He Will Amend His 2024 Return and Get a Refund. Social Security Will Keep Pricing His 2026 Medicare Premium on the Original Numbers Until He Mails Them the Amended Return Himself
The IRS processed his amended return, sent the refund, and closed the case. Medicare kept charging him the surcharge anyway, and fixing that requires a completely separate trip that most retirees never know to make.
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A retiree finds out his 2024 tax return overstated his income. He files an amended return, the IRS agrees, and a refund comes. But every month his Social Security deposit still loses a Medicare surcharge based on the old, wrong number. The IRS and Social Security keep separate records. The correction reaches Medicare only if he takes it there himself.
This affects a small group. IRMAA surcharges apply to roughly 8% of people with Part B, according to CMS. A single filer whose corrected income is well under $109,000 pays the standard $202.90 monthly premium and no surcharge. The person who needs this fix is someone whose original return pushed him over a line his real income never reached.
IRS Refund and Medicare Premium Run on Separate Tracks
Medicare sets the 2026 IRMAA using 2024 tax data that the IRS supplies to Social Security. That data reflects the original return. When the IRS processes his amendment and sends the refund, Social Security keeps the premium it already set.
Social Security can use an amended return instead of the tax data already on file when the beneficiary asks for a new determination and provides proof from the IRS. He generally has three calendar years after the tax year closes to make that request. The rule works both ways: Social Security can use the amended figures even when they raise, not lower, his premium.
This is a different path from Form SSA-44, which asks Social Security to use a newer, lower year of income after a life-changing event such as retirement, divorce or a spouse’s death. An amended return corrects the 2024 income figure itself. He needs only proof that the IRS accepted the correction.
Corrected MAGI Has to Cross the Line
For IRMAA, modified adjusted gross income (MAGI) equals adjusted gross income (AGI) plus tax-exempt interest. When the Social Security Administration (SSA) processes an amended return, it uses the corrected AGI and tax-exempt interest for that year. That means municipal bond interest counts even though the IRS never taxes it.
Say an error raised his 2024 MAGI to $145,000 as a single filer, and the amended return corrects it to $105,000. Under the 2026 CMS brackets:
| Return | 2024 MAGI (single filer) | Part B IRMAA (monthly, per person) | Total Part B Premium (monthly, per person) |
|---|---|---|---|
| Original | $145,000 | $202.90 | $405.80 |
| Amended | $105,000 | $0.00 | $202.90 |
The original figure falls in the second level, which covers single filers above $137,000 and up to $171,000. That level doubles his Part B premium. The Part B surcharge alone costs $2,434.80 a year. A Part D surcharge comes on top of that. At $145,000 of MAGI, it adds another $37.50 a month in 2026. The corrected figure places him below the first threshold, so he pays no surcharge at all (IRMAA ranks among the Medicare traps that quietly add up, and we covered the rest in a free guide to Medicare’s hidden bills).
A refund on its own tells Medicare nothing. If the refund came from a missed tax credit or a withholding fix, AGI remains the same and so does the surcharge. Only a lower AGI or lower tax-exempt interest changes the MAGI Medicare uses, and the correction has to cross an IRMAA bracket to change the bill. If his corrected MAGI stays inside the same tier, his surcharge stays there too.
What to Bring Social Security
- Amended return. His own copy of the 2024 Form 1040-X.
- IRS proof. An IRS receipt letter, an IRS transcript or a copy of the amended return from the IRS. These are the forms of evidence SSA’s manual lists. A bank deposit from the refund is not on that list.
- His 2026 IRMAA notice. This shows the income figure Social Security is using now.
- A specific request. He should ask for a new IRMAA determination based on the amended tax information. SSA tells people with amended returns to call 800-772-1213.
Check the Months He Already Overpaid
When Social Security accepts the corrected income, the new decision letter should give the revised premium and the months it applies to. He should check that the correction reaches every 2026 month for which the wrong IRMAA was charged.
Next, he will want to compare his monthly deposits with the letter. The extra premium already taken out should come back as a refund or a credit. If his deductions still reflect the $405.80 premium two payment cycles later, he should call again with the letter in hand. He should keep the amended return, IRS transcript, revised notice and refund records in one file.
He might want to check his 2025 return. Medicare will set 2027 premiums from 2025 income, so if the same mistake shows up there, the surcharge comes back next year unless he amends that return too.
An amended return can fix the income Medicare uses. But the fix only takes effect once it goes from the IRS record into Social Security’s premium calculation, and he is the one who has to make that happen.
Contact [email protected] for any questions or corrections.
Gerelyn Terzo is the author of dividend investing handbook "Dividend Investing Strategies: How to Have Your Cake & Eat It Too." A veteran financial journalist, she covers agri-finance for outlets like Global AgInvesting and the broader stock market and personal finance for 24/7 Wall Street. She began at CNBC and later helped launch Fox Business in New York. Gerelyn currently resides in Woodland Park, Colorado and dabbles in nature photography as a hobby.
