Medicare’s $2,100 annual out-of-pocket drug cap is automatic, but splitting that cost into monthly installments requires enrollees to opt in through their Part D plan before filling the prescription. The Medicare Prescription Payment Plan, or M3P, lets enrollees smooth the $2,100 ceiling into monthly bills, with a January enrollment spreading the full amount into roughly $175 monthly payments. Enrolling after September cuts too few months to matter, and the program only reschedules payments without reducing the underlying drug cost. It also covers only drugs on the plan’s formulary, so verifying coverage first is essential. Plans must process elections within 24 hours, and the election resets each January 1.