Medicare Part D

The prescription drug benefit. Sold by private insurers but federally regulated. The 2026 base beneficiary premium is approximately $36.78 per month before IRMAA. Actual plan premiums vary widely. As of 2025 the Inflation Reduction Act capped Part D out-of-pocket at $2,000 per year. Higher-income beneficiaries pay a Part D IRMAA surcharge on top of the plan premium. Part D is optional, but choosing not to enroll triggers a 1 percent per month late enrollment penalty for life if you later join.