Medicare Part D

How Income Affects Your 2026 Medicare Part B and D Costs

MOUNT PLEASANT, S.C. — With Medicare's Annual Enrollment Period running through Dec. 7, retirees along the Lowcountry coast are getting a first look at what their 2026 Part B and Part D costs will actually be. For most people, the standard premiums apply. But for a smaller group of higher-income beneficiaries, an extra charge called IRMAA can quietly push monthly costs up by hundreds of dollars — and the trigger point starts lower than many expect.

Higher earners in Mount Pleasant should check their 2026 Medicare bill

Here's what income has to do with your Medicare bill in 2026, and where the thresholds fall.

What IRMAA is, in plain English

IRMAA stands for the Income-Related Monthly Adjustment Amount. It's an extra amount added to your Part B premium (which covers doctor visits and outpatient care) and your Part D premium (which covers prescription drugs) if your income is above a certain level.

A few key points:

• IRMAA is set by the Social Security Administration, not by your insurance company.
• It's based on your Modified Adjusted Gross Income (MAGI) from your tax return two years ago. For 2026, that means your 2024 taxes.
• If you owe it, Social Security sends you a letter explaining the amount and how to appeal.
• The surcharge applies to both Part B and Part D — even if you have a Medicare Advantage plan or a standalone drug plan.

Where the 2026 thresholds start

For 2026, the IRMAA surcharge begins once income crosses $109,000 for a single filer (or roughly double that for a married couple filing jointly). Below that line, you pay the standard Part B premium and no Part D adjustment.

Above the first threshold, the surcharge climbs in tiers. The highest tier applies to individuals with incomes at the top end (generally $500,000 or more for singles, $750,000 for couples filing jointly). Each tier adds a set dollar amount to both your Part B and Part D premiums.

You can see the current year's tiers and dollar amounts on Medicare.gov under "Costs."

Why 2026 matters more than usual

Two things make this year worth paying closer attention to:

1. Part D is being reshaped. Starting in 2026, the annual out-of-pocket cap on prescription drugs rises to $2,100, and the Part D maximum deductible is $615. The old "donut hole" is gone — there are now three phases (deductible, initial, catastrophic). 2. The Medicare Prescription Payment Plan lets you spread your drug costs across the calendar year in monthly installments instead of paying big amounts at the pharmacy counter. It's optional and free to join.

Neither of those changes IRMAA itself, but they do change how the overall drug-cost picture looks — which is worth reviewing during AEP.

What to do if a one-time income spike pushed you over

This is the part many retirees miss. If your income in 2024 was unusually high because of a life-changing event — you retired, a spouse passed away, you sold a business, you got divorced, or you lost a pension — you can ask Social Security to recalculate using your more recent income.

The form is SSA-44, "Medicare Income-Related Monthly Adjustment Amount – Life-Changing Event." You submit it to your local Social Security office with documentation. Selling a house or taking a one-time Roth conversion generally does not qualify, but it's worth asking.

What's happening locally

Mount Pleasant is in Charleston County, where Medicare beneficiaries have a range of Original Medicare, Medicare Advantage, and standalone Part D options available during AEP. Availability is set at the county level, so two neighbors in the same ZIP code will typically see the same menu of plans. IRMAA, on the other hand, is personal — it depends on your tax return, not your address.

If you want to compare what's offered in Charleston County, the official Plan Finder at Medicare.gov lets you enter your ZIP code and your prescription list to see side-by-side details.