- IRMAA
- The income-related monthly adjustment amount: an extra charge added to Medicare Part B and Part D premiums for people with higher incomes. In 2026 it applies when modified adjusted gross income is above $109,000 for an individual return or $218,000 for a joint return, and the Part B premium can reach $689.90 a month.
- Part B standard premium
- The monthly premium most people pay for Medicare Part B (doctor visits, outpatient care). It is $202.90 in 2026 and is usually deducted from Social Security benefits. The 2026 Part B deductible is $283.
- Two-year look-back
- Social Security sets IRMAA from the most recent tax return the IRS provides, usually the one from two years earlier. 2026 premiums are based on 2024 income, so a large Roth conversion, home sale or capital gain can raise premiums two years later.
- Brackets are a cliff
- IRMAA is not phased in. One dollar over a threshold moves you into the next bracket and the full surcharge for that bracket applies. That is why the calculator shows how much income room you have before the next bracket.
- Modified adjusted gross income (MAGI)
- For IRMAA, MAGI is adjusted gross income plus tax-exempt interest income. Qualified Roth IRA withdrawals and HSA withdrawals for medical costs are not included; required minimum distributions and taxable Social Security are.
- Life-changing event (SSA-44)
- If your income has gone down because of marriage, divorce, a spouse's death, stopping or reducing work, loss of income-producing property, or loss of a pension, you can ask Social Security to use a more recent year's income by filing form SSA-44 with proof.
- Part D surcharge
- The IRMAA for prescription drug coverage, from $14.50 to $91.00 a month in 2026. It is paid to Medicare, not to your plan, on top of your plan's own premium, and it applies to stand-alone drug plans and Medicare Advantage plans that include drug coverage.
- Married filing separately
- If you file separately and lived with your spouse at any time during the year, much tighter brackets apply: income above $109,000 goes straight to the second-highest surcharge, and $391,000 or more to the highest. Separate filers who lived apart all year use the individual brackets.