirees can make more informed decisions and reduce unexpected premium increases over time.
The information has been obtained from sources considered reliable but we do not guarantee that the foregoing material is accurate or complete. Any opinions are those of Serving Those Who Serve writers and not necessarily those of RJFS or Raymond James. Any information is not a complete summary or statement of all available data necessary for making an investment decision and does not constitute a recommendation. Investing involves risk and you may incur a profit or loss regardless of strategy suggested. Every investor’s situation is unique and you should consider your investment goals, risk tolerance, and time horizon before making any investment or financial decision. Prior to making an investment decision, please consult with your financial advisor about your individual situation. While we are familiar with the tax provisions of the issues presented herein, as Financial Advisors of RJFS, we are not qualified to render advice on tax or legal matters. You should discuss tax or legal matters with the appropriate professional. **
