What is the Part D late enrollment penalty and how is it calculated?

When you first become eligible for Medicare, you have a window to sign up for a Part D drug plan. If you go 63 or more days in a row without what Medicare calls creditable coverage, meaning coverage at least as good as standard Part D, you'll owe a penalty when you do eventually sign up. The penalty is calculated by multiplying 1 percent of the national base beneficiary premium (a figure Medicare sets each year) by the number of months you went without coverage. That amount is then rounded to the nearest ten cents and added to your monthly Part D premium indefinitely. Because it's tied to a figure that changes annually, the dollar amount of your penalty can actually shift slightly from year to year. What counts as creditable coverage includes most employer plans, TRICARE, VA drug benefits, and others. The key is keeping documentation that your previous coverage was creditable, because Medicare will ask. If you didn't know you needed Part D because you were still on an employer plan, that's fine as long as the coverage qualified. The trouble happens when people skip drug coverage because they don't take prescriptions right now. Medical needs change, and the penalty clock doesn't care about your current health.