Quick Read – Social Security back pay is taxed entirely in the year received, and Medicare’s two-year lookback locks in higher premiums before a warning arrives. – A married couple where both spouses cross one IRMAA tier can face roughly $2,300 in extra annual Medicare costs…
aced to a single lump-sum deposit. – The IRS lump-sum election under IRC Section 86(e) reallocates back pay across prior years, potentially reducing the MAGI spike that triggers IRMAA surcharges. – A 68-year-old who delayed Social Security past full retirement age and claimed six months of retroactive benefits in one check can see that decision follow him into Medicare two years later. If the taxable part of the lump sum lands on top of pension income and a modest Roth conversion, his modified adjusted gross income can cross an IRMAA threshold
For 2026, that can raise his Part B premium from $202.90 to $284.10 and add a $14.50 Part D surcharge. By the time the notice arrives, the tax year that caused the problem is already closed. IRMAA touches only about 8% of Part B enrollees.
For 2026 premiums, the first surcharge starts when 2024 MAGI exceeds $109,000 for single filers or $218,000 for married couples filing jointly. A retroactive Social Security payment does not matter for everyone, but it can be expensive when it stacks on top of pensions, Roth conversions, investment income, or other taxable income in the same year. Are You Ready To Retire, Or Years Behind?