Most people understand that if they have spikes in income, it may spike where their income lands in their tax bracket. A sudden influx of cash from a bonus, a property sale, or a large retirement account withdrawal can easily push you into a higher marginal percentage. However, what most retirees fail to realize is that a spike in income can also significantly increase how much you have to pay in Medicare premiums. This surcharge can last throughout your retirement if your income remains consistently high.
Understanding how these spikes work is essential for anyone entering or currently in retirement. By managing your income effectively, you can avoid the “IRMAA trap.” This allows you to reduce your overall tax burden while also keeping your Medicare costs as low as possible for the rest of your life. This guide will walk through the mechanics of Medicare pricing, how income affects your monthly bills, and the specific strategies federal employees and other retirees can use to protect their hard-earned savings.
The Basics of Medicare Premiums and IRMAA
While Medicare Part A is generally free for those who have worked and paid into the system for at least ten years, Medicare Part B carries a monthly cost. For the year 2026, the standard base premium for Part B is $202.90 per month. This amount is what most beneficiaries pay, but it is not a flat rate for everyone. The government uses a system called the Income-Related Monthly Adjustment Amount, or IRMAA, to determine if you owe more.
IRMAA is a surcharge added to your Part B and Part D premiums if your income exceeds certain thresholds. Essentially, the more you earn, the more you pay for the exact same coverage. For a married couple, if your joint income remains under $218,000, you will likely only pay the base rate. However, as your income climbs into higher brackets, those premiums can escalate quickly. In the highest bracket, a single person could pay nearly $700 per month just for Part B.
How the Two-Year Look-Back Period Functions
One of the most confusing aspects of IRMAA is the timing. The Social Security Administration does not look at your current year’s income to determine your current premiums. Instead, they use a two-year look-back period. This means your 2026 Medicare premiums are actually based on the tax return you filed for the 2024 tax year. This delay can catch many new retirees off guard, especially if they had high earnings in their final years of employment.
Because of this look-back rule, a high-income year just before retirement can result in very expensive Medicare premiums during your first year of enrollment. It is a trailing cost that requires proactive planning. If you know you are two years away from Medicare eligibility, your financial decisions today are already impacting your future healthcare costs. Managing your Adjusted Gross Income (AGI) now is the only way to ensure you do not trigger these surcharges later.
Controllable Versus Fixed Income Sources
To manage your IRMAA exposure, you must distinguish between income you can control and income that is fixed. For many retirees, especially federal employees, sources like a pension or Social Security are fixed. Once these benefits begin, you generally cannot adjust the amount you receive each year. These form the “floor” of your income. If your pension and Social Security already put you close to an IRMAA threshold, you have very little room for error.
The biggest lever you can pull is your withdrawal rate from defined contribution plans like the Thrift Savings Plan (TSP) or traditional IRAs. Because withdrawals from these accounts are treated as ordinary income, a large distribution can easily push you over an IRMAA cliff. For example, taking $150,000 out of your TSP to pay off a mortgage might seem like a great way to reduce monthly expenses, but the resulting spike in income could trigger thousands of dollars in extra Medicare premiums.
The Hidden Cost of Roth Conversions
Many financial advisors recommend Roth conversions as a way to reduce future tax liability. By moving money from a traditional TSP or IRA into a Roth account, you pay taxes now in exchange for tax-free growth and tax-free withdrawals later. While this is often a brilliant long-term tax strategy, it carries a hidden Medicare cost. The amount you convert is added to your total income for that year, which can inadvertently trigger an IRMAA surcharge.
If you are planning a series of Roth conversions, you must look at the IRMAA brackets before deciding on the conversion amount. If your base income is $150,000 and the first IRMAA bracket starts at $218,000 for a married couple, you only have $68,000 of “room” to convert before you hit the surcharge. Crossing that line by even one dollar can result in both spouses paying significantly more for their healthcare for an entire year.
Managing Required Minimum Distributions (RMDs)
Even if you don’t need the money, the government eventually forces you to take distributions from your traditional retirement accounts. These are known as Required Minimum Distributions (RMDs). Typically starting between ages 73 and 75, RMDs can create a permanent spike in your income. If you have a large balance in your TSP or 401(k), your mandated distributions might be large enough to keep you in a high IRMAA bracket for the rest of your life.
This is why early planning is so critical. By strategically drawing down your traditional accounts or performing Roth conversions in the years before RMDs kick in, you can lower your future account balances. A smaller balance means a smaller RMD, which in turn gives you more control over your income and your Medicare premiums. Failing to account for RMDs often leads to a “tax torpedo” where high taxes and high Medicare premiums strike simultaneously.
When Part B Might Not Make Sense
While Medicare Part B is generally a good deal for the average retiree, the math changes for very high-income earners. If your income is consistently at the top of the charts and you are facing premiums of $700 per month per person, the value proposition of Part B weakens. This is particularly true for federal employees who already have robust Federal Employees Health Benefits (FEHB) coverage that they can carry into retirement.
However, you must be extremely careful before opting out. Some groups, such as those under the Postal Service or those using Tricare, are required by law to enroll in Part B to maintain their other benefits. If you aren’t required to join and your IRMAA surcharges are astronomical, you should run a detailed cost-benefit analysis. For the vast majority of people, the lower brackets make Medicare Part B a necessity, but the decision becomes much more nuanced at the highest income levels.