Why does age 63 matter for Medicare premiums?
Medicare looks at your income from two years earlier, so what you earn at 63 and 64 can set your first Medicare premiums at 65 and 66.
The short answer
Social Security sets your IRMAA, the income-based surcharge on Medicare Part B and Part D, from a tax return filed two years before the premium year. Premiums in 2026 are generally based on your 2024 return. If you turn 65 and start Medicare in 2026, your very first premiums are decided by what you earned in the year you were 63.
The timeline if you start Medicare at 65
| Income earned at age | Sets your Medicare premiums at age |
|---|---|
| 63 | 65 |
| 64 | 66 |
| 65 | 67 |
The rule is about tax years, not birthdays. Age 63 is a shorthand for people who start Medicare right at 65. If you delay Medicare, each premium year still looks back two years: premiums you pay in 2028 are based on your 2026 return.
What this means for planning
- Before 63: income generally cannot raise your Medicare premiums if you start at 65. It still counts for income tax and, if you buy marketplace insurance before 65, for your health insurance subsidy.
- At 63 and 64: a large one-time amount, such as a Roth conversion, a big capital gain or a lump-sum payout, can lift your first two years of premiums. These amounts are part of adjusted gross income, which is what IRMAA uses.
- Use today's lines as a guide only. The income lines are adjusted every year, so the 2026 figures are an approximation of where the lines will sit when you reach 63.
If your income falls when you retire
If you retire at 65 but are still billed on a working income from two years back, you can ask Social Security to use a more recent year after a life-changing event. See how to appeal an IRMAA surcharge.
Check which IRMAA tier an income falls in → · Roth conversions before Medicare →
Common questions
Does income before age 63 affect my Medicare premiums?
For most people who start Medicare at 65, no. Premiums are generally based on the return from two years earlier, so income before 63 is not used. It can still affect your income tax and any marketplace subsidy.
What if I delay Medicare past 65?
The same two-year rule applies to whichever year you pay premiums. For example, premiums you pay in 2028 are based on your 2026 tax return.
Is the 2026 income line the one that will apply to me at 63?
Probably not exactly. The lines are adjusted each year, so use the current lines to estimate, then re-check closer to the year that matters.
Keep reading
Sources: SSA: Medicare premiums; CMS: 2026 Part B premiums and IRMAA; SSA POMS HI 01101.010: Modified Adjusted Gross Income