Guide · updated 2026-08-03
Why Your Part B Premium Changed This Year
A Part B premium can move for three entirely separate reasons, and they are routinely mistaken for one another. The standard premium changed, or your income two years ago crossed a threshold, or a rule tied your increase to your Social Security raise. Here is how to tell which one happened.
Reason one: the standard premium itself moved
CMS sets a standard Part B premium each autumn for the following year, in an annual notice. When that figure rises, it rises for everyone paying the standard amount, regardless of income or of what Social Security did. This is the most common cause and the least interesting one — the year-by-year history is published, so it is straightforward to check whether a given year's change was ordinary or unusually large. Nothing about it is specific to you.
Reason two: your income two years ago crossed a threshold
If the tax return filed two years earlier showed income above an income-related threshold, a surcharge is added on top of the standard premium, and on top of the drug-plan premium separately. Because the surcharge is a cliff rather than a slope, this cause produces a step change rather than a gentle one: a premium that jumps noticeably in a single year, with no change in the standard amount, almost always means a threshold was crossed by the return from two years back.
Reason three: the hold-harmless rule tied your increase to your raise
For most people who have their premium deducted from a Social Security payment, a statutory provision prevents the dollar increase in the Part B premium from exceeding the dollar increase in that year's cost-of-living adjustment. In a year with a small raise and a larger premium increase, that provision holds the premium down and different people end up paying different amounts for the same coverage. It does not apply to everyone: people paying an income-related surcharge, people newly enrolled that year, and people billed directly rather than by deduction are all outside it.
How to work out which one applies to you
Start with the published standard premium for both years. If your old and new premiums both match the standard figures, it was reason one. If your new premium is the standard figure plus a surcharge amount, look at the return from two years before that year — reason two. And if your increase is a smaller dollar amount than the standard premium rose by, and it happens to equal the dollar increase in your Social Security payment, that is the hold-harmless provision at work.
Official sources for this guide
Now do the math →
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