Most people spend decades planning for retirement income. Very few plan for retirement expenses they didn't know existed. IRMAA is one of those expenses. IRMAA stands for Income-Related Monthly Adjustment Amount. It's a surcharge added to your Medicare Part B and Part D premiums when your income exceeds certain thresholds. It is not a small surcharge. Depending on your income, it can add anywhere from $1,148 to nearly $6,932 per year to your Medicare costs — per person. The majority of people who pay it had no idea it was coming. And the reason it catches people off guard is the rule that dr
Every fall, the Social Security Administration sends out IRMAA determination notices for the following year. Those notices are based on the most recently available tax return — which is typically two years old. Your 2026 Medicare premiums are calculated from your 2024 tax return, filed in 2025. This two-year look-back creates a gap between when income is earned and when it affects Medicare costs. A large Roth conversion in 2024 doesn't raise your 2024 or 2025 Medicare bill. It raises your 2026 bill. By the time the surcharge arrives, many retirees have no memory of — or connection to — the income event that caused it.
IRMAA operates on a cliff system — not a graduated one. Standard income taxes apply only to income above a threshold. IRMAA applies to your entire premium tier the moment you cross a line by even one dollar. 2024 MAGI 2024 MAGI Part B Annual Extra (Single) (Joint) Monthly Cost (Single) ≤ $109,000 ≤ $218,000 $202.90 $0 — baseline > $109,000 > $218,000 $284.10 ~$974/yr $137,000 $274,000 > $137,000 > $274,000 $405.80 ~$2,436/yr $171,000 $342,000 > $171,000 > $342,000 $527.50 ~$3,894/yr $205,000 $410,000 > $205,000 > $410,000 $649.20 ~$5,354/yr $499,999 $749,999 ≥ $500,000 ≥ $750,000 $689.90 ~$5,844/yr Source: CMS 2026 Medicare Part B premium schedule. Thresholds based on 2024 MAGI (two-year look-back). Part D surcharges apply separately and add additional annual cost at each tier. For married couples, each spouse pays the applicable surcharge separately. Crossing the first joint tier at $218,001 costs both spouses the Tier 1 surcharge — a combined additional cost of roughly $1,948 per year for Part B alone, plus Part D surcharges.
One of the most common mistakes in IRMAA planning is treating Adjusted Gross Income (AGI) and Medicare MAGI as interchangeable. They're not. For IRMAA purposes, your Modified Adjusted Gross Income starts with your AGI — Line 11 of your Form 1040 — and then adds back any tax-exempt interest income, such as interest from municipal bonds. That add-back surprises many retirees who hold municipal bonds specifically to reduce their taxable income, unaware that the same interest is fully counted for IRMAA purposes. The formula: Medicare MAGI = AGI + tax-exempt interest income. If your AGI is $105,000 and you received $8,000 in municipal bond interest, your Medicare MAGI is $113,000 — above the first tier threshold even though your taxable income is below it.
IRMAA is not only triggered by investment income or salaries. Any event that raises MAGI in the look-back year can produce a surcharge two years later. The most common triggers: Roth conversions: The converted amount is added to ordinary income in the year of the conversion. A $100,000 conversion in a year when other income is already at $140,000 can push a single filer into Tier 3 or higher. Required Minimum Distributions: For retirees with large traditional IRAs, annual RMDs can push MAGI over a threshold year after year — making IRMAA a permanent structural cost rather than a one-time event. Capital gains realizations: Selling appreciated stock, rebalancing a brokerage account, or receiving mutual fund capital gains distributions all increase MAGI. 'Phantom income' from fund distributions — where a capital gain is distributed to investors who didn't actively sell anything — can trigger IRMAA without the investor realizing it. Property sales: The IRS excludes up to $250,000 ($500,000 for couples) of gain from the sale of a primary residence. But a second home, rental property, or vacation property generates fully taxable capital gains, which can spike MAGI in the year of sale.
IRMAA is not a tax. It's a Medicare premium surcharge. It does not|Municipal bond interest is tax-exempt at the federal level — but it
CMS 2026 Medicare Part B premium schedule. Thresholds based on