Once an individual’s income surpasses a certain threshold, IRMAA surcharges automatically apply to their Medicare Part B and Part D premiums. Social Security notifies beneficiaries of their IRMAA status in an annual determination letter, usually sent in November or December before the surcharge takes effect in January. Those who believe their IRMAA determination is incorrect can appea... https://www.federalpensionadvisors.com/post/2025-irmaa-brackets