About 8 percent of people with Medicare pay more than their chosen drug plan’s own premium because of a separate, income-based surcharge layered on top of it. The extra amount, formally called the Part D Income-Related Monthly Adjustment Amount, is not set by the insurance company selling the plan and does not vary by which plan a person picks. It is calculated by Social Security using a tax return filed two years earlier and applies no matter how modest the underlying plan premium is.
How the Part D Surcharge Is Calculated
The surcharge kicks in once modified adjusted gross income on a Medicare beneficiary’s tax return from two years earlier exceeds $109,000 for an individual filer or $218,000 for a married couple filing jointly. Below those thresholds, a beneficiary pays only the premium their specific Part D plan charges, with no add-on at all.
The surcharge scales in five steps for 2026, from an extra $14.50 a month at the lowest bracket up to an extra $91.00 a month at the highest, reserved for individual income above $500,000 or joint income above $750,000. Because it is added on top of the plan’s own premium rather than replacing it, someone in the $91-a-month bracket who also picked an expensive drug plan pays both amounts in full.
The five-step scale is designed so the surcharge grows roughly with income, but the jump between brackets is a cliff rather than a gradual slope. A dollar over a bracket’s ceiling in reported income triggers the entire next surcharge tier for the full year, not a prorated amount somewhere between the two.
Social Security sets the surcharge the same way regardless of whether a beneficiary gets Part D through a standalone prescription drug plan or through a Medicare Advantage plan that bundles in drug coverage. Choosing a Medicare Advantage plan instead of Original Medicare with a separate Part D plan does not avoid the surcharge; the income-based add-on follows the person, not the type of plan carrying the drug benefit.
The 2026 Income Tiers
A married couple filing separately faces a narrower scale: income up to $109,000 pays no surcharge, income between $109,000 and $391,000 pays an extra $83.30, and income at or above $391,000 pays the full $91.00. That structure reaches the top tier at a far lower income than either the single or jointly-filing scales, a quirk built into how the separate-filing brackets are set.
The surcharge is a separate concept from the Part D late enrollment penalty, which punishes a gap in drug coverage rather than a level of income. A high earner who enrolled on time and never had a coverage gap can still owe the income surcharge, while a low earner who went years without drug coverage can owe the enrollment penalty without ever owing this surcharge at all.
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Why It’s Billed Separately From The Plan
Because Social Security determines the surcharge, not the drug plan, it never shows up on the bill the plan sends. Instead, the amount is deducted directly from a beneficiary’s Social Security, Railroad Retirement, or Office of Personnel Management benefit payment, on top of whatever is already withheld for the plan premium itself.
Someone who does not collect any of those benefits, or whose surcharge is larger than the benefit payment itself, gets a separate bill from Medicare, not from the drug plan and not from Social Security. Medicare’s guidance is explicit that this bill has to be paid directly to Medicare to keep Part D coverage active, since sending the payment to the plan by mistake does not count as paying the surcharge.
The billing can lag the calendar year in a way that surprises people. Medicare starts sending these separate bills in December for the following year, but a beneficiary who is first billed after January owes the surcharge for every month already elapsed at that point, not just going forward, so a delayed first bill can arrive as a larger lump amount.
A beneficiary whose income dropped after the tax year used to calculate the surcharge, because of retirement, a spouse’s death, divorce, or a similar life-changing event, can ask Social Security to use more current income instead, through a form called SSA-44, rather than waiting two years for the surcharge to catch up with the lower income on its own.
The Money That Depends On A Form
The Part D income surcharge is a Social Security calculation, not a program a household applies for, and appealing it depends on filing the right form rather than searching for a benefit to sign up for. Other Medicare-linked costs work the opposite way: money that sits unclaimed until someone actually files for it.
A 69-page guide covers the SSA-44 appeal as an appendix alongside all 11 separate assistance programs, their 2026 income limits, and a 50-state phone directory for the office handling each one.
Read The Benefits Checklist to see which of those programs a household might already qualify for.
This article was researched and drafted with AI assistance and reviewed against primary sources before publication.
