the Surcharges Start at $109,000 and Skip Straight to the Top

Read that middle row again. One dollar of MAGI above $109,000 on an MFS return triggers a $446.30 monthly Part B surcharge, the second-highest tier in the entire IRMAA system. A single filer would need to earn more than $205,000 to hit that same surcharge. The MFS filer skips four brackets on the way up.

Part D Compounds the Bill

Part D IRMAA follows the same compressed MFS structure. Above $109,000 MAGI, the Part D surcharge jumps to $83.30 per month, then $91.00 at or above $391,000. That surcharge sits on top of whatever the prescription drug plan itself charges, and Social Security withholds it from the benefit check whether the enrollee pays the base premium directly or not.

For a couple where both spouses are on Medicare and both file separately with MAGI over the first threshold, the household is looking at two full Part B premiums of $649.20 plus two Part D surcharges of $83.30, every month, for the plan year. A joint filer couple at the same combined income (below $218,000) pays zero IRMAA.

The Two-Year Lookback Locks It In

IRMAA uses a two-year income lookback. The 2026 premium is priced off the 2024 tax return. A couple who filed separately in 2024, even for a reason that no longer applies, is paying the MFS surcharge right now and cannot re-file their way out of it. The 2.8% 2026 Social Security COLA does not begin to offset an extra $446 per month per person.

SSA-44 does not help here either. That form applies only when income dropped because of a qualifying life-changing event: work stoppage, work reduction, death of a spouse, marriage, divorce, loss of pension. Choosing MFS is not on the list.

What to Do

• Before filing this year’s return, model both statuses. If either spouse is 63 or older, run the return jointly and separately and compare the combined federal tax plus two years of projected Medicare premiums. The tax savings from MFS often disappears once the IRMAA bill arrives.

• If the reason for filing separately is student loan repayment strategy or spousal liability, price the Medicare cost of that decision explicitly. For many households the IRMAA hit exceeds the loan payment savings.

• If you and your spouse lived apart for the entire tax year, confirm your return reflects that. MFS filers who lived apart all year use the single-filer thresholds, which restore access to the graduated tiers and can cut the surcharge by hundreds per month. Documentation matters if Social Security questions it. Retirees with income near an IRMAA bracket may also want to review the broader set of hidden Medicare bills that show up alongside the surcharge.

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