Quick Read – One dollar over the $109,000 MAGI threshold locks in a $1,148 annual Medicare surcharge calculated from tax returns filed two years earlier. – Tax-exempt municipal bond interest counts toward IRMAA’s MAGI, pushing a retiree with $108,400 AGI and $900 in muni…
terest past the threshold. – Widowed spouses face a filing-status trap where income safely inside the $218,000 joint bracket can suddenly exceed the $109,000 single threshold. – Fewer than one in ten Medicare beneficiaries pays an Income-Related Monthly Adjustment Amount, so a reader whose household income sits well under the first tier can stop here. Everyone else should keep reading
The first tier catches a single filer whose 2024 modified adjusted gross income tops $109,000, or a joint filer above $218,000, and it adds a 2026 surcharge to both Part B and Part D premiums. The Scenario A 67-year-old retiree files a single return for tax year 2024. Her adjusted gross income reads $108,400.
She also collected $900 in tax-exempt municipal bond interest, which she assumed stayed invisible because it escapes federal income tax. The Social Security Administration adds that line 2a interest to her line 11 AGI, arrives at $109,300 of MAGI, and drops her into the first IRMAA bracket for 2026. Her January 2026 premium notice lands higher than she expected, and the surcharge rides every monthly premium for the rest of the year.