A retirement-income decision can raise your Medicare premiums long before you see the bill. Learning how to estimate Medicare IRMAA helps you anticipate that cost before a Roth conversion, IRA withdrawal, stock sale, or final high-income working year changes your household cash flow.
IRMAA, short for Income-Related Monthly Adjustment Amount, is an additional monthly charge paid by higher-income Medicare beneficiaries. It applies to Medicare Part B and Part D. It is not a separate insurance policy or a one-time tax. It is a premium adjustment that can affect your monthly retirement budget for an entire year.
For retirees who have spent decades building 401(k), IRA, brokerage, and business assets, the issue is rarely whether they have saved enough. The practical question is how to coordinate withdrawals, taxes, Social Security, Medicare premiums, and required minimum distributions so more of their savings can support the lifestyle they want.
How to Estimate Medicare IRMAA Using the Two-Year Lookback
The starting point is understanding the timing. Medicare generally bases an IRMAA determination on the tax return from two years earlier. For example, your 2026 Medicare IRMAA is generally based on the modified adjusted gross income reported on your 2024 federal tax return.
That two-year lookback can surprise new retirees. You may enroll in Medicare after leaving work and living on a lower income, but Social Security may initially use a tax return from your final working years. If those years included a salary, bonus, deferred compensation payout, business income, or a large capital gain, your first Medicare premium may be higher than your current income suggests.
For IRMAA purposes, modified adjusted gross income, or MAGI, is generally your adjusted gross income from your federal return plus tax-exempt interest income. This distinction matters for Arizona households that own municipal bonds. Interest from many municipal bonds may be federally tax-exempt, but it can still count when Medicare calculates IRMAA.
Your filing status also matters. Medicare publishes different income ranges for single filers, married couples filing jointly, and married individuals filing separately. The married-filing-separately rules can be especially punitive in certain circumstances, so filing status should not be treated as a minor tax-preparation detail when Medicare planning is involved.
Find the Numbers That Drive Your Estimate
Begin with the federal tax return Medicare is most likely to use. Review the adjusted gross income reported on the return, then add tax-exempt interest. That total is your working estimate of IRMAA MAGI.
Next, compare that figure with the annual IRMAA income table for the Medicare year you are evaluating. The income thresholds and premium amounts change periodically, so use the table for the correct year rather than relying on an old article, a neighbor’s premium, or a prior Social Security notice.
Once you identify your income range, calculate both parts of the cost. Part B beneficiaries pay the standard monthly Part B premium plus any applicable IRMAA. For Part D, IRMAA is an added charge on top of the premium for your chosen prescription drug plan or Medicare Advantage plan that includes drug coverage.
A useful planning formula is:
Estimated annual Medicare cost = 12 × (Part B premium + Part B IRMAA + Part D plan premium + Part D IRMAA)
For a married couple, estimate the cost for each spouse. IRMAA is assessed individually, even though the income threshold for a couple filing jointly is based on household income. A few hundred dollars per month per person can become a meaningful annual expense, particularly when it arrives alongside rising property costs, travel plans, or support for family members.
Understand Why IRMAA Can Feel Like a Cliff
Income tax rates are progressive, meaning an additional dollar of taxable income is generally taxed at a marginal rate. IRMAA works differently. If your MAGI crosses into the next income range, the higher premium adjustment applies for the year. The extra income may be modest, but the added Medicare cost can be much larger than expected.
That does not mean you should avoid all income-producing decisions simply to stay below an IRMAA threshold. A Roth conversion may still provide meaningful long-term tax benefits. Selling a concentrated investment position may still reduce portfolio risk. Taking a larger IRA distribution may still be necessary to fund a purchase or meet your spending needs.
The key is to measure the full cost before acting. A decision that creates additional income may affect federal taxes, Arizona taxes, Social Security taxation, Medicare premiums, and future required minimum distributions. Looking only at the tax bracket can leave out a significant part of the picture.
Income Items That Commonly Trigger IRMAA
Retirees often associate IRMAA only with wages, but many forms of income can increase MAGI. Traditional IRA and 401(k) withdrawals are common drivers because distributions are generally included in taxable income. Required minimum distributions can become particularly consequential later in retirement, when account balances and annual withdrawal requirements may be substantial.
Roth conversions also increase taxable income in the conversion year. This can be a deliberate and appropriate strategy, especially during lower-income years before RMDs begin. But a conversion should be modeled with its Medicare effects included, particularly when you are close to an IRMAA threshold.
Other common sources include realized capital gains, dividends, interest, rental income, business income, taxable Social Security benefits, and gains from the sale of real estate or investments. A one-time event can be enough to create an IRMAA surcharge for a future Medicare year.
Consider a couple who retires in 2026 after a strong final year of earnings in 2024. Their 2024 return may also include a bonus, stock-option income, and gains from selling an investment property. When they enroll in Medicare, their initial premium may reflect that earlier income rather than the lower retirement income they expect to live on. Estimating the surcharge in advance allows them to budget accurately and determine whether they may qualify to request a new determination.
When You May Be Able to Appeal an IRMAA Decision
A higher Medicare premium is not always final. Social Security may reconsider an IRMAA determination after certain life-changing events that substantially reduce your income. Retirement or a reduction in work are among the most common situations for new Medicare beneficiaries. Other qualifying events may include the death of a spouse, divorce or annulment, loss of income-producing property due to circumstances beyond your control, or loss of certain pension income.
The appeal is generally requested through Social Security using Form SSA-44, along with documentation supporting both the qualifying event and your estimated lower income. A retirement letter, final pay information, pension statement, or tax documentation may be relevant depending on the circumstances.
An appeal is not designed for every high-income year. A voluntary Roth conversion, large IRA withdrawal, or investment gain generally does not become appealable simply because it produced a higher premium. Still, when IRMAA is based on income that no longer reflects your financial reality after retirement, a timely review can be worthwhile.
Build IRMAA Into Your Retirement Income Plan
The best time to address Medicare premium exposure is before an income decision reaches your tax return. A multi-year retirement plan can project expected wages, Social Security, pension income, RMDs, investment income, capital gains, and planned Roth conversions. From there, you can estimate whether a proposed decision moves you into a higher IRMAA range and whether the long-term benefit justifies the cost.
There is no universal rule that says staying under an IRMAA threshold is always best. In some years, paying a higher premium can be the reasonable trade-off for reducing future RMDs, creating tax-free Roth assets, or managing a large future tax liability. In other years, spreading income across multiple tax years may better protect cash flow and preserve flexibility.
This is where coordinated tax and retirement planning matters. Roberts Tax & Retirement Planning helps households evaluate retirement decisions through the connected lens of income needs, taxes, Medicare premiums, Social Security, and long-term asset stewardship.
Before making your next large retirement-income move, put the Medicare cost beside the tax estimate and the cash-flow plan. A decision made with that full view can help your future self keep more control over the retirement you worked to build.
